Manual of Surgery Volume First: General Surgery. Sixth Edition.

by Alexis Thomson; Alexander Miles

In the brachial birth-paralysis met with in infants, the lesion is due to over-stretching of the plexus, and is nearly always of the Erb-Duchenne type. The injury is usually unilateral, it occurs with almost equal frequency in breech and in vertex presentations, and the left arm is more often affected than the right. The lesion is seldom recognised at birth. The first symptom noticed is tenderness in the supra-clavicular region, the child crying when this part is touched or the arm is moved. The attitude may be that of the Erb-Duchenne type, or the whole of the muscles of the upper limb may be flaccid, and the arm hangs powerless. A considerable proportion of the cases recover spontaneously. The arm is to be kept at rest, with the affected muscles relaxed, and, as soon as tenderness has disappeared, daily massage and passive movements are employed. The reaction of degeneration can rarely be satisfactorily tested before the child is three months old, but if it is present, an operation should be performed. After operation, the shoulder should be elevated so that no traction is exerted on the affected cords.

The long thoracic nerve (nerve of Bell), which supplies the serratus anterior, is rarely injured. In those whose occupation entails carrying weights upon the shoulder it may be contused, and the resulting paralysis of the serratus is usually combined with paralysis of the lower part of the trapezius, the branches from the third and fourth cervical nerves which supply this muscle also being exposed to pressure as they pass across the root of the neck. There is complaint of pain above the clavicle, and winging of the scapula; the patient is unable to raise the arm in front of the body above the level of the shoulder or to perform any forward pushing movements; on attempting either of these the winging of the scapula is at once increased. If the scapula is compared with that on the sound side, it is seen that, in addition to the lower angle being more prominent, the spine is more horizontal and the lower angle nearer the middle line. The majority of these cases recover if the limb is placed at absolute rest, the elbow supported, and massage and galvanism persevered with. If the paralysis persists, the sterno-costal portion of the pectoralis major may be transplanted to the lower angle of the scapula.

The long thoracic nerve may be cut across while clearing out the axilla in operating for cancer of the breast. The displacement of the scapula is not so marked as in the preceding type, and the patient is able to perform pushing movements below the level of the shoulder. If the reaction of degeneration develops, an operation may be performed, the ends of the nerve being sutured, or the distal end grafted into the posterior cord of the brachial plexus.

The Axillary (Circumflex) Nerve.—In the majority of cases in which paralysis of the deltoid follows upon an injury of the shoulder, it is due to a lesion of the fifth cervical nerve, as has already been described in injuries of the brachial plexus. The axillary nerve itself as it passes round the neck of the humerus is most liable to be injured from the pressure of a crutch, or of the head of the humerus in sub-glenoid dislocation, or in fracture of the neck of the scapula or of the humerus. In miners, who work for long periods lying on the side, the muscle may be paralysed by direct pressure on the terminal filaments of the nerve, and the nerve may also be involved as a result of disease in the sub-deltoid bursa.

The deltoid is wasted, and the acromion unduly prominent. In recent cases paralysis of the muscle is easily detected. In cases of long standing it is not so simple, because other muscles, the spinati, the clavicular fibres of the pectoral and the serratus, take its place and elevate the arm; there is always loss of sensation on the lateral aspect of the shoulder. There is rarely any call for operative treatment, as the paralysis is usually compensated for by other muscles.

When the supra-scapular nerve is contused or stretched in injuries of the shoulder, the spinati muscles are paralysed and wasted, the spine of the scapula is unduly prominent, and there is impairment in the power of abducting the arm and rotating it laterally.

The musculo-cutaneous nerve is very rarely injured; when cut across, there is paralysis of the coraco-brachialis, biceps, and part of the brachialis, but no movements are abolished, the forearm being flexed, in the pronated position, by the brachio-radialis and long radial extensor of the wrist; in the supinated position, by that portion of the brachialis supplied by the radial nerve. Supination is feebly performed by the supinator muscle. Protopathic and epicritic sensibility are lost over the radial side of the forearm.

Radial (Musculo-Spiral) Nerve.—From its anatomical relationships this trunk is more exposed to injury than any other nerve in the body. It is frequently compressed against the humerus in sleeping with the arm resting on the back of a chair, especially in the deep sleep of alcoholic intoxication (drunkard's palsy). It may be pressed upon by a crutch in the axilla, by the dislocated head of the humerus, or by violent compression of the arm, as when an elastic tourniquet is applied too tightly. The most serious and permanent injuries of this nerve are associated with fractures of the humerus, especially those from direct violence attended with comminution of the bone. The nerve may be crushed or torn by one of the fragments at the time of the injury, or at a later period may be compressed by callus.

Clinical Features.—Immediately after the injury it is impossible to tell whether the nerve is torn across or merely compressed. The patient may complain of numbness and tingling in the distribution of the superficial branch of the nerve, but it is a striking fact, that so long as the nerve is divided below the level at which it gives off the dorsal cutaneous nerve of the forearm (external cutaneous branch), there is no loss of sensation. When it is divided above the origin of the dorsal cutaneous branch, or when the dorsal branch of the musculo-cutaneous nerve is also divided, there is a loss of sensibility on the dorsum of the hand.

The motor symptoms predominate, the muscles affected being the extensors of the wrist and fingers, and the supinators. There is a characteristic “drop-wrist”; the wrist is flexed and pronated, and the patient is unable to dorsiflex the wrist or fingers ([Fig. 90]). If the hand and proximal phalanges are supported, the second and third phalanges may be partly extended by the interossei and lumbricals. There is also considerable impairment of power in the muscles which antagonise those that are paralysed, so that the grasp of the hand is feeble, and the patient almost loses the use of it; in some cases this would appear to be due to the median nerve having been injured at the same time.