A longitudinal study comparing thenar motor unit number estimates to other quantitative tests in patients with amyotrophic lateral sclerosis.

The following data were obtained on 21 amyotrophic lateral sclerosis (ALS) patients, aged 36-76 years (mean: 58 years), at baseline and months 4, 8, and 12: thenar motor unit number estimate (MUNE) using multiple point stimulation, mean thenar surface-recorded motor unit action potential negative-peak area, thenar compound muscle action potential amplitude, isometric hand grip strength, total Medical Research Council (MRC) manual muscle testing score, Appel ALS rating scale, and forced vital capacity (FVC). The absolute mean rate of change per month was significantly greater (P < 0.01) for MUNE values than for MRC and FVC values in the 21 ALS patients. In a subset of patients (n = 6) with slowly progressive disease, the absolute mean rate of change per month was significantly greater (P < 0.01) for MUNE values than for all other test values. In addition, MUNE values were the most sensitive index for documenting changes in disease progression over time.