Neurologic Conditions Of The Shoulder
The long thoracic nerve innervates the serratus anterior muscle (see Plate 1-13). The serratus anterior muscle has its origin in the anterior chest wall and then inserts along the medial border of the scapula with most of its fibers attaching to the distal third of the scapular body (see Plate 1-13).
When there is a lesion of the long thoracic nerve and weakness of the serratus anterior muscle, there is winging of the scapula. When severe, there is limitation of active elevation of the shoulder because of an unsta- ble scapula that is not able to appropriately rotate laterally and maintain its position along the chest wall. In this particular case, by using overactive rhomboid function and trapezius function the patient is trying to compensate for loss of the function of the serratus anterior muscle. When this lesion occurs as a result of a viral insult or closed trauma, then spontaneous recovery often occurs over a period of several months to a year. When recovery is either incomplete or results in significant long-term disability, then pectoralis major muscle transfer to the tip of the scapula is a well-defined and effective treatment.
Charcot arthropathy of the shoulder can be associated with severe destructive lesions of both the humeral head and glenoid and is often evident on radiographs as multiple-joint bony debris. In some cases this is associated with a cervical syrinx, resulting in loss of proprioception and proprioceptive fibers to the shoulder girdle. When there is loss of sense of joint position, normal activities and pain associated with injury are not perceived by the patient, resulting in severe destructive damage to the joint. Often the patients have much less pain and better function then what would be expected by the severity of the joint damage. Because of the underlying cause of the shoulder damage, joint replacement or any type of surgical reconstruction has a high rate of complications, including prosthetic dislocation, periprosthetic fractures, and loosening of the prosthetic components.
Suprascapular nerve lesions can be associated with entrapment of the suprascapular notch or spinal glenoid notch. They can also be associated with ganglion cyst formation. This will result in weakness of external rota- tion and an external rotation lag sign (see Plate 1-40). Atrophy of the musculature of the supraspinatus fossa and infraspinatus fossa should be evaluated. Ganglion cyst formation can be associated with a superior labral tear (see Plate 1-51). The ganglion cyst forms as a synovial fluid-filled sac. When this ganglion encroaches on the suprascapular notch or spinoglenoid notch (see Plate 1-51) there is a suprascapular nerve compressive neuropathy.
These lesions can be treated by aspiration under image guidance. When treated by needle aspiration the ganglion can recur because the SLAP lesion is not repaired. Arthroscopic repair of the SLAP lesion can result in spontaneous resolution of the ganglion cyst. Alternatively, the SLAP lesion can be repaired arthroscopically with excision of the ganglion cyst. The clinical appearance for suprascapular neuropathy is severe atrophy of the supraspinatus or infraspinatus musculature. Isolated atrophy of the infraspinatus muscle is associated with entrapment of the infraspina- tus branch of the suprascapular nerve at the spinoglenoid notch.
Lesions of the spinal accessory nerve involve weakness or paralysis isolated to the trapezius muscle. Spinal accessory nerve lesions can also be associated with viral syndromes. They can also be seen as an iatrogenic lesion associated with cervical node biopsy. The shoulder demonstrates drooping of the scapula, noted as one shoulder not being level to the other, the neck contour is distorted, and the rhomboid muscles are prominently seen because the middle trapezius is atrophied. This lesion also causes winging of the scapula with predominate involvement of the upper half of the scapula and can be distinguished from the long thoracic nerve palsy with serratus anterior muscle weakness that affects predominately the lower pole of the scapula. Chronic lesions that are associated with incomplete or lack of recovery can be treated with transfer of the levator scapulae and rhomboid musculature (Eden-Lang procedure). This is an effective muscle transfer as a salvage procedure for this nerve and muscle lesion.