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.