Suprascapular nerve entrapment

Abstract

Isolated compression of the suprascapular nerve is a rare entity, that is seldom considered in differential diagnosis of shoulder pain. Usually atrophy of supraspinatus and infraspinatus muscles is present, resulting in weakened abduction and external rotation of the shoulder. Mostly the patients do not note the paresis, but complain about a dull and burning pain over the dorsal shoulder region. In a proximal lesion (at level of the superior transverse scapular ligament) electromyography reveals changes in both muscles, while in a distal lesion (spinoglenoidal notch) only the infraspinatus shows a pathology. From 1996 to 2001 we diagnosed an isolated suprascapular entrapment in nine patients. Seven patients were operated: The ligament was removed and the nerve was neurolysed. The average age was 36 years. All patients showed pathological findings in electrophysiological and clinical examination. Five patients had an atrophy of both scapula muscles, two showed only infraspinatus muscle atrophy (one with a ganglion in the distal course of the nerve). Six patients were followed up. All showed an improvement. Pain disappeared and all patients were able to return to work and sport activities. Electrophysiological examination one year after operation revealed normal nerve conduction velocity. The number of motor units, however, showed a reduction by half compared to the healthy side. Lesions without history of trauma are usually caused by repetitive motion or posture. Weight lifting, volley ball and tennis promote the entrapment. Rarely a lesion (either idiopathic or due to external compression) is described for patients who underwent surgery. Patients with a ganglion or a defined cause of compression should be operated, patients who present without a distinct reason for compression should firstly be treated conservatively. Physiotherapy, antiphlogistic medication and avoiding of the pain triggering motion can improve the symptoms. However, if muscle atrophy is evident, an operation is indicated from our experience.