Muscle atrophy (amyotrophy) of the hand: causes, symptoms, diagnosis

Atrophy of the muscles (amyotrophia) of the hand in the practice of a neurologist is encountered in the form of secondary (more often) denervation atrophy (due to a violation of its innervation) and primary (less often) atrophy, in which the function of the motor neuron basically does not suffer ("myopathy"). In the first case, the pathological process can have different localization, starting from motoneurons in the anterior horns of the spinal cord (C7-C8, D1-D2), anterior roots, brachial plexus and ending with peripheral nerves and muscles.

One of the possible algorithms for differential diagnosis is based on the consideration of such an important clinical sign as one-sidedness or two-sidedness of clinical manifestations.

[1], [2], [3], [4], [5], [6]

The main causes of atrophy of the muscles of the hand:

I. One-sided atrophy of the muscles of the hand:

1. Carpal tunnel syndrome with median nerve injury;
2. Neuropathy of the median nerve in the region of the circular pronator;
3. Neuropathy of the ulnar nerve (ulnar syndrome of the wrist, syndrome of the cubital canal;
4. Neuropathy of the radial nerve (supinatory syndrome, tunnel syndrome on the upper third of the shoulder);
5. Syndrome of stair muscles with compression of the upper part of the neurovascular bundle;
6. The syndrome of a small pectoral muscle (hyperabdition syndrome);
7. Upper thoracic aperture syndrome;
8. Plexopathies (others);
9. Pancost syndrome;
10. Amyotrophic lateral sclerosis (in the onset of the disease);
11. Complex regional pain syndrome ("shoulder-brush" syndrome, "reflex sympathetic dystrophy");
12. Tumor of the spinal cord;
13. Syringomyelia (in the onset of the disease);
14. Syndrome hemiparkinsonism-hemiatrophy.

II. Two-sided atrophy of the muscles of the hand:

1. Amyotrophic lateral sclerosis;
2. Progressive spinal amyotrophy distal;
3. Hereditary distal myopathy;
4. Atrophy of the muscles of the hand
5. Plexopathy (rarely);
6. Polyneuropathy;
7. Syringomyelia;
8. Carpal tunnel syndrome;
9. Injury of the spinal cord;
10. Tumor of the spinal cord.

I. One-sided atrophy of the muscles of the hand

With carpal tunnel syndrome, hypotrophy develops in the muscles of the tenar (in the muscles of the thumb's elevation of the hand) with their flattening and restriction of the volume of active movements of one finger. The disease begins with pain and paresthesia in the distal parts of the hand (I-III, and sometimes all the fingers), and then hypodesa in the palmar surface of the 1st finger. The pains increase in the horizontal position or when the arm is raised. Motor disorders (paresis and atrophy) develop later, a few months or years after the onset of the disease. Characteristic of the Tynel symptom: when percussion with a hammer in the carpal canal area, paresthesias occur in the innervation of the median nerve. Similar sensations develop with passive maximum extension (Phalen's sign) or flexion of the hand, as well as during the cuff test. Typical are vegetative disorders on the hand (acrocyanosis, sweating disorders), a decrease in the speed of conduction along motor fibers. Almost half of all cases of carpal tunnel syndrome are bilateral and, as a rule, asymmetric.

Main causes: trauma (often in the form of professional overstrain with heavy manual labor), arthrosis of the wrist joint, endocrine disorders (pregnancy, hypothyroidism, increased secretion of STH in menopause), scarring, systemic and metabolic (diabetes mellitus) diseases, tumors, congenital stenosis carpal tunnel. Athetosis and dystonia in cerebral palsy are a possible (rare) cause of carpal tunnel syndrome.

Factors contributing to the development of carpal tunnel syndrome: obesity, diabetes, scleroderma, thyroid diseases, systemic lupus erythematosus, acromegaly, Paget's disease, mucopolysaccharidosis.

Differential diagnosis. Carpal tunnel syndrome sometimes has to be differentiated from sensory partial epileptic seizures, night dysesthesia, radiculopathy CV-SVIII, staircase syndrome. Carpal tunnel syndrome is sometimes accompanied by some vertebrogenic syndromes.

Neuropathy of the median nerve in the region of the round pronator develops due to the compression of the median nerve as it passes through the ring of the round pronator. There are paresthesias in the hand in the area of innervation of the median nerve. Hyposesthesia and paresis of the flexor of the fingers and muscles of the elevation of the thumb develops in the same zone (weakness of the thumb opposition, weakness of its abduction and paresis of the flexors of the II-IV fingers). With percussion and pressure in the area of the round pronator, soreness in this area and paresthesia in the fingers are characteristic. Hypotrophies develop in the zone of innervation of the median nerve, mainly in the area of elevation of the thumb.

Neuropathy of the ulnar nerve (ulnar syndrome of the wrist, syndrome of the cubital canal) in most cases is associated with tunnel syndrome in the elbow joint (compression of the nerve in the cubital Mushe canal) or in the wrist joint region (Guyon's canal) and manifests itself, in addition to atrophy in the IV-V region fingers (especially in the hypotenar area), pain, hypoesthesia and paresthesia in the ulnar parts of the hand, a characteristic symptom of effleurage.

The main causes: trauma, arthritis, congenital anomalies, tumors. Sometimes the cause remains unidentified.

Neuropathy of the radial nerve (supinatory syndrome, tunnel syndrome at the level of the spiral canal of the shoulder) is rarely accompanied by noticeable atrophies. Compression of the radial nerve in the spiral canal usually develops with a fracture of the shoulder. Sensitivity disorders are often absent. Typical local soreness in the compression zone. A "hanging or falling brush" is characteristic. The hypotrophy of the muscles of the back of the shoulder and forearm can be detected. When supinatorial syndrome, pain along the back surface of the forearm, wrist and hand is characteristic; there is a weakness of supination of the forearm, weakness of the extensors of the main phalanges of the fingers and paresis of the lead of the 1st finger.

Syndrome of stair muscles with compression of the upper or lower part of the neurovascular bundle (variant of plexopathy) may be accompanied by hypotrophy of the muscles of the hypotenar and, in part, of the tenar. The primary trunk of the plexus is compressed between the anterior and middle staircases and the first rib. Pain and paresthesia are observed in the neck, shoulder, shoulder and along the ulnar edge of the forearm and hand. Typical pain at night and day. It intensifies with a deep breath, with the head turning towards the side of the defeat and with the head tilted to the healthy side, with the arm leads. There is swelling and swelling in the supraclavicular area; soreness in palpation of a strained anterior staircase. Characteristic is the weakening (or disappearance) of the pulse to a. Radialis of a sore hand when turning the head and taking a deep breath.

The small pectoral muscle syndrome can also cause compression of the brachial plexus (a variant of plexopathy) under the tendon of the small pectoral muscle (hyperabdition syndrome). There are pains on the anteroposterior surface of the chest and in the hand; weakening of the pulse when laying the hand behind the head. Soreness in palpation of the small pectoralis muscle. There may be motor, vegetative and trophic disorders. Pronounced atrophy is rare.

The syndrome of the upper thoracic aperture is manifested by plexopathy (compression of the brachial plexus in the space between the first rib and the clavicle) and is characterized by weakness of the muscles innervated by the lower trunk of the brachial plexus, that is, the fibers of the median and ulnar nerve. The function of flexion of fingers and wrists suffers, which leads to a gross disruption of functions. Hypotrophy with this syndrome develops at late stages mainly in the hypotenar region . Pain sensations are usually located along the ulnar edge of the hand and forearm, but can be felt in the proximal and chest. The pain increases when the head is tilted to the side opposite to the strained staircase muscle. The subclavian artery is often involved (weakening or disappearing of the pulse with the maximum turn of the head in the opposite direction). In the region of the supraclavicular fossa, a characteristic swelling is revealed, with the compression of which pain in the arm region increases. Infringement of the trunk of the brachial plexus often occurs between the I rib and the collarbone (thoracic outlet). Syndrome of the upper aperture can be purely vascular, purely neuropathic or, more rarely - mixed.

Predisposing factors: cervical rib, hypertrophy of the transverse process of the seventh cervical vertebra, hypertrophy of the anterior staircase, deformation of the clavicle.

Plexopathy. The length of the brachial plexus is 15-20 cm. Depending on the cause, there may be syndromes of total or partial lesion of the brachial plexus. The defeat of the fifth and sixth cervical spine (C5-C6) or the superior primary trunk of the brachial plexus is manifested by Duchenne-Erb's paralysis. Pain and sensitivity disorders are observed in the proximal parts (the shoulder, neck, shoulder blade and in the deltoid muscle region). Characteristic paralysis and atrophy of the proximal muscles of the arm (deltoid, biceps arm, anterior brachial, large thoracic, supra- and subacute, subscapular, rhomboid, anterior dentate and others), and not the muscles of the hand.

The defeat of the eighth cervical and first thoracic root or the lower trunk of the brachial plexus is manifested by Dejerine-Clumpke paralysis. The paresis and atrophy of muscles innervated by the median and ulnar nerve, mainly the muscles of the hand, develops, except for those that are innervated by the radial nerve. Sensitive disorders are also observed in the distal parts of the hand.

It is necessary to exclude an additional cervical rib.

Known is also the syndrome of isolated involvement of the middle part of the brachial plexus, but it is rare and manifests itself as a defect in the zone of proximal innervation of the radial nerve with a preserved function m. Brachioradialis, which is innervated from the roots of C7 and Sb. Sensory disturbances can be observed on the posterior surface of the forearm or in the zone of innervation of the radial nerve on the posterior surface of the hand, but they are usually expressed minimally. In fact, this syndrome is not accompanied by atrophy of the muscles of the hand.

These plexopathic syndromes are characteristic for the defeat of the supraclavicular part of the brachial plexus (pars supraclavicularis). With the defeat of the same subclavian part of the plexus (pars infraclavicularis), there are three syndromes: a posterior type (defeat of the fibers of the axillary and radial nerves); lateral type (lesion of n. Musculocutaneus and lateral part of median nerve) and middle type (weakness of muscles innervated by ulnar nerve and medial part of median nerve, which leads to gross dysfunction of the wrist).

Causes: trauma (the most common cause), including generic and "backpack"; radiation exposure (iatrogenic); tumors; infectious and toxic processes; the Persononeja-Turner syndrome; hereditary plexopathy. Shoulder plexopathy, apparently of a dysimmune origin, is described in the treatment of botulinum toxin spasmodic torticollis.

Pancoast syndrome (Pancoast) is a malignant tumor of the apex of the lung with infiltration of the cervical sympathetic chain and brachial plexus, which manifests itself more often in adulthood with Horner's syndrome, which is difficult to locate by causal pain in the area of the shoulder, chest and arm (more often along the ulnar margin), followed by attachment of sensory and motor manifestations. Characteristic limitation of active movements and atrophy of the muscles of the hand with loss of sensitivity and paresthesia.

Amyotrophic lateral sclerosis in the onset of the disease is manifested by unilateral amyotrophy. If the process starts from the distal parts of the hand (the most frequent variant of the development of the disease), then its clinical marker is such an unusual combination of symptoms as one-sided or asymmetric amyotrophy (more often in the field of tenar) with hyperreflexia. In far-reaching stages, the process becomes symmetrical.

Complex regional type I pain syndrome (without peripheral nerve injury) and type II (with peripheral nerve injury). Obsolete names: "shoulder-brush" syndrome, "reflex sympathetic dystrophy". The syndrome is characterized mainly by a typical pain syndrome that develops after trauma or limb immobilization (in a few days or weeks) in the form of poorly localized drilling extremely unpleasant pain with hyperalgesia and allodynia, as well as local vegetative-trophic disorders (swelling, vasomotor and shipmotor disorders) with osteoporosis of the underlying bone tissue. Possible slight atrophic changes in the skin and muscles in the affected area. Diagnosis is carried out clinically; There are no special diagnostic tests.

A spinal cord tumor, especially the cerebrospinal cord, when placed in the anterior horn of the spinal cord as the first symptom can give local hypotrophy in the region of the muscles of the hand, followed by attachment and a steady increase in segmental paretic, hypotrophic and sensitive disorders, to which the symptoms of compression of long spinal cord conductors and cerebrospinal fluid.

Syringomyelia in the onset of the disease can be manifested not only by bilateral hypotrophy (and pain), but sometimes by unilateral symptoms in the hand area, which, as the disease progresses, become bilateral with the addition of other typical symptoms (hyperreflexia on the legs, trophic and characteristic sensory disorders).

The hemiparkinsonian hemiatrophy syndrome is a rare disease with unusual manifestations in the form of a relatively early onset (34-44 years) hemiparkinsonism, which is often combined with symptoms of dystonia on the same side of the body and "hemiatrophy of the body," by which its asymmetry is usually understood as a decrease the size of the hand and foot, less often - the trunk and face on the side of neurological symptoms. Asymmetry of the hands and feet is usually seen from childhood and does not affect the motor activity of the patient. With CT or MRI of the brain, in about half the cases, the lateral ventricle and cortical fissures of the cerebral hemispheres are enlarged on the side opposite to hemiparkinsonism (less often the atrophic process in the brain is revealed from both sides). The cause of the syndrome is hypoxic-ischemic perinatal damage to the brain. The effect of levodopa is observed only in some patients.

II. Bilateral atrophy of the muscles of the hand

Disease of motor neuron (BAS) at the stage of detailed clinical manifestations is characterized by bilateral atrophy with hyperreflexia, other clinical signs of lesion of spinal cord motoneurons (paresis, fascination) and / or brain stem and corticospinal and corticobulbar tracts, progressive course, and also characteristic EMG- a picture including in clinically preserved muscles.

Progressive spinal amyotrophy at all stages of the disease is characterized by symmetric amyotrophy, absence of symptoms of involvement of pyramidal tracts and other brain systems in the presence of EMG signs of motor neuron anterior horn of the spinal cord (motor neuronopathy) and relatively favorable course. Most forms of progressive spinal amyotrophy (PSA) affect mainly the legs, but there is a rare option (type V of distal PSA) with a predominant lesion of the upper limbs ("Aran-Duchenne brush").

Hereditary distal myopathy has similar clinical manifestations, but without clinical and EMG manifestations of involvement of the anterior horns of the spinal cord. Usually, an appropriate family history is identified. On EMG and with muscle biopsies, indication of muscular lesion level.

Plexopathy (rarely) brachial can be bilateral and total with some traumatic effects (crutch injury, etc.), an additional rib. A pattern of bilateral flaccid paresis with the limitation of active movements, diffuse atrophies including in the region of the hands and bilateral sensory disturbances is possible .

In the syndrome of the upper aperture, the syndrome of "lowered shoulders" (more often in women with a characteristic constitution) is described.

Polyneuropathy with the predominant defeat of the upper limbs is characteristic for intoxication with lead, acrylamide, in contact with the skin with mercury, hypoglycemia, porphyria (the hands are affected primarily and mainly in the proximal areas).

Syringomyelia in the region of the cervical thickening of the spinal cord, if it is predominantly anterolateral, is manifested by bilateral atrophy of the muscles of the hand and other symptoms of flaccid paresis in the hands, dissociated by sensitivity disorders by segmental type and, as a rule, pyramidal insufficiency on the legs. MRI confirms the diagnosis.

Carpal tunnel syndrome can often be observed from two sides (occupational trauma, endocrinopathy). In this case, the atrophy in the zone of innervation of the median nerve will be bilateral, more often - asymmetric. In these cases, a differential diagnosis with polyneuropathy is necessary.

Trauma of the spinal cord at the stage of residual phenomena can be manifested by a picture of complete or partial damage (interruption) of the spinal cord with the formation of cavities, scars, atrophy and fusion with a wide variety of symptoms, including atrophy, flaccid and central palsy, sensory and pelvic disorders. The data of the anamnesis usually do not give rise to diagnostic doubts.

Tumor of the spinal cord. Intramedullary primary or metastatic tumors affecting the anterior spinal cord horns (ventrally located) cause atrophic paralysis along with symptoms of compression of the lateral columns of the spinal cord with conductive sensory and motor symptoms. Progressive segmental and conduction disorders with impaired pelvic organs, as well as CT or MRI data help to make the correct diagnosis.

Differential diagnosis in such cases is often carried out primarily with syringomyelia.

Rare syndromes include congenital isolated tenar hypoplasia, which in most cases is of a one-sided nature, but bilateral cases are also described. Sometimes it is accompanied by anomalies in the development of the bones of the thumb. Most of the observations described were sporadic.

Diagnosis of muscle atrophy of the hand

General and biochemical blood test; Analysis of urine; activity of muscle enzymes (mainly CK) in the blood serum; Creatine and creatinine in urine; EMG; speed of excitation on the nerves; muscle biopsy; radiography of the chest and cervical spine; CT or MRI of the brain and cervico-thoracic spine.

[7]