Symptoms of defeat of the brachial plexus and its branches

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

Primary bundles of the brachial plexus pass between the front and middle stair muscles and are sent to the supraclavicular fossa, located above and behind the subclavian artery. Further, the plexus passes under the collar bone and the axillary cavity. Here, each of the primary beams is divided into two branches: the front and the back. Connecting together, they form three secondary beams surrounding a. Axillaris from the outside, from behind and from above. The outer secondary beam is formed by the front branches CV - СVI - СVII; it is located lateral from the axillary artery. From this beam originate the musculocutaneous nerve and part of the median nerve (the upper leg is from CVII).

The posterior secondary fascicle is formed by the posterior branches of the three primary bundles and is located posteriorly from the a. Axillaris. From it begin the radial and axillary nerves.

The inner secondary bundle is formed from the anterior branches of the lower primary fascicle, located medially from a. Axillaris. From it extend the ulnar nerve, skin dermal medial nerve of the shoulder, dermal medial nerve of the forearm and part of the median nerve (inner leg, from the СIII-ТI).

The brachial plexus by means of rami communicantes is associated with the sympathetic trunk (middle or lower cervical node). The plexus is divided into two parts: supraclavicular and subclavian. From different places of the supraclavicular part of the brachial plexus, short branches extend to the muscles of the neck and waist of the upper extremities (except for the trapezius muscle). From the subclavian part of the plexus come out long branches that innervate the muscles and skin of the upper limb. Short cervical motor branches innervate: interdigit menses; the long neck muscle (with one-sided cutting tilts the cervical spine aside, with the bilateral one - bends it, participates in the turn of the neck); anterior, middle and posterior staircase muscles (with a fixed neck raise I-II ribs, with a fixed thorax cushion the cervical spine in its direction, with a two-sided contraction tilt it forward).

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

Tests to determine the strength of pectoral muscles:

1. the patient in a standing or sitting position is offered to lower and bring the upper limb raised above the horizontal line; the examiner is resisting this movement and palpating the contracted clavicular part of the muscle
2. suggest the lead raised to the horizontal plane of the upper limb; the examiner is resisting this movement and palpating the shortened sternum-rib part of the muscle.

These tests are examined with the upper limb raised above the horizontal line. Another way to study this muscle is when the upper limbs are below the horizontal line. The subject is offered to withdraw the upper limb, bend it slightly at the elbow joint and fix it in this position; The examiner tries to divert the upper limb to a maximum.

Isolated lesion mm. Thoracales anteriores are rare. Due to paralysis of the large pectoral muscle, it is difficult to bring the upper limb to the chest; the patient can not put the upper limb of the affected side on a healthy shoulder. It is also difficult to lower the raised upper limb (for example, the action necessary to prirubke firewood). Defined by hypotension, hypotrophy or atrophy of the anterior pectoral muscle.

The back nerves of the thorax (nn. Thoracales posteriores) include two trunks: the back nerve of the scapula and the long nerve of the thorax.

The back nerve of the scapula supplies the rhomboid muscle and the muscle that lifts the scapula. The rhomboid muscle brings the scapula closer to the spinal column and slightly lifts it.

The test for determining the strength of the diamond-shaped muscle: a patient in a standing position is offered to put his hands on the waist, bring the shoulder blades and bring the elbows to the rear as close as possible; the examiner is resisting this movement and palpating the contracted muscle along the vertebral margin of the scapula. With the paralysis of this muscle, the scapula is displaced downward, its lower corner moves outward and slightly behind the thorax.

The muscle lifting the scapula lifts the upper-internal angle of the scapula.

A test to determine its action: they suggest lifting the foreleg and moving it to the inside; the examiner palpates the contracted muscle.

The long nerve of the thorax is formed from the posterior fascicles of the supraclavicular part of the superior primary trunk of the brachial plexus. The nerve runs along the front surface of the middle staircase behind the brachial plexus and along the lateral wall of the thorax approaches the anterior dentate muscle. With the contraction of this muscle (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 lift the upper limb above the horizontal plane.

A test to determine the action of this muscle: the person in the sitting or standing position is suggested to lift the upper limbs above the horizontal plane. Normally, with this motion, the scapula rotates around the sagittal axis, is withdrawn from the spinal column, its lower corner rotates forward and laterally, adjacent to the thorax. In case of paralysis of this muscle, the scapula approaches the spine, its lower corner is separated from the thorax ("pterygoid shoulder"), the shoulder and shoulder are elevated in comparison with the healthy side. With the retraction of the upper limb or raising it anteriorly to the horizontal level, the wing-like distance of the scapula sharply increases, it is difficult to lift the upper limb above the horizontal plane. Sharply strengthens the wing-like distance of the scapula movement of the upper limb forward when resisting this action.

The main symptoms of the lesion of the long nerve of the chest are a difficult lifting of the upper limb above the horizontal level, the approach of the inner edge of the scapula to the vertebral column and the removal of the lower angle of the scapula from the chest, muscle atrophy. Isolated lesion of this nerve occurs relatively often because the nerve is superficially and can easily be damaged by compression by a backpack, other heavy objects, with bruises, ischemia, wounds, etc.

The suprascapular nerve (n. Suprascapularis) is formed from CV-CVI spinal nerves. Moving away from the posterior sections of the superior trunk of the primary bundle 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 scapula of the scapula under the trapezius muscle. Then the nerve is divided into branches, the sensitive part of which supplies the ligament and capsule of the shoulder joint, the motor - the supraspinatus and the subacute muscle.

A muscular muscle contributes to the retraction of the shoulder at an angle of 15 °.

Test for determining the strength of the supraspinous muscle: the patient in the standing position is offered to pull the shoulder at an angle of 15 °; the examiner is resisting this movement and palpating the contracted muscle in the paranasal fossa.

The subordinate muscle rotates the shoulder outward.

Test for determining the strength of the subacute muscle: the subject is offered to stand in the standing position, bent at the elbow joint, the upper limb to turn outward; the examiner is resisting this movement and palpating the contracted muscle in the subacute.

The loss of the function of these muscles is usually compensated fairly well. Difficulty of supination of the shoulder can only affect the performance of actions associated with frequent rotation of the shoulder outside, especially with a bent forearm (with sewing, etc.). It is characteristic of the westernization of the supra- and subacute fossa due to the atrophy of these muscles.

For chronic nerve damage, the width of the U-shaped notch on the upper edge of the scapula is pathogenetic. It ranges from 2 cm to several mm. Above the neckline, like a roof, the transverse ligament of the scapula is thrown.

With the defeat of the nasal cavity, complaints first appear on the "deep" pains above the upper edge of the scapula and in the outer part of the shoulder joint. They arise mainly in the vertical position of the body and when the patient lies on the affected side. When moving, there are pains of a pulling nature, which become shooting, especially when leading the upper limb from the trunk to the side. Pain can radiate into the neck. The defeat of the motor fibers leading to the subacute muscle leads to a weakness in the removal of the upper limb in the shoulder joint, especially at the beginning of the lead (angle to 15 °). Falling out of the function of the subacute muscle leads to a distinct weakness of the external rotation of the shoulder, which causes the pronation position of the hanging upper limb. External rotation of the shoulder is not completely disturbed, since in this movement the deltoid and small round muscles also participate. Nevertheless, the volume of rotation of the shoulder to the outside is reduced; also shows weakness of raising the upper limb forward in the first phase. As a result of limiting movements in the shoulder joint, it is difficult for patients to bring a spoon to the mouth, they can not comb their hair. With right-hand paresis, the larvae are forced to move a piece of paper to the left if they are trying to write quickly. There may be atrophy of the supraspinatus and subacute muscles (the latter is more noticeable). The peripheral features of the paresis of these muscles can be confirmed by electromyography.

The subscapular nerves (nn. Subscapulares) provide a subscapular and a large circular muscle. The subscapular muscle rotates the shoulder inwards (innervated by CV-CVII by spinal nerves). A large round muscle also rotates the shoulder inwards (pronation), pulls it back and leads to the trunk.

The test for determining the strength of the subscapular and large round muscles: the subject is offered to rotate the shoulder inward with the upper limb bent at the elbow joint; the examiner is resisting this movement. Reduction of strength in the performance of this test compared with the healthy side, indicates the defeat of the subscapular nerves. Moreover, the upper limb is excessively rotated outwards and can hardly be brought to a normal position.

The thoracic nerve (the posterior thoracic nerve, n. Thoraco-dorsalis) supplies the widest back muscle (innervated by CVII - СVIII), which leads the shoulder to the trunk, pulls the arm back to the middle line, rotating it inside (pronation).

Tests to determine the strength of the latissimus muscle of the back:

1. the person in the standing or sitting position is offered to lower the shoulder raised to the horizontal level; the examiner is resisting this movement and palpating the contracted muscle;
2. the subject is offered to lower the raised upper limb downward and backward, rotating it inwards; the examiner is resisting this movement and palpating the contracted muscle at the lower angle of the scapula. When this mice is paralyzed, the movement of the upper limb is difficult to reverse.

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

Axillary nerve (n. Axillaris) - the thickest of the short branches of the brachial plexus, is formed from the fibers of the spinal nerves CV-CVI. Penetrates with a. Circumflexa humeri posterior through foramen quadrilaterum on the posterior surface of the surgical neck of the humerus and gives branches to the deltoid and small round muscles, to the shoulder joint.

The deltoid muscle, when its anterior part is contracted, pulls the raised upper limb forward, the middle one - withdraws the shoulder to the horizontal plane, the posterior pulls the raised shoulder back.

The test for determining the strength of the deltoid muscle: the examinee in standing or sitting position suggests lifting the upper limb to the horizontal plane; The examiner exerts a resistance to this movement and palps the contracted muscle.

A small round muscle contributes to the rotation of the shoulder outside.

On the back edge of the deltoid muscle from the axillary nerve leaves the cutaneous branch - n. Cutaneus brachii lateralis superior, which supplies the skin in the deltoid region and on the posterior-outer surface of the upper third of the shoulder. The defeat of the nerve is possible in the area of the quadruple or in the place of exit into the subcutaneous tissue, at the edge of the deltoid muscle. Such patients complain of pain in the shoulder region, which are aggravated by movement in this joint (removal of the upper limb to the side, external rotation). The weakness and hypotrophy of the deltoid muscle is joined, its mechanical excitability is increased. With paralysis of this muscle, it is impossible to withdraw the upper limb to the side, lifting it forward and back; the upper limb "hangs like a whip". Hypesesia is detected in the deltoid region. A positive symptom is the compression of the exit site under the skin of the sensitive branch of this nerve. The differential diagnosis is carried out with a shoulder periarthrosis (in which the mobility of passive movements in the shoulder joint is limited, palpation is painful in the places of attachment of ligaments and muscles near the articular surface of the shoulder, there is no disturbance of sensitivity) and with discogenic cervical radiculitis (there are positive symptoms of tension of the spinal roots, a symptom of the increase in compression in the intervertebral foramen - a symptom of Spilane, Stein-brocker, etc.).

The musculocutaneous nerve (n. Muscutocutaneus) departs from the lateral bundle of the brachial plexus, located outside of a. Axillaris, follows down, perforates the coracoid-brachial muscle and is sent to the elbow joint between the biceps and brachial muscles. This nerve supplies the biceps arm muscle (innervated by the CV-CVI segment), coracoid-brachial (innervated by the CVI-CVII segment), and the brachial (innervated by the CV-CVII segment) muscles.

The biceps arm muscle flexes the upper limb in the elbow joint, suppinging the forearm.

The test for determining the strength of the biceps: the subject is offered to flex the upper limb in the elbow joint and to supine the pre-penetrated forearm; The examiner is resisting this movement and palpating the contracted muscle.

The bilious-brachial muscle helps lift the shoulder forward.

The brachial muscle bends the upper limb in the elbow joint.

The test for determining the strength of the shoulder muscle: the subject is offered to bend the upper limb in the elbow joint and to supine a previously slightly perforated forearm; The examiner is resisting this movement and palpating the contracted muscle.

At the outer edge of the tendon of the biceps arm muscle, the musculocutaneous nerve perforates the fascia of the forearm and continues downward under the name of the outer cutaneous nerve of the forearm, which is divided into two branches, the anterior and posterior.

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

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

Thus, the musculocutaneous nerve, in its function, is mainly the flexor of the forearm. When it is turned off, partial flexion in the elbow joint is preserved in the position of pronation due to the contraction of the humerus muscle (innervated by the median nerve) and due to the innervation of the biceps muscle by the two nerves - the musculo-dermal and the median.

When the musculocutaneous nerve is injured, the strength of the forearm flexors is weakened, the reflex from the biceps muscle weakens or appears hypotension and atrophy of the anterior muscles of the shoulder, the sensitivity in the zone of its branching decreases. This nerve is affected by a dislocation in the shoulder joint, fracture of the shoulder, compression during sleep or anesthesia, with wounds, infectious diseases and with prolonged physical exertion (back-sailing, playing tennis, etc.).

The medial cutaneous nerve of the shoulder (n. Cutaneus brachii mediales) is formed from the medial bundle of the brachial plexus and consists of sensitive fibers of spinal nerves СVIII-TI. It passes in the armpit medially from a. Axillaris and, being located subcutaneously, supplies the medial surface of the shoulder to the elbow joint.

At the level of the armpit, this nerve often connects with the perforating branch of the second thoracic nerve (n., Intercosto-brachialis). One or both of these nerves can be squeezed when walking on crutches, as well as with an aneurysm of the axillary artery and in the cicatricial processes of the upper third of the shoulder (along the medial surface) after wounds. Clinical signs are paresthesia and pain along the medial surface of the shoulder, reducing pain, tactile and temperature sensitivity in the zone of paresthesia. Diagnostics is promoted by tests of effleurage, finger compression and elevation.

The medial cutaneous nerve of the forearm (n. Cutaneus antebrachii medialis) is formed by sensitive fibers of the spinal nerves СVIII-TI, moves away from the medial bundle of the brachial plexus and passes in the armpit next to the ulnar first. At the level of the upper part of the shoulder, it is located medially from the brachial artery next to v. Basilica, together with which it perforates the fascia and becomes subcutaneous. So 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 perforation of the fascia in the upper third of the shoulder or in the cicatricial processes along the medial surface of the middle and lower third of the shoulder (after wounds, burns, surgeries). The clinical picture is characterized by growing pains, numbness and tingling along the medial surface of the forearm, gipalgesia in the same zone.

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