Unilateral scapulohumeral muscular atrophy

A peculiar form of chronic spinal muscular atrophy is described, 5 unrelated young males developed muscle wasting of the left shoulder and upper arm region, mainly in the distribution of myotomes C5 and C6. This muscle atrophy remained confined to the primary site for 13-18 years, being followed in 4 cases by a mild muscle atrophy of the right upper arm or or the left forearm and hand and in 1 case by atrophy of the legs and the facial muscles. On EMG examination, muscle involvement was always found to be more widespread than on clinical examination. The repeated and extensive EMG examinations gave results typical of an anterior horn cell disease. Pyramidal signs were absent. During the observation period of 21-40 years the course was benign and at least partial working capacity was retained until retiring age.