Lack of cervical paraspinal muscle involvement in juvenile distal spinal muscular atrophy: an electromyographic study on 15 cases.

Electromyography (EMG) of the lower cervical paraspinal muscles was performed in 15 young Chinese males with distal spinal muscular atrophy of the upper extremities. The lack of fibrillation and positive sharp waves in all patients, both in early or active and chronic or steady stages, did not correlate with the EMG status in the affected upper extremity on the same side. This finding is in striking contrast with that in amyotrophic lateral sclerosis.