Send to

Choose Destination
Muscle Nerve. 1999 Jul;22(7):870-3.

Dissociated small hand muscle involvement in amyotrophic lateral sclerosis detected by motor unit number estimates.

Author information

Department of Neurology, Chiba University School of Medicine, Chiba 260-8670, Japan.


In some patients with amyotrophic lateral sclerosis (ALS), the thenar hand is more severely affected than the hypothenar hand. To quantify the dissociated involvement, we examined the motor unit number estimate (MUNE) of both the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles in 23 patients with ALS. Whereas ALS patients had significantly smaller MUNEs than normal subjects in both muscles, the extent of motor unit loss was significantly greater in the APB than ADM. Moreover, a simple comparison of the amplitude of compound muscle action potentials (CMAPs) showed that ALS patients had significantly smaller APB/ADM ratios than normal subjects and patients with cervical spondylotic amyotrophy, bulbospinal muscular atrophy, or peripheral neuropathy. The more severe involvement of the APB probably reflects the specific pathophysiology in ALS, and possible mechanisms for the dissociated involvement are discussed.

Comment in

Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center