Symptoms of lesions of the brachial plexus and its branches

Brachial plexus (plexus brachials). The plexus is formed by the anterior branches of the CIV - CV - CVIII and TI spinal nerves. Passing between the anterior and posterior intertransverse muscles, the nerve trunks join together and form three primary bundles of the brachial plexus: the upper (fasciculus superior, the junction of CV and CVI), the middle (fasciculus rnedius, a continuation of one CVII) and the lower (fasciculus inferior, the junction of CVIII and TI).

The primary bundles of the brachial plexus pass between the anterior and middle scalene muscles and are directed to the supraclavicular fossa, located above and behind the subclavian artery. Then the plexus passes under the clavicle and axillary fossa. Here each of the primary bundles divides into two branches: anterior and posterior. Connecting with each other, they form three secondary bundles surrounding a. axillaris from the outside, behind and above. The external secondary bundle is formed by the anterior branches of CV - CVI - CVII; it is located laterally from the axillary artery. The musculocutaneous nerve and part of the median nerve (the upper leg - from CVII) originate from this bundle.

The posterior secondary bundle is formed by the posterior branches of the three primary bundles and is located posterior to the a. axillaris. The radial and axillary nerves originate from it.

The internal secondary bundle is formed from the anterior branches of the lower primary bundle, located medially from a. axillaris. From it branch off the ulnar nerve, the cutaneous medial nerve of the arm, the cutaneous medial nerve of the forearm and part of the median nerve (the internal leg, from CVIII - TI).

The brachial plexus is connected with the sympathetic trunk (its middle or lower cervical ganglion) via the rami communicantes. The plexus is divided into two parts: supraclavicular and subclavian. Short branches extend from different places in the supraclavicular part of the brachial plexus to the muscles of the neck and shoulder girdle (except for the trapezius muscle). Long branches emerge from the subclavian part of the plexus, which innervate the muscles and skin of the upper limb. The short cervical motor branches innervate the intertransverse muscles; the longus colli muscle (with unilateral contraction, it tilts the cervical spine to the side, with bilateral contraction, it flexes it; it participates in turning the neck); the anterior, middle and posterior scalene muscles (with a fixed neck, they raise the 1st and 2nd ribs, with a fixed chest, they tilt the cervical spine to their side, with bilateral contraction, they tilt it forward).

The short nerves of the shoulder girdle are: the subclavian nerve (n. subclavius, from CV) - supplies the subclavian muscle, which pulls the clavicle down and medially; the anterior thoracic nerves (nn. thoracales anteriores, CV, CVIII, TI) - supply the pectoral muscles: the large (adducts and rotates the shoulder inward - pronation) and the small (pulls the scapula forward and downward).

Tests to determine the strength of the pectoral muscles:

1. the patient, in a standing or sitting position, is asked to lower and bring the upper limb raised above the horizontal line; the examiner resists this movement and palpates the contracted clavicular part of the muscle
2. They suggest bringing the upper limb raised to a horizontal plane; the examiner resists this movement and palpates the contracted sternocostal part of the muscle.

These tests are examined with the upper limb raised above the horizontal line. Another way to examine this muscle is with the upper limbs below the horizontal line. The subject is asked to abduct the upper limb, bend it slightly at the elbow joint and fix it in this position; the examiner tries to abduct the upper limb as much as possible.

Isolated lesions of mm. thoracales anteriores are rare. Due to paralysis of the pectoralis major muscle, it is difficult to bring the upper limb to the chest; the patient cannot place the upper limb of the affected side on the healthy shoulder. Lowering the raised upper limb is also difficult (for example, the action required to chop wood). Hypotonia, hypotrophy, or atrophy of the anterior pectoral muscle is determined.

The posterior nerves of the thoracic cage (nn. thoracales posteriores) include two trunks: the dorsal nerve of the scapula and the long nerve of the thoracic cage.

The dorsal scapular nerve supplies the rhomboid and levator scapulae muscles. The rhomboid muscle brings the scapula closer to the spinal column and slightly elevates it.

Test to determine the strength of the rhomboid muscle: the patient is asked to place his palms on his waist in a standing position, bring his shoulder blades together and bring his elbows as close together as possible from behind; the examiner resists this movement and palpates the contracted muscle along the vertebral edge of the scapula. When this muscle is paralyzed, the scapula moves downwards, its lower angle moves outwards and lags slightly behind the chest.

The levator scapulae muscle elevates the superior medial angle of the scapula.

A test to determine its action: they ask you to lift the shoulder girdle and move it inward; the examiner palpates the contracted muscle.

The long thoracic nerve is formed from the posterior bundles of the supraclavicular part of the upper primary trunk of the brachial plexus. The nerve runs along the anterior surface of the middle scalene muscle behind the brachial plexus and along the lateral wall of the chest approaches the anterior serratus muscle. When this muscle contracts (with the participation of the rhomboid and trapezius muscles), the scapula approaches the thorax; the lower part of the muscle rotates the scapula around the sagittal axis, helping to raise the upper limb above the horizontal plane.

A test to determine the action of this muscle: the subject in a sitting or standing position is asked to raise the upper limbs above the horizontal plane. Normally, with this movement, the scapula rotates around the sagittal axis, is abducted from the spinal column, its lower angle rotates forward and laterally, adjoining the chest. With paralysis of this muscle, the scapula approaches the spine, its lower angle is located away from the chest ("winged scapula"), the shoulder girdle and scapula are raised compared to the healthy side. When the upper limb is abducted or raised forward to a horizontal level, the wing-like protrusion of the scapula sharply increases, and raising the upper limb above the horizontal plane is difficult. The forward movement of the upper limb with resistance to this action sharply increases the wing-like protrusion of the scapula.

The main symptoms of damage to the long thoracic nerve are difficulty raising the upper limb above the horizontal level, the inner edge of the scapula approaching the spinal column and the lower angle of the scapula moving away from the chest, muscle atrophy. Isolated damage to this nerve is relatively common because the nerve is located superficially and can easily be damaged by compression with a backpack, other heavy objects, bruises, ischemia, wounds, etc.

The suprascapular nerve (n. suprascapularis) is formed from the CV-CVI spinal nerves. Having departed from the posterior sections of the upper trunk of the primary cord of the brachial plexus, this nerve goes down along the outer edge of the plexus to the supraclavicular fossa; at the level of the clavicle, it turns back and penetrates through the notch of the scapula under the trapezius muscle. Then the nerve divides into branches, the sensitive part of which supplies the ligaments and capsule of the shoulder joint, the motor part - the supraspinatus and infraspinatus muscles.

The supraspinatus muscle promotes shoulder abduction at an angle of 15°.

Test to determine supraspinatus strength: the subject is asked to abduct the shoulder at a 15° angle in a standing position; the examiner resists this movement and palpates the contracted muscle in the supraspinatus fossa.

The infraspinatus muscle rotates the shoulder outward.

Test for determining the strength of the infraspinatus muscle: the subject is asked to stand with the upper limb bent at the elbow and turn it outward; the examiner resists this movement and palpates the contracted muscle in the infraspinatus fossa.

The loss of function of these muscles is usually compensated quite well. Difficulty in shoulder supination may only occur when performing actions involving frequent outward rotation of the shoulder, especially with a bent forearm (when sewing, etc.). Typically, the supra- and infraspinous fossa is depressed due to atrophy of these muscles.

The width of the U-shaped notch on the upper edge of the scapula is of pathogenetic importance for chronic nerve damage. It ranges from 2 cm to several mm. The transverse ligament of the scapula is thrown over the notch like a roof.

When the subscapular nerve is affected, complaints of "deep" pain above the upper edge of the scapula and in the outer part of the shoulder joint initially appear. They occur mainly in the vertical position of the body and when the patient lies on the affected side. During movement, pains of a pulling nature occur, which become shooting, especially when the upper limb is abducted from the body to the side. The pains may radiate to the neck. Damage to the motor fibers going to the infraspinatus muscle leads to weakness of abduction of the upper limb in the shoulder joint, especially at the beginning of abduction (angle up to 15 °). Loss of function of the infraspinatus muscle leads to a distinct weakness of external rotation of the shoulder, due to which a pronation position of the drooping upper limb occurs. External rotation of the shoulder is not completely impaired, since the deltoid and teres minor muscles also participate in this movement. However, the volume of external rotation of the shoulder decreases; weakness in raising the upper limb forward in the first phase is also revealed. As a result of limited movement in the shoulder joint, patients have difficulty bringing a spoon to their mouth and cannot comb their hair. With right-sided paresis, the patient is forced to move a sheet of paper to the left if he tries to write quickly. Atrophy of the supraspinatus and infraspinatus muscles may occur (the latter is more noticeable). Peripheral features of paresis of these muscles can be confirmed by electromyography.

The subscapular nerves (nn. subscapulares) supply the subscapularis and teres major muscles. The subscapularis muscle rotates the shoulder inward (innervated by the CV-CVII spinal nerves). The teres major muscle also rotates the shoulder inward (pronation), pulls it back and brings it toward the torso.

Test to determine the strength of the subscapularis and teres major muscles: the subject is asked to rotate the shoulder inward with the upper limb bent at the elbow; the examiner resists this movement. A decrease in strength when performing this test compared to the healthy side indicates damage to the subscapular nerves. In this case, the upper limb is excessively rotated outward and can be brought to a normal position with difficulty.

The thoraco-dorsal nerve (dorsal thoracic nerve, n. thoraco-dorsalis) supplies the latissimus dorsi muscle (innervated by CVII - CVIII), which brings the shoulder to the body, pulls the arm back to the midline, rotating it inward (pronation).

Tests to determine the strength of the latissimus dorsi muscle:

1. the subject, in a standing or sitting position, is asked to lower the shoulder raised to a horizontal level; the examiner resists this movement and palpates the contracted muscle;
2. The subject is asked to lower the raised upper limb down and back, rotating it inward; the examiner resists this movement and palpates the contracted muscle at the lower angle of the scapula. When this muscle is paresis, backward movement of the upper limb is difficult.

From the subclavian part of the brachial plexus, one short and six long nerves begin to the upper limb.

The axillary nerve (n. axillaris) is the thickest of the short branches of the brachial plexus, formed from the fibers of the spinal nerves CV - CVI. It penetrates together with a. circumflexa humeri posterior through the foramen quadrilaterum to the posterior surface of the surgical neck of the humerus and gives branches to the deltoid and teres minor muscles, to the shoulder joint.

When the front part of the deltoid muscle contracts, it pulls the raised upper limb forward, the middle part pulls the shoulder to the horizontal plane, and the back part pulls the raised shoulder back.

Test to determine the strength of the deltoid muscle: the subject is asked to raise the upper limb to a horizontal plane in a standing or sitting position; the examiner resists this movement and palpates the contracted muscle.

The teres minor muscle helps to rotate the shoulder outward.

Along the posterior edge of the deltoid muscle, a cutaneous branch, n. cutaneus brachii lateralis superior, departs from the axillary nerve, which supplies the skin in the deltoid region and on the postero-outer surface of the upper third of the shoulder. Nerve damage is possible in the area of the quadrilateral opening or at the point of exit into the subcutaneous tissue, at the edge of the deltoid muscle. Such patients complain of pain in the shoulder joint, which intensifies with movement in this joint (abduction of the upper limb to the side, external rotation). Weakness and hypotrophy of the deltoid muscle join in, its mechanical excitability increases. With paralysis of this muscle, it is impossible to abduct the upper limb to the side, raise it forward and backward; the upper limb "hangs like a whip". Hypesthesia is detected in the deltoid region. The symptom of compression of the place where the sensitive branch of this nerve exits under the skin is positive. Differential diagnosis is carried out with shoulder periarthritis (in which mobility and passive movements in the shoulder joint are limited, palpation at the sites of attachment of ligaments and muscles near the articular surface of the shoulder is painful, there is no disturbance of sensitivity) and with discogenic cervical radiculitis (in this case, there are positive symptoms of tension of the spinal roots, a symptom of increasing compression in the intervertebral foramen - Spilaine's symptom, Steinbrocker's symptom, etc.).

The musculocutaneous nerve (n. muscutocutaneus) departs from the lateral cord of the brachial plexus, is located outside of a. axillaris, goes down, pierces the coracobrachialis muscle and goes to the elbow joint area between the biceps and brachialis muscles. This nerve supplies the biceps brachii (innervated by the CV-CVI segment), coracobrachialis (innervated by the CVI-CVII segment) and brachialis (innervated by the CV-CVII segment) muscles.

The biceps brachii muscle flexes the upper limb at the elbow joint, supinating the forearm.

Test to determine the strength of the biceps muscle: the subject is asked to flex the upper limb at the elbow joint and supinate the previously pronated forearm; the examiner resists this movement and palpates the contracted muscle.

The coracobrachialis muscle helps to raise the shoulder forward.

The brachialis muscle flexes the upper limb at the elbow joint.

A test to determine the strength of the shoulder muscle: the subject is asked to bend the upper limb at the elbow joint and supinate the slightly pronated forearm; the examiner resists this movement and palpates the contracted muscle.

At the outer edge of the biceps tendon, the musculocutaneous nerve pierces the fascia of the forearm and continues downward under the name of the external cutaneous nerve of the forearm, which divides into two branches - anterior and posterior.

The anterior branch innervates the skin of the outer half of the forearm to the eminence of the thumb muscle (thenar).

The posterior branch supplies the skin of the radial border of the forearm to the wrist joint.

Thus, the musculocutaneous nerve is primarily a flexor of the forearm. When it is switched off, partial flexion in the elbow joint is maintained in the pronation position due to the contraction of the brachioradialis muscle (innervated by the median nerve) and due to the innervation of the biceps muscle by two nerves - the musculocutaneous and median.

When the musculocutaneous nerve is damaged, the strength of the forearm flexors is weakened, the reflex from the biceps muscle is reduced or disappears, hypotension and atrophy of the anterior muscles of the shoulder appear, and sensitivity in the area of its branching is reduced. This nerve is damaged by a dislocation in the shoulder joint, a fracture of the shoulder, compression during sleep or anesthesia, wounds, infectious diseases, and prolonged physical exertion (swimming on the back, playing tennis, etc.).

The medial cutaneous nerve of the arm (n. cutaneus brachii mediales) is formed from the medial cord of the brachial plexus and consists of sensory fibers of spinal nerves CVIII - TI. It passes in the axillary bursa medially from a. axillaris and, located subcutaneously, supplies the medial surface of the arm to the elbow joint.

At the level of the axillary fossa, this nerve often connects with the penetrating branch of the second thoracic nerve (n. intercosto-brachialis). One or both of these nerves can be compressed when walking on crutches, as well as with an aneurysm of the axillary artery and with cicatricial processes in the upper third of the shoulder (along the medial surface) after injuries. Clinical signs are paresthesia and pain along the medial surface of the shoulder, decreased pain, tactile and temperature sensitivity in the paresthesia zone. Diagnosis is facilitated by tapping, finger compression and elevation tests.

The medial cutaneous nerve of the forearm (n. cutaneus antebrachii medialis) is formed by the sensory fibers of the spinal nerves CVIII - TI, departs from the medial bundle of the brachial plexus and passes in the axillary fossa near the first ulnar nerve. At the level of the upper part of the shoulder, it is located medially from the brachial artery near v. basilica, together with which it pierces the fascia and becomes subcutaneous. Thus, it descends to the medial surface of the forearm and innervates the skin of almost the entire medial surface of the forearm from the elbow to the wrist joint. The nerve can be damaged at the site of fascial perforation in the upper third of the shoulder or in cicatricial processes along the medial surface of the middle and lower third of the shoulder (after wounds, burns, operations). The clinical picture is characterized by increasing pain, numbness and tingling along the medial surface of the forearm, hypalgesia in the same area.

[ 1 ], [ 2 ], [ 3 ], [ 4 ]