Motor unit number estimate-based rates of progression of ALS predict patient survival

We have examined, as predictors of survival in patients with amyotrophic lateral sclerosis (ALS), linear estimates of rates of disease progression (LEP), based on motor unit number estimates (MUNE). Motor unit number estimates of thenar, hypothenar, and extensor digitorum brevis muscles (according to the manual method of McComas), isometric grip and foot dorsiflexion (FD) strength, and forced vital capacity (FVC) were available in 34 patients. Linear estimates of rates of disease progression were derived. Probability of survival was calculated using the Kaplan-Meier method. Motor unit number estimates, LEP based on MUNE, and demographic characteristics were tested as risk factors within the Cox Proportional Hazards Model, using regression techniques. Individually, all MUNE-based LEP were highly significant (P < 0.00005); bulbar onset attained modest significance (P = 0.044). Secondary analysis showed MUNE-based LEP were more significant than regionally concordant function-based LEP. Linear estimates of rates of disease progression based on MUNE may thus predict survival of patients with ALS better than LEP based on function.