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| Muscle diseases after physical activity, causes and pathogenesis. What is the differential diagnosis for muscle hypotonia? Mineral or enzyme deficiency |
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Head of Zhusina
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kidneys (although it does not prevent the occurrence of Cushing's syndrome). When taking twice the daily dose every other day, adrenal suppression, Cushing's syndrome and decreased resistance to infections are less likely to develop. This regimen is effective for most neuromuscular diseases.
6.1. Progressive muscular dystrophies
The term “muscular dystrophy” refers to a group of clinically polymorphic genetically determined diseases, which are based on primary progressive degenerative changes in muscle fibers. Various forms of myodystrophies differ from each other in their genetic nature, type of inheritance, timing of onset, and topographical peculiarity of the distribution of muscle atrophies. A characteristic clinical marker of myodystrophies is a “duck” gait associated with weakness of the gluteal muscles, which fix the pelvis relative to the femur. As a result, during walking, a tilt of the pelvis towards the non-supporting leg (Trendelenburg phenomenon) and a compensatory tilt of the torso in the opposite direction (Duchenne phenomenon) occur. In addition, patients may experience walking on their toes, frequent falls, slow motor development, and specific limitations when raising their arms, climbing stairs, and getting up from the floor.
Duchenne and Becker muscular dystrophies. The Duchenne form is widespread in the world and occurs with a frequency of 1 in 3500 newborn boys, while the Becker form is observed approximately 3-5 times less often.
Etiology and pathogenesis. Duchenne and Becker muscular dystrophies are allelic variants, inherited in an X-linked recessive manner and are caused by either a complete absence of synthesis or the synthesis of a defective high-molecular-weight cytoskeletal protein, dystrophin. Due to the lack of dystrophin, myofibrils lose resistance to cyclic acts of contraction-relaxation and rupture. Sarcoplasmic membranes become unstable, the functioning of ion channels is disrupted, resulting in an increase in the concentration of free intracellular ionized calcium, which has a necrotizing effect on muscle fibers, causing their lysis (Fig. 6.2).
Clinical picture. The first clinical symptoms in most boys with Duchenne muscular dystrophy occur before 3-5 years of life: gait is impaired, children begin to fall frequently, lose
Rice. 6.2.Molecular organization of dystrophin
Rice. 6.3.Patients depicted by G. Duchenne
mobility. The developing pseudohypertrophy of the calf muscles creates a misleading impression of muscle strength (Fig. 6.3). Pseudohypertrophy can also develop in the gluteal, deltoid, abdominal and tongue muscles. Finally, muscle weakness becomes so obvious that the child has difficulty getting up from the floor, walks with a “duck” gait, and uses myopathic techniques: “climbing on one’s own,” “climbing with a ladder” (Gowers’ symptoms).
Rice. 6.4.1.5 year old child with Duchenne disease
Rice. 6.5.The same child at 5 years old. Muscle pseudohypertrophy, lordosis
Motor functions become relatively stable between 3 and 6 years of age. In most cases, the ability to walk and climb stairs continues until the age of 8. From 3 to 8 years, further shortening of the Achilles tendons occurs and fixed flexion contractures are formed in the ankle joints, compensatory lumbar hyperlordosis, kyphoscoliosis of the thoracic spine develop, atrophy of the muscles of the thigh, pelvic, and then the shoulder girdle, back and proximal arms increases. Noteworthy is the presence of “loose shoulder girdles,” “wing-shaped shoulder blades,” and a “wasp waist.” Often muscle atrophy is masked by a well-developed subcutaneous fat layer. Deformities often develop chest and stop, diffuse osteoporosis. The knee, flexion and extension of the elbow reflexes disappear first, while the Achilles reflexes can persist for quite a long time. At the age of 9, some children already move with the help of a wheelchair, but most children retain the ability to move independently until they are 12 years old, and the ability to stand until they are 16 years old. Weakness of the respiratory muscles and diaphragm causes a decrease in the vital capacity of the lungs to 20% of normal, which leads to episodes of nocturnal hypoventilation (Fig. 6.4-6.6).
Some patients exhibit various signs of endocrinopathy: adiposogenital syndrome, short stature. Due
Rice. 6.6.The same child at 14 years old. Spinal deformation, flexion contractures, and muscle atrophy are evident
Rice. 6.7.Pseudohypertrophy of the leg muscles in Becker's disease
With a deficiency of cerebral isoforms of dystrophin - apodystrophins, some patients with Duchenne muscular dystrophy have mental retardation of varying degrees. The severity of mental disorders in children does not correlate with the severity of the muscle defect and the stage of the myodystrophic process. An obligatory sign of the advanced stage of Duchenne muscular dystrophy is hypertrophic, or dilated, cardiomyopathy, which is accompanied by cardiac arrhythmias, expansion of its boundaries, and symptoms of heart failure. Cardiomyopathy is the most common cause of death in Duchenne muscular dystrophy. Respiratory failure, which is provoked by intercurrent infections or aspiration, also leads to mortality. Patients die in the 2-3rd decade of life.
Becker's muscular dystrophy (Fig. 6.7) can develop after 15-
20 years, progresses much more smoothly. Patients with this form of muscular dystrophy live into adulthood. Intellectual impairment is not typical for her, tendon retractions and contractures are less pronounced than with Duchenne muscular dystrophy, cardiomyopathy may be absent. However, in some patients, cardiac dysfunction comes to the fore and is often a manifest symptom of the disease. In addition, some patients with Becker muscular dystrophy have preserved fertility, so adult patients through their daughters can transmit the disease to their grandchildren (“grandfather effect”).
Diagnostics.Duchenne muscular dystrophy is characterized by a significant increase in enzyme levels already in the early stages of muscular dystrophy.
physical process. In patients under 5 years of age, the level of creatine phosphokinase (CPK) can exceed the upper limit of normal by tens or even hundreds of times. The enzyme concentration then decreases by approximately 20% per year. The serum levels of aldolase, lactate dehydrogenase, and transaminases are also increased. High CPK activity is an almost obligate sign of the disease and, in addition to Duchenne myodystrophy, can occur with Becker muscular dystrophy (usually not exceeding 5000 U/l), polymyositis, dermatomyositis, hypothyroidism, alcoholic myopathy and paroxysmal myoglobinuria. EMG reveals signs of primary muscle damage (low-voltage curve with an abundance of polyphasic potentials, shortening of motor unit action potentials).
Currently, the generally accepted “gold standard” for diagnosing Duchenne and Becker muscular dystrophy, identifying gene carriers and prenatal diagnosis is mutation analysis. The immunohistochemical reaction for dystrophin is used to analyze the percentage of dystrophin in muscles and distinguishes the Duchenne and Becker forms (in the first it is absent). In heterozygous carriers (mothers and sisters of patients), in approximately 70% of cases, subclinical signs of skeletal muscle pathology are detected: increased CPK, primary muscle changes on EMG and in the study of muscle biopsies. Occasionally, carriers experience thickening and increase in volume of the calf muscles, increased muscle fatigue during physical activity, and muscle spasms after exercise (cramps).
X-ray of bones helps to detect atrophy of the diaphysis of long tubular bones, thinning of the cortical layer, narrowing of the osteoarticular canal, and diffuse osteoporosis.
Damage to the cardiovascular system (cardiomyopathy) develops in 73% of sick children. Dystrophin deficiency in cardiomyocytes leads to progressive atrophy of cardiomyocytes and their replacement with fibrous tissue. Cardiomyopathy is first diagnosed at 6-7 years of age; by the age of 20, it is present in 95% of patients. Tachycardia, arrhythmia, lability of pulse and blood pressure, muffled sounds, and expansion of the boundaries of the heart are also noted. The ECG shows heart rhythm disturbances, ventricular extrasystoles, signs of left ventricular hypertrophy (27%): deep wave Q in leads II-III aVF and V 6; high R in lead V 1, signs of myocardial ischemia (5%). Echo-CG can reveal hypertrophic (55%) or dilated
(25%) cardiomyopathy, atrial septal defect, mitral valve prolapse, left ventricular myxoma.
A cardiac muscle biopsy reveals muscle fiber atrophy, interstitial fibrosis, and fatty infiltration.
Differential diagnosis of Duchenne and Becker muscular dystrophy is carried out with congenital dysplasia of the hip joints, vitamin D-resistant rickets, proximal types of spinal amyotrophies, polymyositis and dermatomyositis, metabolic and endocrine myopathies.
In the presence of a clinical phenotype of Duchenne muscular dystrophy in girls, the presence of X-autosomal translocations or other chromosomal aberrations involving the X chromosome, as well as some other rare genetic variants, should first be excluded. In addition, it is necessary to exclude Shereshevsky-Turner syndrome (X-monosomy). For this purpose, a cytogenetic study of the karyotype is carried out.
Emery-Dreyfus muscular dystrophy is a slowly progressive form of myodystrophy with an X-linked recessive type of inheritance, which is caused by a mutation in the gene of the cytoskeletal muscle protein - emerin, produced mainly in skeletal, smooth muscles and cardiomyocytes.
Clinical picture (Fig. 6.8). The disease begins between 5 and 15 years of life. The earliest and most typical symptoms are increasing flexion contractures in the elbow joints and wrist extensors, and retraction of the Achilles tendons. As a rule, at the age of 12, patients already have significantly pronounced contractures in the knee, ankle and elbow joints. Then there is weakness and atrophy of the biceps and triceps muscles of the shoulder, and later - the deltoid and other muscles of the shoulder girdle. In some cases, the first symptom is walking on the toes and outer edges of the feet, which occurs around 5 years of age. Until this point, the motor development of children is usually not impaired. Muscle weakness occurs unnoticed and progresses slowly. At about 20 years of age, relative stabilization occurs. The ability to walk and climb stairs is preserved. The facial muscles are not affected. Muscle weakness is present in the arms (scapulohumeral) and legs (peroneal). Gowers maneuvers and pseudohypertrophy of the gastrocnemius muscles may be absent. Tendon reflexes are not evoked. The posterior cervical muscles are often shortened and there is a restriction
Rice. 6.8.Patient 12 years old with Emery-Dreyfus muscular dystrophy
movements in the cervical spine (rigid spine syndrome). Frequent and prognostically important symptoms of the disease are cardiac conduction disturbances and developing dilated or hypertrophic cardiomyopathy. Cardiomyopathy may be complicated by the development of atrial paralysis due to fibrosis of the sinus node pacemakers. In these cases, urgent implantation of an artificial pacemaker is indicated.
Syncope and attacks of bradycardia in some cases may precede the onset of muscle weakness, but more often occur in the 3rd decade of life. Changes in the conduction system of the heart are not always detected during a standard ECG study, but monitoring can reveal atrioventricular blockades and Samoilov-Wenckebach periods. Arrhythmia that cannot be corrected by implantation of an artificial pacemaker can lead to stroke and death of the patient. The vital prognosis for Emery-Dreyfus muscular dystrophy depends entirely on the degree of heart damage.
Diagnostics.The activity of CPK was moderately increased, lactate dehydrogenase and aldolase - to a lesser extent. Emery-Dreyfus muscular dystrophy is supported by the absence of an immunofluorescent reaction to emerin with 12 monoclonal antibodies during biomicroscopy of leukocytes, muscle and skin biopsies. The disease is characterized by combined EMG signs of primary muscular and neurogenic lesions with a high prevalence of spontaneous denervation activity.
Facioscapulohumeral myodystrophy (Landouzy-Dejerine type). The disease is inherited in an autosomal dominant manner with high penetrance and variable expressivity. Occurs with a frequency of 2.9 per 100,000 population. The genetic heterogeneity of facioscapulohumeral myodystrophy has been established. Most cases are associated with a mutation in the long arm of chromosome 4.
Clinical picture. The disease usually begins in the 2nd decade of life. Initially, atrophy is observed in the shoulder girdle, later spreading to the face. Patients have poor facial expressions; speech becomes unintelligible. At the height of the disease, the orbicularis oris and ocular muscles, pectoralis major, serratus anterior and lower trapezius muscles, latissimus dorsi, biceps and triceps brachii muscles are affected. Characteristic symptoms are noted in the form of a “transverse smile” (“Gioconda smile”), protrusion of the upper lip (“tapir lip”). The chest is flattened in the anteroposterior direction, the shoulder joints are rotated inward, and the shoulder blades acquire a wing-like shape. Atrophy spreads in a downward direction. When the leg muscles are involved in the process, weakness is most noticeable in the peroneal muscle group - “foot drop”. Asymmetry of atrophy is characteristic. Muscle pseudohypertrophy may be observed. Contractures and tendon retractions are moderately expressed. Cardiomyopathy is rare. Anomalies of retinal vessels during angioretinography are considered as one of the phenotypic manifestations of the disease. Severe eye symptoms are accompanied by telangiectasia, edema and retinal detachment. Hearing loss may occur. Telangiectasia is eliminated by coagulation, which prevents the development of blindness. The course of the disease is relatively favorable. Physical overload, intense sports activities and irrationally conducted physical therapy can contribute to a more severe course of the disease. Many sick
remain functional and their quality of life does not deteriorate. Other patients are confined to a wheelchair by the disease in adulthood.
Diagnostics.The level of CPK can increase 5 times. EMG records both myopathic motor units and denervation potentials. In many limb muscles, histological changes are minimal; progressive degeneration and marginal denervation are found in the suprascapular muscles. It is necessary to exclude myasthenia gravis and brain stem tumor.
Limb-girdle myodystrophies (CPMD) - cases of proximal muscle weakness, which begins to develop in the 2nd or 3rd decade of life, slowly progresses and leads to deep disability only after 15-20 years.
Etiology and pathogenesis. CMMD is not genetically homogeneous; To date, about 10 different genetic defects have been discovered.
Clinical picture. The muscles of the shoulder and pelvic girdle are the first to be affected. In advanced stages, the muscles of the back and abdomen are significantly affected, and lumbar hyperlordosis is formed. The facial muscles, as a rule, are not affected. Patients exhibit a typical “duck” gait and myopathic techniques. Contractures and pseudohypertrophy of muscles are uncharacteristic. Cardiomyopathies do not develop; intelligence is preserved. Men and women are affected equally often. Death may occur from pulmonary complications.
Diagnostics.The content of CPK is moderately increased. The EMG shows signs of a primary muscle lesion. CMMD must be distinguished from Becker myopathy, juvenile spinal amyotrophy, glycogen storage myopathy, endocrine, toxic, drug-induced myopathies, polymyositis, and myositis.
6.2. Congenital structural myopathies
Congenital structural myopathies (SCM) are a genetically heterogeneous group of slowly progressive skeletal muscle diseases. The clinical symptoms of various SCMs are nonspecific. The main clinical symptom is diffuse muscle hypotonia, which can occur in utero and cause rare fetal movements. SCM has a significant share among the causes of the so-called floppy child syndrome. Hypotonia prevails in the muscles of the pelvic girdle and pro-
simal parts of the legs. The muscles of the shoulder girdle and arms are affected to a lesser extent. Congenital dislocation of the hip, dolichocephalic head shape, Gothic palate, cauda equina, kyphoscoliosis, and muscle hypoplasia are often detected. Delayed motor development is characteristic: children begin to hold their heads up, sit, stand up, walk late, often fall when walking, and are unable to run. In the future, they cannot perform the simplest gymnastic exercises or participate in outdoor games. Tendon reflexes in patients may be normal, reduced or absent. An extremely important criterion for SCM is the absence of progression or very slow increase in muscle weakness. In some forms, motor functions may improve somewhat with age.
Diagnostics.CPK activity is normal or slightly increased. EMG records low-amplitude polyphasic myopathic potentials of motor units. The speed of impulse conduction along motor and sensory fibers is normal. The diagnosis is reliably established only by performing a muscle biopsy using light and electron microscopy, which reveals the specific structure of the muscle fiber. The study of muscle biopsies from sick children can reveal unique histological features that have determined a number of names: central core disease, myotubular myopathy, nemaline myopathy, three-lamellar myopathy, myopathy with lysis of type I fibers, myopathy with spherical bodies, myopathy with accumulation of bodies in the form of “fingerprints” fingers", myopathy with cytoplasmic inclusions in the form of reduced bodies, myopathy with tubular aggregation, etc.
Treatment of muscular dystrophies. Therapeutic options for myodystrophies are significantly limited. There is practically no etiological and pathogenetic treatment. Symptomatic treatment is aimed at maintaining existing muscle strength for as long as possible, reducing the rate of development of atrophy and preventing the formation of contractures. The main task is to extend the period of activity for as long as possible.
Complex treatment consists of drug therapy, physiotherapeutic procedures, therapeutic exercises and massage, orthopedic correction and diet. Psychological support, continued education, and proper professional guidance play an important role.
Physiotherapeutic procedures include electrophoresis of proserine, calcium chloride, sinusoidally modulated or diadynamic currents of various penetrating abilities, electrical myostimulation, ozokerite, paraffin and mud applications, baths (radon, pine, sulfur, hydrogen sulfide). Oxybarotherapy is recommended, since oxygen inhibits the processes of fibrosis and collagen formation. Orthopedic correction of conservative (special splints and styling) and operational nature(achillotomy, myotomy) is aimed at combating contractures and emerging pathological alignments of the limbs and also aims to preserve the patient’s ability to move independently. In each case, it is necessary to individually weigh the expected benefits and possible harm from surgery. For developing contractures after thermal procedures, it is recommended to carefully stretch the muscles up to 20-30 times a day, followed by applying a splint while sleeping.
The patient is recommended to eat a diet enriched with protein, limiting fats (especially of animal origin) and carbohydrates with an optimal and balanced content of vitamins and microelements. It is necessary to avoid salty, fried, spices, marinades, strong meat broths, coffee, chocolate, cocoa, cakes, and pastries.
Drug therapy aims to compensate for the energy deficit in muscle tissue, improve tissue metabolism and blood circulation, and stabilize muscle fiber membranes. Nicotinic acid, vitamins B6, B12, A and E (aevit) are used. To improve protein synthetic processes, amino acid preparations (cerebrolysin, glycine, methionine, glutamic, folic acid) are used. Non-steroidal anabolic drugs (potassium orotate), macroergic drugs (phosphaden), cardiotrophics (riboxin, carnitine chloride, solcoseryl), drugs that improve peripheral circulation (trental, halidor, teonicol, oxybral) and nootropics [pantogam, piracetam (nootropil)] are prescribed. To improve the energy processes occurring in the mitochondrial respiratory chain system, coenzyme Q10 (ubiquinone), lymantar, and intravenous infusions of cytochrome-C are used. The effects of detoxification and improvement of the rheological properties of blood, relief of slide syndrome are achieved by infusions of vasoactive drugs, rheopolyglucin, and plasmapheresis courses. Low doses of prednisolone contribute to the relative stabilization of cell membranes. For correction
cardiomyopathies use cardiotrophics (except for patients with hypertrophic cardiomyopathy); for heart failure - cardiac glycosides, diuretics, captopril. For cardiac arrhythmias, quinidine, β-blockers, and calcium antagonists are prescribed. With the development of complete atrioventricular block, the question of the advisability of implanting an artificial pacemaker becomes relevant.
Prospects for the development of genetic therapy methods for some muscular dystrophies (Duchenne, Becker diseases) are associated with the improvement of genetic technologies. There is an active search for genetic carriers (vectors) capable of inserting the dystrophin gene or mini-genes into the muscle cells of a sick recipient. Exceptional importance is attached to medical and genetic counseling of the family, prenatal diagnostics with fetal DNA testing.
6.3. Spinal muscular amyotrophy
Spinal muscular amyotrophy (SMA) is a heterogeneous group of inherited diseases of the peripheral nervous system. Pathogenesis is associated with progressive degeneration of motor neurons in the anterior horns of the spinal cord (in some cases, motor nuclei of the brain stem). The reason for this is a genetic defect that causes programmed cell death - cell apoptosis. Loss of motor neurons leads to the development of flaccid paralysis and denervation atrophy of striated muscles. In most cases, there is symmetrical damage to the proximal muscles of the limbs; distal amyotrophy, bulbar lesions
bar muscles and asymmetry of the lesion develop less frequently. The central motor neuron is usually intact. There are no sensitivity disorders.
Different variants of SMA differ in the age of onset, the nature of the course, the topography of damage to the skeletal muscles and the type of inheritance (Fig. 6.9). Most forms are inherited in an autosomal recessive manner. Several forms are characterized
Rice. 6.9.Floppy baby syndrome in SMA
autosomal dominant and X-linked recessive modes of inheritance. Histological examination of muscle biopsies reveals that small muscle fibers, bundles of hypertrophied and atrophic muscle fibers are adjacent to groups of fibers of normal size.
If the EMG reveals undeniable symptoms of SMA, a muscle biopsy is not necessary. The principles of treatment and rehabilitation of SMA are the same as for myodystrophies. Etiotropic and pathogenetic treatment has not yet been developed.
Proximal spinal amyotrophies of childhood are inherited in an autosomal recessive manner. There are three phenotypically different variants, differing in the age of clinical manifestation, course and prognosis:
Type I, or acute malignant infantile Werdnig-Hoffmann SMA;
Type II, or chronic infantile SMA (intermediate type);
Type III, or juvenile Kugelberg-Welander SMA.
They are based on a single genetic mutation - deletion of the motor neuron viability gene, located on the long arm of chromosome 5. The search for mutations is carried out during DNA diagnostics, including in the fetus during prenatal diagnosis, which helps to avoid the birth of a sick child.
Acute malignant infantile spinal amyotrophy (Werdnig-Hoffmann disease, or SMA type I) occurs with a frequency of 1 in 25,500 newborns. Clinical symptoms are noted at birth or appear before 6 months of life. Even in utero, sluggish movement is noted, indicating a decrease in the motor activity of the fetus. A sick child exhibits generalized weakness, mainly in the proximal muscle groups, hypotonia and areflexia. In the supine position, a “frog pose” is observed with abduction and external rotation of the hips. The facial muscles are relatively intact, the extraocular muscles are not involved. Respiratory function is initially adequate. Atrophy and fasciculations in the tongue, fascicular tremor of the hands are detected. With the development of bulbar syndrome, the pharyngeal reflex disappears, feeding becomes significantly more difficult, which can lead to aspiration pneumonia. A deformity of the chest often develops (Fig. 6.10). If muscle weakness
Rice. 6.10.Child, 6 months, with Werdnig-Hoffmann disease
is detected immediately after birth, death occurs at approximately 6 months of age, while if the first symptoms appear after 3 months of life, the survival period can be about 2 years. The main cause of death is respiratory failure due to intercurrent respiratory diseases (Fig. 6.11, 6.12).
For diagnosis, a gene mutation is detected by molecular genetic analysis. CPK concentrations are usually normal, but may be slightly elevated in children with rapidly progressive weakness. EMG reveals fibrillation and fasciculation potentials at rest and an increase in the mean amplitude of motor unit potentials. The conduction velocity along the motor axons of peripheral nerves is usually normal. SMA type I must be differentiated from other conditions that cause floppy baby syndrome. These include congenital myodystrophies and neuropathies, structural myopathies, congenital or neonatal myasthenia, metabolic myopathies, intrauterine poliomyelitis, botulism, chromosomal pathology, atonic form of cerebral palsy, Marfan syndrome.
Chronic infantile spinal amyotrophy (SMA type II). Muscle weakness usually appears between the 6th and 24th months of life. The earlier the symptoms debut, the more malignant the course. Initial manifestations of weakness are usually symmetrical and are observed in the proximal muscle groups of the limbs. Weakness of the thigh muscles is the most noticeable symptom. In the early period, distal muscle weakness is minimal or absent. Tendon reflexes from the affected muscles are sharply reduced. All patients are able to sit, most can stand independently, and some can even walk (Fig. 6.13). Facial muscles
Rice. 6.11.Boy, 5 years old, with Werdnig-Hoffmann disease
Rice. 6.12.Boy, 3 years old, with Werdnig-Hoffmann disease
Rice. 6.13.Girl, 9 years old, with Kugelberg-Welander disease
and the external muscles of the eye are not affected in the early stages of the disease. Muscle weakness progresses slowly. In some cases, it remains stable for many years, and then progression resumes. Patients are expected to survive until adulthood, but even during the period of relative stabilization, EMG reveals
fibrillation and fasciculation potentials. Contractures and equinovarus deformity of the feet are formed. Already in infancy, children experience spinal curvature, chest deformities, and hip dysplasia.
Diagnostics.CPK concentration is normal. The results of genetic analysis and EMG data are the same as for the acute infantile form.
Juvenile spinal amyotrophy (Kugelberg-Welander disease, or SMA type III) occurs in the general population with a frequency of 1.2 per 100,000. Motor activity in the prenatal period is sufficient; The child is healthy at birth. The onset of symptoms occurs between the 2nd and 15th year of life. Children begin to walk unsteadily due to increasing proximal muscle weakness in the legs. Pseudohypertrophy of the calf muscles develops, which often leads to an erroneous diagnosis of Duchenne muscular dystrophy. The disease is benign and progresses very slowly. The hands are affected later. The facial muscles may be weakened, but the movements of the eyeballs are always full. Bulbar abnormalities are uncommon. Approximately half of the patients may develop bone deformities, and occasionally tendon retractions and contractures in the joints. Tendon reflexes from weakened muscles are absent or significantly suppressed. Fascicular tremor of the hands is often recorded.
Diagnostics.Identifying the genetic mutation is of primary importance. The concentration of CPK can exceed the upper limit of normal by 2-4 times. In half of the patients, EMG records spontaneous activity (fasciculations, fibrillations and positive sharp waves). With muscle tension, an increase in amplitude and polyphasia, an increase in duration and a decrease in the number of motor unit potentials are observed. Conduction along the sensory fibers of the nerves is always normal. The speed of conduction along motor fibers may decrease during a long course of the disease. SMA type III is differentiated from limb-girdle myodystrophies.
Kennedy's bulbospinal amyotrophy - a rare X-linked recessive form of SMA, debuting in the 4th decade of life; occasionally there are cases of the onset of symptoms at 12-15 years of age. The gene is mapped to the long arm of the X chromosome. The mutation affects the androgen receptor gene, including spinal motor neurons, making these
receptors insensitive to the influences of male sex hormones (androgens). The core of the clinical picture consists of weakness, atrophy and fasciculations in the proximal muscle groups of the limbs, tendon areflexia, facial weakness, atrophies and fasciculations in the tongue, perioral fasciculations, dysarthria and dysphagia, tremor and painful muscle spasms (cramps). Rarely, axonal neuropathy develops. Bulbar disorders usually appear 10 years after the onset of the disease. Endocrine disorders are typical: gynecomastia, testicular atrophy, decreased potency and libido, diabetes mellitus, infertility caused by azoospermia. The prognosis of the disease is generally favorable: the ability to walk and the ability to self-care are preserved. Life expectancy does not decrease, but the risk of malignant neoplasms due to hormonal imbalance (including breast cancer) is increased.
Diagnostics.Currently, it is possible to carry out direct DNA diagnostics, establish heterozygous carriage and carry out prenatal diagnostics. EMG reveals signs of denervation. CPK levels may be normal. The disease must be distinguished from amyotrophic lateral sclerosis.
6.4. Arthrogryposis multiplex congenita
Multiple congenital arthrogryposis is a syndrome, the main manifestation of which is limited mobility in the joints in combination with their deformities. Usually the distal joints (ankle, wrist) are affected, and less commonly the knee and elbow joints. Muscle weakness in arthrogryposis can be both neurogenic and myogenic in nature. The vast majority of cases are sporadic, the remaining cases are inherited in an autosomal recessive or X-linked manner. With neurogenic arthrogryposis, the most active phase of the disease is observed in the prenatal period and already in the newborn period breathing and swallowing are impaired; Some children die from aspiration. In milder cases, survival is higher and muscle weakness progresses very slowly or not at all. Respiratory disorders and feeding problems subsequently disappear. Contractures are present in both proximal and distal joints. Some newborns have concomitant micrognathia, high palate, facial anomalies, as in
Edwards syndrome (trisomy 18). Some children with neurogenic arthrogryposis have abnormal forebrain development. There are combinations with meningomyelocele, microcephaly and mental retardation. Myogenic arthrogryposis syndrome can be observed in myopathy with a disproportion of fiber types, congenital myodystrophies, myotonic dystrophy, myasthenic syndromes, and phosphofructokinase deficiency.
Diagnostics.Histological examination of muscles reveals characteristic signs of denervation and reinnervation. Manifestations of myopathy are also detected: an increase in the proportion of collagen fibers and adipose tissue, chaotic arrangement of medium-sized fibers, fibrosis of muscle spindle capsules.
6.5. Inflammatory myopathies
Dermatomyositis is a systemic immune-dependent angiopathy in which vascular occlusions and infarctions are observed, leading to the development of all the characteristic pathological changes in muscles, connective tissue, skin, gastrointestinal tract and nerve fibers. Pathogenesis is associated with the formation of antibodies and immune complexes and activation of the complement system. The perivascular infiltrate includes T-lymphocytes, which are overwhelmingly T-helper cells, B-lymphocytes and plasma cells.
Clinical picture. The peak incidence occurs at the age of 5-10 years, but cases of earlier onset (up to 4 months of age) have been described. Symptoms appear gradually or suddenly. The latent onset is characterized by fever, malaise and loss of appetite (anorexia). There may be no muscle weakness at this time. Such nonspecific symptoms persist for weeks or months, suggesting persistent infection. In most children, dermatitis appears before myositis. The rash is initially localized on the upper eyelids and looks like
erythema with foci of disturbed pigmentation and edema. It then spreads around the eyes and to the cheek area. Erythema and swelling on the extensor surfaces of the interphalangeal, elbow and knee joints develop later. Over time, the skin becomes atrophic and flaky. Myopathic changes include proximal weakness, muscle stiffness, and pain. Weakness increases, flexion contractures and joint deformities quickly develop. Tendon reflexes decrease and then disappear. In 60% of patients, calcifications are found in the subcutaneous tissue, especially under those areas of the skin where pigmentation is impaired. Multiple calcifications create an “armor” effect on radiography. In some children, the leading initial symptom is muscle rigidity, and skin and myopathic symptoms are not so pronounced. Gastrointestinal infarctions in the terminal stages of the disease have led to death in the past. Mortality from dermatomyositis has now decreased and is less than 5%, which is associated with improved treatment methods. More than 30% of adults with dermatomyositis are subsequently diagnosed with malignant neoplasms.
Diagnostics.The combination of fever, rash, myalgia, and weakness favors the diagnosis of dermatomyositis. At the onset of the disease, CPK levels are usually elevated. During active dermatomyositis, resting EMG reveals fibrillations and positive sharp waves; at muscle tension shortened low-amplitude polyphasic potentials are recorded. Muscle biopsy reveals myofiber atrophy. Capillary necrosis initially occurs along the periphery of the muscle bundle and causes ischemia of adjacent myofibrils. The most pronounced atrophy is in the bundles that come into contact with large fascial sheaths. Types I and II fibers (tonic and phasic) are affected equally.
Treatment.The inflammatory process is active for 2 years. Corticosteroids reduce its activity, helping to reduce symptoms. The best results are achieved when corticosteroids are prescribed early in the disease, in high doses, and used long-term. The drug of choice is prednisolone. Its initial dose is given at the rate of 2 mg/kg per day, but not higher than 100 mg/day. Body temperature often returns to normal within the first 48 hours from the start of therapy. Sometimes CPK levels return
to normal in the 2nd week of treatment in parallel with a noticeable increase in the strength of muscle contraction. In this case, further administration of prednisolone can be carried out according to a schedule every other day and in a dose that will reduce the severity of the side effects of steroid therapy. Prednisolone therapy is equally effective when taken daily or every other day, but only in cases where treatment is not interrupted. As muscle strength increases, the initial dose of prednisolone taken every other day can be reduced by 10% per month for 5 months. Further reduction in the dose of prednisolone is permissible by only 5% per month. When deciding whether to reduce the dose of corticosteroids, it is unacceptable to focus only on a decrease in CPK activity, since a noticeable increase in muscle strength occurs only 1-2 months after the enzyme level decreases, i.e. The leading criterion for reducing the dose of corticosteroids is positive clinical dynamics. In most patients, the maintenance dose of prednisolone taken every other day, which is necessary to normalize the strength of muscle contraction and CPK concentration, is 25% of the starting dose.
When treated with prednisolone, in some patients the rash completely disappears, but in most patients scarring of the skin remains. Long-term steroid therapy requires monitoring of gastrointestinal function. To protect the gastric mucosa, potassium chloride and H2 receptor blockers are prescribed. A serious complication of long-term therapy is the development of steroid myopathy, which can be regarded as an exacerbation of the underlying disease. It is quite difficult to distinguish developing steroid myopathy from exacerbation of dermatomyositis according to clinical criteria. With steroid myopathy, as a rule, the proximal parts of the extremities are affected, severe atrophy develops, and CPK activity does not increase. Most children with dermatomyositis improve after 3 months of treatment, but prednisone therapy must be continued for 2 years. If treatment is interrupted prematurely, relapses are inevitable, calcification and contractures develop. Drug treatment is complemented by physical rehabilitation; breathing exercises are necessary. Massage in the active phase is contraindicated. With proper treatment, a favorable outcome is observed in 80% of children with dermatomyositis. In case of resistance or intolerance to prednisolone
oral administration of cytostatics is indicated: methotrexate at a dose of 10 to 20 mg/m 2 body surface 2 times a week or azathioprine at a dose of 50-150 mg/day. During therapy, regular monitoring of liver function and blood cellular composition is necessary. The combination of corticosteroids and cytostatics avoids long-term therapy with high doses of prednisolone. In cases where the use of corticosteroids is limited by their side effects, plasmapheresis or a course of intravenous infusions of immunoglobulin are used. In the inactive stage, exacerbations usually do not occur.
Polymyositis. The etiology in most cases remains unknown. It is assumed that cellular and humoral mechanisms play a role in the pathogenesis, which is confirmed by the frequent development of the disease against the background of autoimmune processes (systemic lupus erythematosus, periarteritis nodosa, rheumatoid arthritis, scleroderma), as well as the good effect of the use of corticosteroids and immunosuppressants. Pathogenesis is associated with a cell-mediated cytotoxic reaction carried out by T lymphocytes sensitized to surface antigens of muscle fibers.
Clinical picture. Polymyositis usually occurs in adulthood (45-55 years), is rare in children and adolescents and is not associated with malignant neoplasms. Gradually, gradually, symmetrical proximal muscle weakness increases, fever and myalgia are atypical. Weakness of the neck flexors (“droopy head”) often develops. The disease is characterized by dysphagia and asthma attacks. Gradually, weakness spreads to the distal limbs. The severity of paresis varies, and in severe cases tetraplegia develops. Rarely, weakness is limited to distal muscle groups, the muscles of the eye or the face. The patient may experience periods of stabilization and even remission, which can lead to an erroneous diagnosis of limb-girdle myodystrophy. In the chronic course of the disease, muscle atrophy gradually increases; contractures may form. Tendon reflexes occur early in the disease and decrease as muscle mass decreases, but never completely disappear. This most important differential diagnostic feature allows us to exclude polyneuropathy. Sometimes the disease begins acutely with general malaise; severe muscle weakness develops over several days, pain appears in the muscles of the shoulder girdle. Muscle atrophy is very mild
or missing. Often, x-rays reveal calcifications in the muscles. In adults, cardiopulmonary complications are typical, which are not typical for the childhood form of the disease.
Diagnostics.Changes in CPK are rare. EMG studies almost always reveal typical signs of both myopathic and neurogenic processes. Muscle biopsy reveals various pathological abnormalities. Histologically, perivascular inflammatory infiltration is not always observed, so the absence of cellular infiltrates in biopsy specimens does not exclude the diagnosis of polymyositis.
For the treatment of polymyositis, the same regimen is used as for dermatomyositis. For patients who are resistant to corticosteroids, cytostatics (methotrexate) are indicated. Plasmapheresis and intravenous immunoglobulin are justified alternative treatment methods when conventional therapy is insufficiently effective.
Acute infectious myositis occurs after influenza or other respiratory viral infection. Symptoms of a viral infection last from 1 to 7 days, and then intense symmetrical pain and muscle weakness appear. In severe cases, the patient becomes immobilized within 1 day. Against the background of general weakness, proximal muscle groups are more severely affected than distal ones. Muscle palpation is painful. Tendon reflexes are preserved. CPK levels are usually more than 10 times the upper limit of normal. Almost immediately after the development of myositis, its spontaneous reverse development is observed. In the worst case scenario, the disappearance of pain requires 2 to 7 days of bed rest, after which the patient fully recovers.
Myotonia.The phenomenon of myotonia is a delayed reaction of muscle relaxation after contraction. There are action myotonia, percussion or mechanical myotonia and electromyographic myotonia.
In the pathogenesis of myotonia, instability of the muscle fiber membrane plays a role, which leads to repeated muscle contractions in response to a single stimulus. Repeated myotonic impulses do not occur spontaneously, but always under external influence or as a result of voluntary contraction. Action myotonia can be observed in a patient after intense muscle contraction. The patient is asked, for example, to squeeze his hand tightly
Rice. 6.14.Myotonic phenomena in a child with Thomsen's myotonia:
A- pseudohypertrophy of muscles; b- muscle roller with myatonic
reactions; V- inability to relax the hands during repeated movements
Rice. 6.15.
Rice. 6.16.Myotonic phenomena in a child with Thomsen's myotonia
fist and then quickly unclench it (Fig. 6.14-6.16). In this case, there is a certain time delay before the brush opens completely. When the same task is repeated, the myotonic phenomenon decreases each time and ultimately disappears. With congenital paramyotonia, the opposite phenomenon is observed - an increase in myotonia with repeated movements (paradoxical myotonia). Percussion myotonia is manifested by muscle contraction after mechanical stimulation (a quick and vigorous blow of a hammer to the muscle). This phenomenon can be observed in any muscle, but it is most striking when the thenar muscles are struck: there is a rapid flexion and adduction of the thumb that lasts several seconds. When large muscles are percussed, symptoms of “roller” and “row” occur; with transverse percussion of the tongue, a “constriction” or “pit” of the tongue is formed. Electromyographic myotonia is recorded when a needle is introduced into the muscle
Rice. 6.17.EMG for myotonia, “dive bomber hum”
Rice. 6.18.Thomsen's myotonia in a child. "Herculean muscles"
electrode. Active muscle tension or percussion causes the appearance of high-frequency repetitive discharges, which initially increase in frequency (from 100 to 150 Hz) and amplitude and then decrease. The total duration of such discharges is about 500 ms, and the sound equivalent resembles the roar of a dive bomber (Fig. 6.17).
The phenomenon of myotonia is the most important symptom of several heterogeneous hereditary diseases (Fig. 6.18, 6.19).
Myotonic dystrophy, or Rossolimo-Curshman-Steinert-Batten disease, is a multisystem disease that is inherited in an autosomal dominant manner with variable penetrance of the pathological gene. The etiology of the disease is associated with instability of the DNA region of chromosome 19, which is expressed in its pathological amplification (repetition). As a result, the number of copies of this gene increases from 50 to several thousand. Myotonic dystrophy can rightfully be classified as a class of so-called nucleotide triplet expansion diseases. The number of repeats increases in subsequent generations and correlates with a more severe course of the disease (anticipation phenomenon). Number of repetitions per child
Rice. 6.19.Thomsen's myotonia in an adult patient
Rice. 6.20.Rossolimo-Kurshman-Steinert-Batten myotonia. Typical appearance of a patient
when the disease is inherited from the mother, it increases to a much greater extent than when inherited from the father. A mother with 100 trinucleotide repeats has a greater than 90% risk of having a child with 400 repeats.
The disease is the most common type of adult-onset muscular dystrophy. The incidence of the disease is 3-5 cases per 100,000 population. Both sexes are affected with equal frequency. The first symptoms usually appear in teenagers. In advanced stages, myotonia, weakness of the facial muscles and distal limbs, cataracts, frontal baldness, and multiple endocrinopathy are noted. Atrophy of the facial muscles is so stereotypical in appearance that all patients look similar: the face is elongated and thin due to weakness of the temporal and masticatory muscles; the neck is thin (“swan”) due to atrophy of the sternocleidomastoid muscles; the eyelids and corners of the mouth are drooping, the lower half of the face sags, which makes the facial expression sad. Atrophy of the limbs is most pronounced in the distal parts: the forearms and peroneal muscles (Fig. 6.20, 6.21). There is dysphagia caused by damage to the muscles of the pharynx and smooth muscles of the esophagus. Tendon reflexes decrease and disappear.
In the later stages of the disease, atrophy of the small muscles of the hands develops. Patients complain of muscle tension and difficulty moving due to stiffness. Myotonia increases with cooling. In general, myotonic phenomena are not as pronounced as with congenital myotonia. A doctor can identify myotonic syndrome with questioning and confirm it with examination. For example, when shaking hands, a patient with myotonic dystrophy cannot immediately unclench the hand. Extraneural symptoms of myotonic dystrophy - cataracts, frontal alopecia or endocrine disorders - occur even before clinically significant symptoms of myotonia. Changes are often recorded on the ECG. In later stages, severe cardiomyopathy with transverse block, Adams-Stokes-Morgagni attacks, and heart failure may develop. Intestinal motility is disrupted and megacolon develops. Paresis of the diaphragm and intercostal muscles leads to hypoventilation and recurrent bronchopulmonary infections. Endocrine disorders include testicular atrophy, female infertility, hyperinsulinism, diabetes mellitus, adrenal atrophy, and impaired growth hormone secretion. Hypersomnia and obstructive sleep apnea, mental disorders up to severe dementia often develop.
Diagnosis is based on characteristic clinical manifestations and family history. EMG reveals myotonic phenomena, myopathic potentials, and minor signs of denervation. CPK activity is most often normal. There is no need for a muscle biopsy to confirm the diagnosis. DNA analysis reveals an increase in the number of trinucleotide repeats; it can be used to identify asymptomatic patients and perform prenatal diagnosis.
Treatment.Symptoms of myotonia are weakened by the administration of membrane stabilizer drugs: quinidine, procainamide, phenytoin
Rice. 6.21.Rossolimo-Kurshman-Steinert-Batten myotonia. “Swan” neck due to atrophy of the sternocleidomastoid muscle. Atrophy of the forearm extensor muscles, peroneal muscle groups, which leads to the appearance of a rooster gait
(diphenine) and carbamazepine (finlepsin). It must be taken into account that myotonia itself does not disable the patient and does not require constant drug therapy. Unfortunately, treatment for increasing muscle weakness is not yet effective. Patients often have a negative attitude towards treatment; do not tolerate anesthesia well, which can be complicated by the development of malignant hyperthermia.
Congenital myotonic dystrophy. A mother with myotonic dystrophy has a 1:4 chance of having a child with the congenital form of the disease, and 1:12 if the father is sick. The main signs of pathology in the intrauterine period in the congenital form are decreased fetal motor activity and polyhydramnios. 50% of children are born prematurely. Labor may be prolonged due to inadequate uterine contraction, and forceps may often be necessary. In some newborns, the function of the diaphragm and intercostal muscles is so severely affected that they are not capable of independent breathing at all. In the absence of immediate intubation and mechanical ventilation, many of them die immediately. The most noticeable clinical symptoms in newborns are: facial diplegia, in which the mouth is unusually pointed and the upper lip is shaped like an inverted V; generalized muscle hypotonia; joint deformities ranging from bilateral clubfoot to widespread arthrogryposis; dysfunction of the gastrointestinal tract in the form of paresis of the stomach muscles, swallowing disorders and aspiration. Weakness is most pronounced in the proximal limbs. There are no tendon reflexes. Myotonic phenomena are not caused by muscle percussion and may not be detected by EMG. Neonatal mortality reaches 16% and is often due to cardiomyopathy. In surviving children, muscle strength, as a rule, increases, and the processes of feeding and breathing are normalized during the 1st month of life.
The long-term prognosis is unfavorable: all children have mental retardation and severe clinical symptoms of myotonic dystrophy. Diagnosis requires a diagnosis of myotonic dystrophy in the mother, who usually has multiple clinical signs of the disease and myotonic EMG phenomena.
The diagnosis of the mother and child can be clarified after amplification of the DNA region of chromosome 19. Family members are at risk and subsequently undergo genetic testing to establish carrier status.
Emergency care for a newborn consists of immediate intubation and mechanical ventilation. The function of the gastrointestinal tract is normalized when cerucal (metoclopramide) is prescribed. Joint stiffness is reduced with the use of physical therapy and immobilization.
Congenital myotonia - a hereditary disease characterized by stiffness and true muscle hypertrophy. In 19% of families, autosomal dominant inheritance (Thomsen's disease) is traced, less often - autosomal recessive inheritance (Becker's disease). Most cases are sporadic. In general, patients with the autosomal recessive form have a later onset of the disease and present with more severe myotonic disorders than those with the autosomal dominant form. However, the symptoms of both forms are the same, so it is impossible to draw a conclusion about the type of inheritance solely based on clinical criteria (see Fig. 6.18, 6.19).
The pathological gene for both dominant and recessive forms of myotonia congenita is mapped to the long arm of chromosome 7, where the chloride ion channel gene is located.
The autosomal dominant form usually debuts in infancy with a change in voice when crying; the child begins to choke, and after crying the face very slowly relaxes. The disease is mild. In adulthood, myotonia can lead to generalized muscle hypertrophy (athleticism), but even in childhood, the muscles have the appearance of “Herculean muscles”. Sometimes the muscles of the tongue, face and masticatory muscles are involved. Muscle stiffness is not accompanied by pain; it increases when the patient is in the cold. Percussion myotonic symptoms are detected. Muscle mass, strength of contractions and tendon reflexes are normal. Immediately after rest, the muscles remain stiff and movements are difficult. However, after activation, stiffness disappears and normal range of motion is restored.
Diagnostics.The diagnosis is confirmed using an EMG study. The frequency of repeated muscle oscillations varies from 20 to 80 cycles per second from the moment the needle is initially inserted into the muscle until the onset of voluntary contraction. The amplitude and frequency of the potentials rise and fall, which is accompanied by a characteristic sound - “the hum of a dive bomber.” There are no signs of muscular dystrophy. CPK levels are normal. Muscle biopsy samples show hypertrophy of muscle fibers.
Treatment.Myotonia does not always require treatment, and medications are not effective enough. Sometimes you can reduce stiffness by prescribing phenytoin (Difenin) or carbamazepine (Finlepsin), which are given in moderate anticonvulsant doses. Novocainamide is prescribed at an initial dose of 200 mg 2 times a day, and then it is gradually increased to 400 mg 3 times a day. The drug reduces muscle stiffness in children with a recessive form of the disease. Diacarb (acetazolamide) is effective for some patients. In severe cases, a short course of corticosteroids is indicated. Calcium antagonists are useful (nifedipine 10-20 mg 3 times a day), as well as disopyramide 100-200 mg 3 times a day. It must be taken into account that succinylcholine, veroshpirone, potassium, antihyperlipidemic agents and β-blockers can enhance myotonic syndrome.
Myotonia relapsing (myotonia, aggravated by excess potassium) is an autosomal dominant syndrome associated with a mutation in the sodium channel gene. The gene is mapped to chromosome 17. Clinical manifestations are similar to myotonia congenita. The onset of muscle stiffness is usually observed after 10 years of age and can be provoked by general anesthesia. Myotonic phenomena are generalized, involving the trunk, limbs, and extraocular muscles. The severity of myotonia varies from day to day and decreases with warming. Worsening of the condition may occur after intensive physical activity or taking large amounts of potassium with food.
Diagnostics.EMG study reveals myotonic phenomena. There is no pathology in muscle biopsies. DNA analysis of the mutant gene encoding the α-subunit of the sodium channel is possible.
Treatment.Stiffness in relapsing-remitting myotonia can be prevented by mexiletine, a drug similar in structure to lidocaine; As with other channelopathies, diacarb (acetazolamide) may be effective.
6.6. Periodic paralysis
Periodic paralysis, or paroxysmal myoplegia, is a umbrella term for a group of channelopathies, rare hereditary diseases that are characterized by attacks of flaccid paralysis of skeletal muscles due to pathology of ion channels. Paralysis is divided depending on the level of potassium in the blood: hyperkalemic (Gamstorp disease), hypokalemic and normokalemic. In addition, periodic paralysis may
be primary (genetically determined) or secondary. Secondary hypokalemic periodic paralysis is caused by potassium loss in the urine or excess excretion from the gastrointestinal tract. Urinary potassium losses are associated with primary hyperaldosteronism, licorice intoxication, amphotericin B therapy, and some renal tubular defects. “Gastrointestinal” potassium losses are most often observed with severe chronic diarrhea, prolonged tube feeding and gastrofistula. Potassium is lost in adolescents with anorexia nervosa who abuse diuretics or vomit to “lose weight.” Hypokalemic periodic paralysis complicates thyrotoxicosis. Secondary hyperkalemic periodic paralysis may be due to renal or adrenal insufficiency.
Familial hyperkalemic paralysis inherited in an autosomal dominant manner with high penetrance. The mutation is located in the sodium channel gene.
Clinical picture. The onset of attacks of muscle weakness occurs in early childhood and even infancy. Attacks of weakness occur after intense physical activity. Before an attack, there are sensory disturbances - paresthesia in the face, upper and lower limbs, feeling of heaviness in the back. Occasionally, the patient can slow down the development of paralysis by walking or moving from place to place. In infants and young children, seizures are expressed by a sudden loss of muscle tone: they fall and cannot move. Older children and adults may experience both moderate attacks (lasting less than an hour and not leading to deep paralysis) and severe attacks (up to several hours). After several severe attacks, there may be some residual muscle weakness. Symptoms of myotonia in patients with hyperkalemic paralysis are moderate and may increase with cooling. Myotonia of the eyelids, tongue, muscles of the forearm and thumb is characteristic.
Diagnostics.During an attack, the potassium content in the blood usually exceeds 5 mmol/l. Oral intake of potassium chloride immediately after exercise immediately provokes an attack of weakness, during which the muscles do not respond to electrical stimuli.
Treatment.Acute attacks rarely require treatment because they are short-lived. In case of a full-blown attack, intravenous
new infusion of 40% glucose solution (up to 40 ml) or 10% calcium gluconate solution (up to 20 ml). Daily administration of Diacarb (acetazolamide) prevents recurrent attacks; the mechanism of preventive action of this drug in hyperkalemic and hypokalemic paralysis is unknown. You should avoid eating foods rich in potassium and increase the amount of carbohydrates and table salt in your daily diet.
Familial hypokalemic paralysis inherited in an autosomal dominant manner. The penetrance of the gene is reduced in women. The mutation is located on the long arm of chromosome 7, in the calcium channel gene. In 60% of patients, symptoms occur before 16 years of age, in the rest - up to 20 years of life. At first, attacks of weakness are infrequent, but then occur up to several times a week. Attacks are provoked by: rest after physical activity (attacks are often observed early morning), heavy intake of carbohydrate foods, excess salt in the diet, emotional stress, alcohol intake, hypothermia; in women - menstruation. Before and during the attack, the patient may experience thirst and oliguria, pain in the proximal muscle groups, then general weakness develops. Sometimes there is total paralysis, in which the patient is unable to even raise his head. Weakness of the facial muscles is rare; eye movements are always preserved. Respiratory failure does not develop. Most attacks last from 6 to 12 hours, and some last throughout the day (the so-called myoplegic status). Muscle strength is quickly restored, but after several severe attacks, fatigue, weight loss, especially of the proximal limbs, and suppression of tendon reflexes may occur. Autonomic disorders are typical: skin hyperemia, hyperhidrosis, lability of pulse and blood pressure. Outside of attacks of muscle weakness, patients have no symptoms of neuromuscular pathology.
Diagnostics.During an attack, the level of potassium in the blood may drop to 1.5 mmol/l, which corresponds to ECG changes: bradycardia, tooth flattening T, increasing intervals P-Q And Q-T. Muscles do not contract in response to electrical stimuli. For diagnostic purposes, an attack can be provoked by taking glucose at a dose of 2 g/kg and simultaneous subcutaneous administration of 10-20 units of insulin: an attack of paralysis develops after 2-3 hours.
Treatment.Acute attacks in patients with adequate renal function are treated with repeated doses of potassium in a dose of 5 to 10 g.
The same dose taken daily is recommended to prevent their occurrence. In younger children, the dose is lower. Taking diacarb (acetazolamide) daily has a beneficial effect, preventing attacks in many cases. It has low toxicity and is usually well tolerated even with long-term use. You should reduce the calorie content of your daily diet due to carbohydrates and reduce the amount of table salt. At the same time, foods rich in potassium are indicated: dried fruits, dried apricots, prunes, dairy products, potatoes.
Familial normokalemic paralysis. Some families have cases of autosomal dominant periodic paralysis with normal blood potassium levels. This is a variant of hyperkalemic periodic paralysis with a disturbance in the flow of potassium into the blood, when it is impossible to assess its true content in the tissues. Myoplegia lasts from several days to 2-3 weeks. The rate at which muscle weakness increases and decreases is usually slow. Tendon reflexes disappear during attacks. Some patients experience hypertrophy of individual muscle groups. Attacks are triggered by rest after intense physical activity, drinking alcohol, and cooling down. Taking potassium chloride can provoke an attack of paralysis, while consuming 8-10 g of table salt daily can avoid them.
6.7. Myasthenia gravis
Myasthenia gravis(myasthenia gravis)- an autoimmune neuromuscular disease, clinically characterized by pathological weakness and fatigue of voluntary muscles and associated with damage to acetylcholine receptors (ACh-R) of the postsynaptic membrane of striated muscles by specific complement-fixing antibodies (AT).
The prevalence of myasthenia gravis is 0.5-5 cases per 100,000 population in all populations. Children and adolescents under 17 years of age make up 9-15% of the number of patients with myasthenia gravis. Average age onset of the disease - 7.2 years. The onset of myasthenia gravis is possible at any age. Congenital forms have been described. Women get sick 3 times more often than men.
Etiology.A multifactorial disease in which specific value has a hereditary predisposition caused by an immunological defect and associated with anti-
histocompatibility genes B8 of the HLA system. Myasthenia gravis can be caused by a viral infection of the thymus gland, as a result of which it begins to produce T-lymphocytes with altered membrane structures; thymus tumor; in rare cases - primary brain damage of various etiologies.
The basis of the pathogenesis of myasthenia gravis is an autoimmune reaction to acetylcholinesterase receptors (ACh-R) of skeletal muscles. The level of antibodies to ACh-R in the blood of patients correlates with the severity of the disease. Antibodies to ACh-R block neuromuscular conduction because they destroy ACh, reduce the rate of its recovery, irreversibly changing the receptors of the postsynaptic membrane.
Pathological anatomy. Dystrophic changes occur in axon terminals, synaptic clefts and postsynaptic structures; immunoglobulins and complement are deposited in them. Moderate degenerative atrophy is observed in the muscles, less often fiber necrosis in combination with mild lymphoid infiltration and plasmorrhagia. In 70-90% of patients, pathology of the thymus gland is detected (hyperplasia of germinal follicles, lymphoepithelial thymomas). In rare cases, myocarditis, thyroiditis, and focal accumulations of lymphocytes in various organs are observed.
Clinical classification of myasthenia gravis (according to B.M. Hecht).
1. Degree of generalization of movement disorders:
1) generalized;
2) local:
a) ocular
b) bulbar,
c) skeletal.
2. Severity of movement disorders:
1) light;
2) average;
3) heavy.
3. The course of the myasthenic process:
1) remitting (myasthenic episodes);
2) non-progressive (myasthenic condition);
3) progressive;
4) malignant.
4. The degree of compensation for movement disorders under the influence of anticholinesterase drugs:
1) complete (up to restoration of functionality);
2) incomplete (the ability to self-service is restored);
3) bad (patients need outside care). Clinical picture. Myasthenia gravis is characterized by pathological
fatigue and weakness of striated muscles. Patients find it difficult to climb stairs, walk, stay in one position for a long time, or carry heavy objects.
The most often affected are the oculomotor, facial, and masticatory muscles, as well as the muscles of the pharynx, larynx, and tongue. Damage to the external muscles of the eye during the first examination is detected in 40-50% of patients, and as the disease develops - in 90-95%. Ptosis can be unilateral, occurring on one side or the other. In the morning and after rest, ptosis is less, increasing with general or visual stress, in the evening. During examination, increased ptosis can be provoked by asking the patient to close his eyes or sit down several times. Oculomotor disorders are asymmetrical, changeable under load, and do not correspond to the zones of innervation of the oculomotor nerves. Due to muscle weakness, nystagmus occurs in the extreme leads. Diplopia increases with visual and physical stress, bright light, in the afternoon (especially when watching TV), is more pronounced when looking into the distance, decreases after resting with eyes closed and in the morning (Fig. 6.22).
Weakness of the masticatory and temporal muscles leads to fatigue when chewing, sometimes to the point of drooping of the lower jaw; patients support their jaw while eating and help themselves when chewing with their hand. An important symptom is weakness of the facial muscles. It is more pronounced in the upper half of the face (in the orbicularis oculi muscles), and intensifies with repeated squinting and general physical activity. It is difficult for the patient to puff out his cheeks; a “transverse” smile occurs due to weakness of the orbicularis oris muscle. Weakness of the masticatory and temporal muscles is also noted.
Rice. 6.22.Weakness of the eye muscles in myasthenia gravis
Damage to the bulbar muscles (soft palate, pharynx and upper muscles of the esophagus), leading to dysphagia and dysarthria, develops in 40% of patients. It increases with speech, general physical activity, during eating and decreases after rest. Swallowing is impaired (the patient chokes when eating, liquid food gets into the nasal passages). Speech becomes nasal, and there may be hoarseness or modulation disturbances similar to stuttering. With severe dysarthria, the patient cannot swallow or speak.
Weakness of the muscles of the neck and trunk is more typical for elderly patients. Weakness of the back muscles is manifested by poor posture. Due to the weakness of the posterior group of neck muscles, difficulty arises when raising the head in a supine position or when extending the neck in a vertical position. If myasthenia gravis begins with weakness of the trunk muscles, bulbar and respiratory disorders subsequently develop.
Complaints of shortness of breath when inhaling are caused by weakness of the diaphragm or intercostal muscles. The weakening of the cough impulse leads to the accumulation of thick sputum, viscous saliva, which cannot be spat out or swallowed.
The muscles of the extremities, especially the proximal ones, neck, and torso are weakened. Upon examination, muscle atrophy, decreased muscle tone, and lability of tendon and periosteal reflexes are revealed. Weakness of the limb muscles can be isolated (without other symptoms of myasthenia gravis) or combined with weakness of other muscle groups. Weakness of the proximal extensor muscles is typical. The most commonly affected muscles are the deltoid muscle, triceps brachii muscle, and iliacus muscle.
In addition to movement disorders, myasthenia gravis is accompanied by various autonomic and endocrine disorders (hypo- and hyperthyroidism, hypocortisolism, etc.). Myasthenia gravis is characterized by the dynamism of muscle weakness during the day, its intensification after exercise, reversibility or reduction of weakness after rest. Deterioration of the condition is provoked by physical activity, negative emotions, menstruation, infections, increased ambient temperature, and improve night sleep, rest. A decrease in fatigue after the administration of anticholinesterase drugs (ACP) is pathognomonic.
The course of the disease is most often progressive, with remissions, or progressive without remissions. In a malignant course, bulbar and respiratory disorders develop during the first weeks of the disease. Myasthenia gravis often debuts after acute respiratory viral infection or
stress, one symptom (transient ptosis, bulbar paresis, etc.). The condition of patients with myasthenia gravis can be complicated by myasthenic crises or cholinergic crises.
Myasthenic crisis develops due to decompensation of myasthenia gravis or insufficient dosage of ACP; may be provoked by bronchopulmonary infection. In this case, there is a sharp deterioration in the condition with disruption of vital functions. Myasthenic crisis can be differentiated from other severe conditions accompanied by respiratory disorders by the presence of asymmetric external ophthalmoparesis, ptosis, bulbar syndrome, hypomimia, weakness of the muscles of the limbs and neck, which decrease in response to the administration of AChE drugs (Table 10).
Cholinergic crisis develops with an excessive dose of AChE drugs.
Table 10.Differential diagnosis of myasthenic and cholinergic crises
Mixed (myasthenic + cholinergic) crises occur in patients with myasthenia gravis due to improper use and/or an initially narrow range of therapeutic doses of ACEP, as well as against the background of conditions causing general or muscle weakness of various origins (intercurrent infections, somatic, hormonal disorders, taking drugs that affect the contractile function of voluntary muscles, and etc.).
The prognosis depends on the clinical form and treatment provided. Practical recovery is possible (in approximately 1/3 of patients), significant improvement, disability, and death, especially with thymoma. The main symptoms that threaten the patient's life are weakness of the laryngeal and respiratory muscles. Causes of death in myasthenia gravis: respiratory failure, aspiration pneumonia, side effects of corticosteroids and cytotoxic drugs.
Diagnostics includes anamnesis, clinical examination, test with AChE drugs (proserin, tensilone, kalimine), electromyography, immunological study, study of the thymus gland, morphological study of muscle biopsy, dynamic observation.
Clinical examination includes examination of general neurological status and assessment of the strength of voluntary muscles of the face, neck, trunk and limbs before and after exercise. Muscle strength is graded from 0 to 5 points, where 0 is no strength, 5 is normal strength, taking into account age and gender. Pathological muscle fatigue syndrome (an increase in symptoms after exercise) is also detected in the absence of symptoms of damage to the central nervous system.
Diagnostic criteria
1. Ptosis (unilateral, bilateral, asymmetrical, symmetrical): the appearance or intensification of ptosis after looking up for a long time or after quickly opening or closing the eyes repeatedly.
2. Weakness of masticatory muscles:
Insufficient resistance to forced closure of the lower jaw;
Palpation of the temporal muscles during chewing reveals their weak contraction;
Patients are unable to close their eyelids tightly or resist passive eye opening;
Patients cannot inflate their cheeks when pressing on them.
3. Weakness of the muscles of the larynx and palate is detected if:
The palate is inactive, the gag reflex is reduced or absent;
Difficulty swallowing liquid food.
4. Weakness of the tongue muscles is detected when the tongue presses on the doctor’s finger through the cheek.
5. With severe weakness of the neck muscles, the “head hangs down.”
6. Proserine test with assessment of muscle strength and fatigue is carried out before the subcutaneous administration of a 0.05% solution of proserine in a single age dosage and 30-40 minutes after it. The test is considered positive if muscle strength increases. There are:
A sharply positive test, when all myasthenic symptoms disappear;
Positive test - only individual symptoms remain;
A weakly positive test, which reduces the severity of myasthenic symptoms;
Doubtful proserine test - the severity of myasthenia gravis changes slightly;
Negative proserin test - clinical symptoms do not change after administration of proserin.
The presence of one of the first three variants of the proserine test is considered to confirm the diagnosis of myasthenia gravis.
EMG is performed on the most weakened muscles to identify the characteristics of neuromuscular transmission disorders (the abductor digiti minimi muscle in the digastric muscle of the floor of the mouth). The study is carried out against the background of discontinuation of ACEP during the day, immediately after physical activity and 2 minutes after exercise. Of great importance is the reversibility of EMG phenomena against the background of ACEP - an increase in the amplitude of the M-response. Electromyography shows a decrease in the amplitude of the second muscle action potential (normally both potentials are equal) in response to stimulation of the nerve with paired pulses with an interval of 0.1-0.7 s. In myasthenia gravis, a decrease in the amplitude of potentials with constant stimulation of the nerve is replaced by a plateau phase or an increase in amplitude, and in other diseases there is a steady decrease in the amplitude of the response. When recording the activity of individual muscle fibers, characteristic signs of damage to the neuromuscular synapses are often revealed. In 95% of cases, pathognomonic changes are detected on the EMG.
To exclude a tumor or hyperplasia of the thymus gland, which develops in 75% of patients with myasthenia gravis, computed tomography of the mediastinum and radionuclide scanning are performed.
An immunological study reveals the presence of antibodies to cholinergic receptors in 50% of patients with the ocular form of myasthenia gravis and in 80-90% of patients with the generalized form. In thymoma, antigens to skeletal muscles are also detected.
Immunological testing (ELISA, RIA) is a quantitative method for determining antibodies to AChR in the blood serum of patients with myasthenia gravis, which allows confirming the diagnosis with a probability of up to 80%.
Differential diagnosis is carried out with conditions whose leading symptom is muscle weakness:
Myasthenic syndromes (botulism, poisoning with aminoglycoside antibiotics, Itsenko-Cushing's disease, Addison's disease, hypo- and hyperthyroidism, poliomyositis);
Multiple sclerosis, neuroinfections (encephalitis, polyneuropathy,is): in patients, ophthalmoparesis is accompanied by hyporeflexia, ataxia, sensory disturbances, changes in CSF;
Amyotrophic lateral sclerosis: weakness is constant, atrophy, fasciculations, increased tendon reflexes, Babinski's symptom are noted;
Ocular form of myopathy: characterized by ptosis and symmetrical limitation of movements of the eyeballs; mild weakness of the muscles of the throat, neck, limbs and face;
Mitochondrial myopathies;
Neuroendocrine syndromes;
Other diseases of the central nervous system (tumors, vascular diseases of the brain and spinal cord): characterized by reflex disorders, conduction disorders;
Asthenoneurotic reactions, syndrome chronic fatigue and etc.
Treatment. General principles:
1. In the generalized form, the patient is hospitalized and physical activity is limited until anticholinesterase therapy is selected.
2. Drugs that block neuromuscular transmission and also have a depressant effect on the central nervous system are contraindicated.
and especially on the respiratory center (quinine, quinidine, propranolol, lidocaine, aminoglycosides, polymyxin, morphine, barbiturates, tranquilizers). 3. Treatment goals depend on the severity of the disease. Anticholinesterase drugs (ACDs)- drugs of choice for myasthenia gravis, inhibit the destruction of acetylcholine and promote its accumulation in the synaptic cleft, acting on cholinergic synapses, do not penetrate the BBB (Table 11). Side effects are caused by a simultaneous effect on autonomic cholinergic synapses and depend on the dose and tone of the VNS. These can be reduced by taking AChE inhibitors more frequently, but in smaller doses and with meals, which slows absorption. In some situations (menstruation, infections, remission), sensitivity to ACEP increases, and their dose is reduced. Patients are taught to adjust the dose independently. Relative contraindications to the use of ACEP are bronchial asthma, severe atherosclerosis, ischemic heart disease, and epilepsy.
Table 11.Anticholinergic drugs
Drugs | Time of action | Areas of use |
Prozerin (neostigmine) | Onset of action after 20-40 minutes, duration 2-4 hours | Used primarily for drug testing and in acute conditions |
Kalimin 60 N, Kalimin-forte (pyridostigmine bromide) | Starts in 45 minutes, works 4-8 hours The interval between doses is 5-5.5 hours. | It is most widely used, well tolerated, and effective in all forms, including bulbar. Kalimin forte (parenteral) - for violation of vital functions and persistent bulbar palsy. When transferring patients to parenteral administration of drugs, it is taken into account that 1 tablet of kalimine (60 mg) is equivalent to 1 ml of 0.05% solution of proserin |
Auxiliary therapy: potassium preparations (prolong the effect of ACEP); a diet rich in potassium (baked potatoes, dried apricots, bananas, etc.); potassium-sparing drugs (veroshpiron); potassium chloride 3.0 g/day in solutions, powders, tablets to prevent an overdose of ACEP; calcium preparations; tonics (extracts of Eleutherococcus, Rhodiola, Leuzea, pantocrine); multivitamins, aminophylline (a phosphodiesterase blocker that increases the content of cAMP in the presynaptic membrane), anabolics (riboxin, retabolil).
Pathogenetic therapy - thymectomy. Efficiency is 70-90%, remissions are possible. Indications for surgical treatment are:
a) malignant forms of myasthenia;
b) progressive form of myasthenia;
c) myasthenic condition, depending on the severity of the defect.
Contraindications to thymectomy:
a) severe decompensated somatic diseases;
b) old age.
Preoperative preparation includes restorative therapy, plasmapheresis, glucocorticoids if indicated, radiation therapy (contraindicated in children and adolescents).
Glucocorticoids (prednisolone, dexamethasone) indicated when other methods are ineffective. They are prescribed daily or every other day, 60-150 mg/day (1-1.5 mg/kg/day) in the morning, immediately after breakfast, every other day; in case of severe exacerbation, daily (until compensation of vital disturbances), after 5-7 days (until the therapeutic effect) switch to the every other day regimen. Maintenance dose - every other day 20-30 mg per day, taken for several months. In approximately 75% of patients, corticosteroid therapy leads to significant improvement. After stable improvement, the dose of corticosteroids is slowly (over several months) reduced to maintenance (5-15 mg daily or 10-30 mg every other day). Sometimes it is possible to completely stop corticosteroids. To avoid initial deterioration, treatment can be started with low doses (25 mg of prednisolone every other day) with a gradual increase in the dose by 12.5 mg every third dose until the daily dose reaches 100 mg or a good effect is obtained. Improvement is noted after 6-7 weeks of treatment. In these cases, the dose begins to be reduced no earlier than 3 months after the first dose.
Plasmapheresisprescribed for exacerbations, myasthenic crises, preoperative preparation, ineffectiveness of corticosteroid therapy. 3-5 sessions are carried out every other day, then 2-3 times a week. Plasmapheresis is carried out with plasma replacement or the use of substitute proteins. Hemosorption and enterosorption are carried out in patients with a generalized form of myasthenia gravis in order to remove antibodies, and in mixed crises and ineffectiveness of massive drug therapy - for the purpose of detoxification.
Cytostatics (azathioprine, cyclophosphamide and cyclosporine) prescribed under the control of blood tests. Immunoglobulin G preparations (iv 0.4 g/kg/day daily for 5 days; or 3-5 g per course) are effective for intercurrent infections, during myasthenic or mixed crisis.
Treatment of crisesaimed at compensating vital disorders, stopping exacerbations and eliminating metabolic disorders. When treating myasthenic crisis, ACEP is administered parenterally (Kalimin-Forte 1-1.5 ml IV or IM every 4-5 hours or Proserin 1.5-2 ml every 3 hours). Mechanical ventilation with the complete abolition of ACEP, the prescription of immunosuppressive therapy against the background of antibacterial drugs is carried out to prevent intercurrent infections. Disconnection from the device is carried out only after 30 minutes of spontaneous breathing, with compensation of respiratory disorders and against the background of Kalimina-Forte for 5-6 hours. Large doses of glucocorticoids are prescribed according to an alternating scheme (pulse therapy - 1000-2000 mg IV drip every other day) followed by transfer to oral approx. They also stabilize cardiopulmonary activity. Plasmapheresis and intravenous infusions of normal human immunoglobulin are performed. Cholinergic crisis is stopped with atropine, cholinesterase reactivators (dipiroxime); detoxification is used.
In addition to painful disorders resulting from injuries (for example, tears and sprains), muscle disorders can also occur in the absence of external factors impact. Muscle diseases include:
Muscle cramp;
Rheumatic diseases;
Inflammation;
Genetic diseases;
Metabolic disease;
Changes in muscle cells.
Let's look at the whole disease in more detail.
Muscle cramp
A cramp may occur as a result of dehydration (exicosis). At this point the muscles contract and become hard, then they slowly relax. The cramp may occur at night or in the morning. The person suddenly begins to feel severe pain in the muscle. Seizures are most common in older people. When too much stress is put on the muscles or their nutrition is disrupted, hardening occurs. The muscle fibers transform into muscle tissue, in which hard areas in the form of nodes are felt. In such cases, it is necessary to drink a lot of fluids in order to restore the water-salt balance in the body. Massage also comes to the rescue. If muscle pain does not stop, then you need to see a doctor. Hardening is treated with massage, vitamin E and warm baths.
Rheumatic diseases
There are a very large number of diseases that can be classified as rheumatic. In these diseases, the source of damage is the muscle itself, or the blood vessels that feed the muscle. Pain appears in the hips and shoulders. Some rheumatic diseases (for example, dermatomyositis) affect the muscles. In this case, treatment with hormones – glucocorticoids – is necessary. They suppress inflammation but cause side effects. Therefore, they try to suppress rheumatic diseases with the help of anti-inflammatory drugs or physiotherapy.
Hormonal imbalance
Painful muscle weakness in medicine is referred to as endocrine myopathy, which appears due to increased function of the thyroid gland or adrenal glands. After treatment, the pain disappears.
Muscle inflammation
Inflammation of the muscles is called myositis. Symptoms of this disease the same as with rheumatism, but the distinguishing feature is inflammation of the muscles themselves. Myositis is characterized by pain and severe muscle weakness. Muscle inflammation is treated in the same way as rheumatic diseases.
Lack of minerals
Muscles require certain substances to function properly. Potassium deficiency causes paralysis. This is especially felt by young people and children in the morning after a difficult last day. Treat with drugs containing potassium. In addition, you should not eat much or exercise actively before going to bed.
Enzyme deficiency
Children may rarely have an enzyme deficiency. Often there are dysfunctions of enzymes that take part in the breakdown of glucose and glycogen, which are a source of energy for muscles. As a result of congenital deficiency of the enzyme, the muscles receive little energy due to weakening of their work. A person with this diagnosis should avoid physical activity.
Painful muscle fatigue
Muscle fatigue, which is accompanied by pain, occurs due to acidosis. To obtain energy under heavy loads, glucose is broken down into lactic acid, which is difficult to remove from the body. Accumulating in the muscles, lactic acid causes pain.
All over the world, athletes drink mangosteen juice to prevent muscle pain, improve nutrition, recovery and treatment.
It is necessary to drink clean water.
Muscles(musculi; synonym for muscles). Functionally, involuntary and voluntary muscles are distinguished. Involuntary muscles are formed by smooth (non-striated) muscle tissue. It forms the muscular membranes of hollow organs, the walls of blood and lymph vessels. The structural unit of smooth muscle tissue is the myocyte, in the cytoplasm of which there are thin fibers - myofibrils. Smooth muscle tissue ensures peristalsis of hollow organs, tone of blood and lymphatic vessels.
Voluntary muscles are formed by striated (striated) muscle tissue, which constitutes the active part of the locomotor system and ensures movement of the body in space. A special place is occupied by the myocardium, which consists of striated muscle tissue, but contracts involuntarily (see. Heart ). The structural and functional unit of skeletal muscle tissue is the striated muscle fiber, which is a multinuclear symplastic formation ( rice. 1 ). The length of muscle fibers ranges from a few millimeters to 10-12 cm, diameter - from 12 to 100 µm. A muscle fiber has a cytoplasm called sarcoplasm; it is surrounded on the outside by a thin membrane - the sarcolemma. The specific contractile apparatus of muscle fibers is made up of myofibrils. The transverse striation of a muscle fiber is determined by the special structure of myofibrils, in which areas with different physicochemical and optical properties alternate - the so-called anisotropic and isotropic discs. The different optical properties of these discs are due to the different combinations of thin and thick myofilaments in them - the thinnest protein filaments that make up the myofibrils. Thin myofilaments are built from the protein actin, and thick ones are made from myosin. When these proteins interact, the myofibril shortens, and, as a consequence of this process, which occurs synchronously in almost all myofibrils, muscle fiber contraction occurs.
Muscle fibers contain a specific protein, myoglobin, which accumulates oxygen supplied to the muscles during respiration and releases it as needed during muscle contraction.
Muscle fibers are combined into bundles of various orders. The loose connective tissue inside the muscle bundles is called endomysium. The bundles of muscle fibers are connected to each other by loose fibrous connective tissue - the internal perimysium. On the outside, the muscles are covered with denser connective tissue—the external perimysium.
In places of attachment of skeletal M. to the bones, they often turn into tendons, especially well expressed in long M. All tendons are built from dense connective tissue and are distinguished by high tensile strength. Muscle fibers are connected to tendons through collagen fibers, and endomysial and perimysial fibers are directly woven into the tendon tissue.
dislocations) using a standard protractor. Muscle strength is determined using a Coplen dynamometer, as well as during active movements in the joint with resistance provided by the examiner’s hand. Electromyography allows you to more objectively judge the functional state of the muscles.Pathology
Pathology includes malformations, damage, inflammatory and dystrophic changes, tumors.
Developmental defects muscles are found in almost all areas of the body, but are more often observed on the upper extremities. M.'s anomalies can be divided into three groups: 1) complete absence of individual muscles; 2) the appearance of additional muscles; 3) various changes in shape, including the absence or underdevelopment of any part of the muscle or the presence of additional tendons and heads, splitting of the muscle, etc. More common is congenital underdevelopment of the sternocleidomastoid muscle, leading to torticollis, as well as a defect in the development of the diaphragm, which leads to the formation of diaphragmatic hernias (see. Diaphragm ). Treatment of these defects is usually surgical.
Damage divided into closed and open. Closed injuries of M. include bruises, complete and incomplete ruptures of muscles and their tendons, the formation of muscle hernias. In case of bruise and partial rupture in the thickness of M., a painful compaction without clear boundaries is determined. As a result of damage to small blood vessels, subcutaneous and intermuscular pain develops, the contractility of the muscle is impaired. As swelling increases, contraction and shortening of the muscle occurs. Active movements become sharply painful, which leads to painful contracture, or antalgic posture; passive movements are preserved. The outcome of an extensive intermuscular hematoma can be scar replacement, or ossification of the damaged area of the muscle. Closed (subcutaneous) ruptures of the muscle occur with sudden muscle tension and in some cases with direct trauma. The rupture most often occurs at the junction of the muscle into the tendon, which is caused by degenerative processes. At the time of injury, patients feel a sudden click, accompanied by sharp pain and loss of active movements. In cases of complete rupture of the muscle, it is possible to determine retraction at the site of damage and bulging of the contracted edges of the muscle.
Dystrophic diseases muscle tissue are progressive and often hereditary (see. Myopathies, Myasthenia gravis, Myatonia ) or autoimmune ( dermatomyositis etc.) nature.
Tumors can occur in any organ where there are muscle elements. They develop from both striated and smooth muscles. They can be benign and malignant.
Benign tumors. Leiomyoma occurs more often in people aged 30-50 years. It is found in all organs where there are smooth muscle fibers (in the uterus, gastrointestinal tract, bladder, prostate gland, skin, etc.). Leiomyomas have a round shape, a dense elastic consistency, and are clearly demarcated from the surrounding tissues. Leiomyomas are often multiple.
Leiomyomas of the skin - see. Leather, tumors. Rhabdomyoma is observed more often in children. Usually located deep in the muscles and in the area of large joints. The tumor is a node, sometimes reaching 10-15 cm in diameter, densely elastic consistency, mobile and well delimited from surrounding tissues, has a pronounced capsule. It grows slowly.
The diagnosis of benign tumors of muscle tissue is established on the basis of clinical data, the results of morphological and additional research methods - ultrasound and computed tomography, angiography. Due to the poor clinical picture, it is difficult to differentiate benign and malignant tumors. Rhabdomyomas of the extremities are differentiated from myogenic myomas and synoviomas. Fibroids emanating from the walls of internal organs - with other neoplasms of these organs.
Treatment is surgical. Radical excision of the tumor provides a cure. For skin leiomyomas, electroexcision or cryodestruction can be used. The prognosis is favorable.
Malignant tumors. Leiomyosarcoma is localized, like leiomyoma, most often in the uterus, less often in the gastrointestinal tract and bladder. It is rare in soft tissues of the extremities and trunk. Accounts for 4% of all soft tissue sarcomas. The tumor has the shape of a node of soft elastic consistency and can reach 15-20 cm in diameter. It is extremely malignant. Multiple early metastases to the lungs are characteristic. Metastases in regional lymph nodes are found in approximately 2% of patients.
Rhabdomyosarcomas are relatively rare - they account for 4.1%, ranking fifth among malignant soft tissue tumors. They are observed mainly in adulthood and old age, in men - 2 times more often than in women. They are localized mainly on the extremities, in the head and neck area, and in the pelvis. Polymorphic rhabdomyosarcoma occurs mainly in elderly people and is localized on the extremities; alveolar rhabdomyosarcoma - in adolescents and young adults,
found in any part of the body; embryonal rhabdomyosarcoma - in newborns and young children, its typical localization is in the pelvic area. Rhabdomyosarcomas can develop outside of connection with muscle tissue (in the retroperitoneal tissue, mediastinum, nasopharynx, etc.). The main symptom of rhabdomyosarcoma is the presence of a single (sometimes multiple) fast-growing node in the thickness of the muscles. As a rule, there is no pain or dysfunction of the limb. The neoplasm is prone to skin germination and ulceration. Characteristic is early hematogenous metastasis to the lungs. Metastases in regional lymph nodes occur in 6-8% of cases. In the early stages, diagnosis is difficult. To correctly interpret the nature of the lesion, one should take into account the typical localization in the thickness of the muscles, the rapid growth of the tumor, skin lesions and ulceration. The final diagnosis is established using ultrasound and computed tomography, angiography.Surgical treatment is wide excision of the tumor. If the tumor recurs on the extremities, amputation (disarticulation) is indicated. Radiation therapy is used for palliative purposes in case of unremovable tumors or in the postoperative period. Rhabdomyosarcomas are usually resistant to radiation. Chemotherapy is used to treat disseminated forms and is included in the combination therapy plan for the primary tumor. The most active drug is the antitumor antibiotic adriamycin. The prognosis is unfavorable.
Operations
Operations on the myocardium are performed to remove a pathological focus, tumor, open a hematoma, empty the hematoma, or to stitch a rupture, plastic surgery for contracture, etc. Crossing the muscle - myotomy or its complete removal is used to eliminate contractures caused by irreversible shortening of the muscle, in in cases where tenotomy cannot be performed. In some cases, muscle is used as a plastic material to close tissue defects, for example, to fill bone cavities in osteomyelitis, etc.
For suturing the M., as a rule, absorbable suture material. Sutures are placed on the M. without much tension, so as not to cause disruption of their nutrition (see. Surgical sutures ).
Bibliography: Human Anatomy, ed. M.R. Sapina, vol. 1, p. 162, M., 1986; Daniel-Beck K.V. and Kolobyakov A.A. Malignant tumors of the skin and soft tissues, M., 1979, bibliogr.; Clinical Oncology, ed. N.N. Blokhin and B.E. Peterson, vol. 1. p. 385, M., 1979; Kovanov V.V. and Travin A.A. Surgical anatomy of human limbs, M., 1983: Movshovich I.A. Operative Orthopedics, M., 1983, Guide to the pathoanatomical diagnosis of human tumors, ed. ON THE. Kraevsky et al., p. 43, M., 1982; Trubnikova F. Traumatology and Orthopedics, Kyiv, 1986; Ham A. and Cormack L. Histology, trans. from English, vol. 3, p. 241, M., 1983.
Neuromuscular diseases are a group of hereditary and non-hereditary diseases characterized by dysfunction:
- muscular system - myopathy and myotonia;
- neuromuscular synaptic apparatus - myasthenia gravis and myasthenic syndromes;
- peripheral nerves, motor neurons of the anterior spinal horns - secondary (neurogenic) amyotrophies (neural and spinal).
The group of neuromuscular diseases includes disorders of locomotor function and muscle weakness. The following neuromuscular diseases are distinguished:
- myopathies;
- myotonia;
- secondary (neurogenic) amyotrophies;
- myasthenia gravis.
Diagnosis and differential diagnosis of NMD, especially in the early stages of its course, is very difficult. In such cases, genetic, neurophysiological, biochemical and morphological research methods become of great importance.
Neurophysiological research methods:
- electromyography (EMG);
- electroneuromyography (ENMG).
Local (needle) EMG it is especially informative in primary muscle processes and registration of denervation potentials (one-, two-phase potentials of fibrillation, fasciculations).
Global (cutaneous) EMG informative for neural and spinal levels of damage (type II EMG according to Yusevich), as well as for studying the functional state of peripheral motor neurons and the influence of the structures of the pyramidal and extrapyramidal systems on them.
ENMG allows you to determine the speed of the impulse in the afferent and efferent fibers of peripheral nerves. Analysis of evoked muscle responses and nerve action potential (AP) is informative in the diagnosis of myelinopathy (neurosensory and/or neuromotor) and axonopathy (neurosensory and/or neuromotor). Stimulation ENMG (rhythmic nerve stimulation method) identifies lesions in neuromuscular (synaptic) transmission.
Neurophysiological studies make it possible to judge the localization of the pathological process and the degree of involvement of the neuromotor apparatus, and also help to differentiate various neuromuscular diseases. These methods are non-invasive and can be used repeatedly.
Biochemical research involve determining the activity of enzymes, in particular creatine phosphokinase (CPK), lactate dehydrogenase (LDH) and fructose diphosphate aldolase (FDA), as well as changes in the creatine-creatinine index. The activity of these enzymes increases sharply with progressive muscular dystrophy (PMD), especially in the early stages of the process: CPK activity in the blood serum increases tens of times, sometimes 50 times or more; LDH activity - 5-7 times; FDA activity - 2-5 times. In later stages, the activity of serum enzymes decreases to normal values. With secondary neural and spinal amyotrophies, the properties of enzymes change relatively little. CPK activity is a very sensitive marker of muscle damage, but its moderate increase is also observed in amyotrophic lateral sclerosis, after exercise or a convulsive attack.
Pathohistological studies. Based on the results of skeletal muscle biopsy in patients with PMD, the proliferation of connective tissue is determined; in spinal and neural amyotrophies, denervation atrophy of muscle fibers is determined.
Treatment of neuromuscular diseases
Treatment of NMD, including PMD, is extremely difficult. Difficulties in therapy are associated with the sometimes impossible determination of the primary metabolic defect in certain forms of hereditary diseases, as well as with the steadily progressive course of these diseases, especially primary PMD.
Treatment is aimed at slowing the rate of development of the disease and maximizing the patient’s ability to self-care. Treatment principles:
- correction of skeletal muscle metabolism (metabolism stimulants, anabolic steroids, potassium supplements, vitamins);
- stimulation of the segmental apparatus (myostimulation, neurostimulation, biofeedback - EMG biofeedback methods, reflexology, balneotherapy,
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