Muscle weakness

Muscle weakness is a lack of contractile ability of muscles.

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Causes muscle weakness

Pathological conditions manifested by muscle pain or muscle weakness may be the result of a wide range of different neuromuscular diseases. The cause of muscle weakness may be either direct damage to muscle tissue or to the nervous system or neuromuscular synapse, so the issue of differential diagnosis in such patients is particularly acute.

Primary muscular diseases

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Amyloidosis

The onset of the disease can be at 30-50 years, the course is chronic, progressive. It is characterized by damage to the striated and smooth muscles (there may be paralysis of the eye muscles, macroglossia, amyotrophy, lack of tendon reflexes, impotence), blood vessels, skin, mucous membranes, peripheral nerves, and clouding of the vitreous body. Macroscopically, the muscle looks pale and hard. When determining the activity of CPK, no deviations from the norm are found. Morphological examination of skeletal muscles reveals diffuse or focal deposits of amyloid in the perimysium, atrophy of muscle fibers.

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Myositis

Granulomatous myositis may occur with sarcoidosis, Crohn's disease, viral and parasitic infections. Acute and chronic forms are distinguished. In some cases, palpable nodules form in the muscles of the upper and lower extremities. Clinically pronounced muscle weakness is observed in 0.5% of cases. The disease progresses slowly: changes in the muscles of the proximal extremities (amyotrophy, sometimes pseudohypertrophy) are most often observed; damage to the long muscles of the back (development of hyperlordosis) and peripheral nerves is typical. Cases of skin syndrome resembling dermatomyositis have been described. General urine analysis shows hypercalciuria. CPK activity may be normal. Morphological examination of skeletal muscle biopsy reveals epithelioid cell sarcoid granulomas.

Dermatomyositis; polymyositis; juvenile dermatomyositis; myositis associated with CTD (overlap syndromes), in malignant tumors, with "inclusions".

Infectious myositis; bacterial infections (pyomyositis, tuberculous myositis), protozoal infection (toxoplasmosis, sarcosporidiosis), helminthiasis (trichinellosis, cysticercosis, echinococcosis), viral myositis (influenza A or B, parainfluenza, adenovirus, cytomegalovirus, Varicella zoster, measles, Epstein-Barr virus, Coxsackie, HIV) - increased CPK activity is possible.

Viral myositis occurs with various symptoms; slight short-term to pronounced diffuse myalgia (with swelling, pain on palpation). Rhabdomyolysis may develop. Muscle damage in echovirus infection may resemble typical dermatomyositis.

Infectious diseases

• Toxoplasmosis - fever, lymphadenopathy, hepatosplenomegaly are possible. Muscle weakness may mimic polymyositis, eosinophilia in the general blood test is not a constant symptom.
• Trichinellosis. Muscle weakness peaks at 3 weeks. Myalgia and muscle weakness may be diffuse or local, pain is noted on muscle palpation. Sometimes observed: periorbital edema; muscle damage of the proximal limbs and back, diaphragm, esophagus, intercostal and external eye muscles (ptosis). Often - skin manifestations similar to those in dermatomyositis. In the general blood test - eosinophilia (up to 60%).
• Cysticercosis. Muscle damage is often asymptomatic, but pseudohypertrophy and muscle weakness may occur. As a rule, the pelvic girdle muscles are not treated during the process. When palpating the muscles, significant pain and subcutaneous compaction are noted. Characteristic: fever, CNS damage, eosinophilia in the general blood test.
• Echinococcosis. Most common localization: muscles of the back, pelvic and shoulder girdle. Usually one area is affected (tumor-like compaction associated with surrounding tissues, moderate pain when moving). There is a risk of rupture of the echinococcal cyst.

Drug and toxic myopathies

Due to the use of glucocorticosteroids, penicillamine, delagyl, plaquenil, colchicine, statins, long-term therapy with high doses of thyroid hormones, etc.: alcohol, drug (cocaine) intoxication. The severity of clinical manifestations depends on the severity of toxic damage (from minimal myalgia and weakness to the development of rhabdomyolysis). Normal or increased activity of CPK is noted.

Alcoholic myopathy can be acute (from myalgia to rhabdomyolysis) and chronic (proximal muscle weakness, amyotrophy - atrophy of type 2 fibers). CPK activity is within normal limits.

Glucocorticoid myopathy - predominantly affects the muscles of the shoulder and pelvic girdle, there may be myalgia.

Penicillamine, plaquenil, delagyl. Development of proximal muscle weakness has been described with their use.

Statins. Severe rhabdomyolysis has been reported with their use.

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Metabolic myopathies

Disturbance of muscle glycogen and lipid metabolism. At rest, patients are not bothered by anything. The main clinical manifestation is decreased tolerance to physical activity: fatigue and muscle weakness in the proximal parts of the limbs are noted several minutes after the onset of intense physical activity, there may be painful myogenic contractures, cramps. In laboratory studies: myoglobinuria may be present, CPK activity is normal, with physical activity - there may be growth.

Mitochondrial myopathies

Kearns-Sayre syndrome, LHON syndrome (Leber), MERRF, MELAS, NARP, MMS syndromes. The clinical picture is varied. In laboratory studies, CPK activity may be elevated. In a striated muscle biopsy, there are "torn" red muscle fibers, a large number of mitochondria in myofibrils, replacement of muscle tissue with fatty or connective tissue, shortening and thinning of muscle fibers, and in immunohistochemical studies, there is an increase in the content of oxidative enzymes.

• LHON syndrome. More than 70% of patients are men. Its onset is possible at 8-60 years of age, more often in the third decade of life. The course is often acute - atrophy of the optic nerve.
• MELAS syndrome: progradient type of myopathy: encephalomyopathy, lactic acidosis, stroke-like attacks, possibly growth hormone deficiency and diabetes mellitus.
• MERRF syndrome: myoclonus epilepsy, cerebellar ataxia, muscle weakness, less commonly sensorineural deafness, peripheral polyneuropathy, optic nerve atrophy, spastic hemi- or tetraplegia, dementia.
• NARP syndrome. Onset is possible from infancy to the second decade of life: developmental delay, muscle weakness, ataxia, pigmentary degeneration of the retina.
• MMS syndrome: infantilism, cardiomyopathy, mental retardation, generalized tonic-clonic seizures: glomerulosclerosis.
• Kearns-Sayre syndrome: cerebellar syndrome, cardiac conduction system blocks, retinal pigment degeneration.

Electrolyte imbalance

Decreased concentration of potassium, calcium, magnesium, sodium, phosphorus ions in the blood. Characteristic symptoms include malaise, muscle weakness, myalgia, hyperesthesia, impaired deep sensitivity, fasciculations, convulsive syndrome, etc.

Non-progressive muscular dystrophies

Nemaline myopathy, central core disease, myotubular myopathy are benign, they are detected at 40-50 years of age, characterized by mild diffuse or proximal muscle weakness, there may be dysplastic changes in the skeleton. Sometimes by puberty, regression of symptoms is noted, involvement of the oculomotor muscles in the pathological process is possible, moderate bilateral ptosis, there may be bone deformations. Patients usually retain their ability to work. When determining the activity of CPK, a slight increase in the indicator is noted.

Progressive muscular dystrophies

Including Aran-Duchenne amyotrophy, Becker myopathy, Landouzy-Dejerine, Rottauf-Mortier-Beyer, Erb-Roth muscular dystrophy, etc. Clinical manifestations: "ascending" type of lesion (first - muscles of the lower extremities, then - the upper): hypotrophy of the muscles of the thighs and pelvic floor, then - the shoulder girdle; "winged scapulae"; pseudohypertrophy of the muscles of the lower legs, "duck gait", increased lumbar lordosis.

At the onset of the disease, an increase in CPK activity is noted, in advanced cases the value is normal. Morphological picture: pronounced atrophy and hypertrophy of muscle fibers, at the onset of the disease there may be necrosis and an inflammatory reaction.

Endocrine myopathies

May occur with Addison's disease, hypercorticism, thyrotoxicosis, hypothyroidism (most often), acromegaly, hyperparathyroidism. Laboratory tests show normal or increased (e.g., with hypothyroidism) CPK activity.

• Acromegaly: muscle weakness; rapid fatigability; pseudohypertrophy and later - muscle hypotrophy; often - painful cramps.
• Addison's disease: generalized muscle weakness; cramps; rapid fatigability and prolonged recovery period after physical exertion; hyponatremia; flaccid hyperkalemic tetraparesis; hyperpigmentation of the skin.
• Hypercorticism: damage to the muscles of the pelvic and shoulder girdle; gradual development of muscle weakness.
• Hyperparathyroidism: muscle weakness in the proximal extremities, cramps.
• Hypothyroidism: 40% of patients experience muscle weakness in the proximal extremities, easy fatigue, myalgia, and sometimes dysarthria.
• Thyrotoxicosis: muscle weakness and hypotrophy; convulsions; myalgia; acute thyrotoxic myopathy - rapid increase in weakness, oculomotor disorders, weakness of the masticatory muscles, muscles of the pharynx, tongue.

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Neurogenic diseases

Peroneal muscular atrophy (Charcot-Marie-Tooth disease)

The onset of the disease is in childhood or adolescence (symmetrical lesions are not always observed): amyotrophy of the distal lower extremities (peroneal group), formation of a high arch of the foot, later involvement of the muscles of the distal upper extremities in the process, sensory disturbances of the "glove" and "sock" type, fasciculations are possible, reduction or disappearance of reflexes.

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Amyotrophic lateral sclerosis

Patients are found to have asymmetric atrophy and weakness of the muscles of the distal parts of the arms, then the muscles of the shoulder and pelvic girdle, fasciculations, hypertonia, hyperreflexia, pathological reflexes, bulbar disorders (speech disorder, swallowing, respiratory failure). When determining the activity of CPK, an increase in the indicator is sometimes noted.

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Demyelinating polyneuropathies

• chronic inflammatory demyelinating polyneuropathy subacute development, muscle weakness in the proximal and distal parts of the extremities, often sensory disturbances, amyotrophy, hyporeflexia are noted;
• acute demyelinating inflammatory polyneuropathy (Guillain-Barré syndrome) acute development of muscle weakness, ascending type of disorders (muscles of the legs, pelvic girdle, trunk, respiratory, muscles of the shoulder, neck, possible involvement of the cranial muscles), rapid development of hyporeflexia, areflexia and sensory disorders.

When determining the activity of CPK, a normal or slightly elevated value of the indicator is sometimes noted.

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Polyradiculopathy (including diabetic)

Most often, there is unilateral muscle weakness, sensory disturbances in one or more dermatomes, possible dysfunction of the pelvic organs, and loss of tendon reflexes. When determining the activity of CPK, no deviations from the norm are found.

Kugelberg-Welander spinal muscular atrophy

Initial signs of the disease are noted at 4-8, less often - at 15-30 years: muscle atrophy, "ascending" type of lesion, fasciculations, tongue fibrillation, fine tremor of the fingers, pseudohypertrophy of the gastrocnemius muscles, involvement of paravertebral muscles in the pathological process. When determining the activity of CPK, a normal or slightly increased value of the indicator is sometimes noted.

Lesion at the level of the neuromuscular synapse

For diagnosis, it is necessary to examine neuromuscular transmission using a decrement test:

• myasthenia weakness predominantly in the proximal parts of the limbs. weakness of the neck muscles, respiratory muscles, sometimes involvement of cranial muscles (ptosis, diplopia, impaired chewing, swallowing, nasal voice), severe pathological muscle fatigue;
• Lambert-Eaton myasthenic syndrome (often observed in combination with lung carcinoma) - weakness and increased fatigue of the muscles of the proximal lower extremities (may be a generalized process), characterized by the symptom of "running in", cholinergic dysautonomia (lack of saliva and dry mouth).

Rhabdomyolysis

Massive muscle tissue necrosis may develop against the background of the above-mentioned pathological conditions. Its development may be facilitated by: excessive physical activity (especially in patients with metabolic myopathies), electrolyte disturbances, various infections, prolonged muscle compression, alcohol and cocaine intoxication, and medication intake. Clinical manifestations of rhabdomyolysis: myalgia, muscle weakness of varying severity. The course of rhabdomyolysis may be both short and long. Acute renal failure may develop in 16% of cases. Laboratory tests: myoglobinuria, significant increase in CPK activity.

Forms

Muscle weakness:

• proximal;
• distal;
• general.

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Diagnostics muscle weakness

It is extremely important to distinguish muscle weakness from increased fatigue and muscle pain. First of all, determination of creatine phosphokinase (CPK) activity, an increase in the indicator indicates myolysis. Needle EMG allows to distinguish primary muscle disease from neurological disorders causing muscle weakness.

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