LONGITUDINAL-STUDY OF FIBER DENSITY AND MOTOR UNIT NUMBER ESTIMATE INPATIENTS WITH AMYOTROPHIC-LATERAL-SCLEROSIS

We examined fiber density, compound muscle action potential (CMAP) amp litude, and motor unit number estimate (MUNE) of the abductor digiti m inimi and grip strength longitudinally. We sought to determine the eff ects of ALS on these measurements and to Evaluate which of these tests may be more sensitive in evaluating progression of ALS and possibly p redicting survival. Ten patients were examined at months 0, 3, and 6. A significant decrease in MUNE and increase in fiber density were obse rved at months 3 and 6 (p < 0.02) compared with baseline (month 0). Me an CMAP and grip strength declined, but not significantly. The decreas e in MUNE over 6 months was significantly greater than that of CMAP an d grip strength (p < 0.025). The significant changes in MUNE and fiber density over time suggest that they are more sensitive in measuring t he rate of progression of ALS. To evaluate further the utility of thes e tests, we arbitrarily divided the patients into equal groups based o n length of survival. MUNE declined significantly in the group with sh orter survival (p < 0.01). Conversely, fiber density increased signifi cantly in patients with longer survival (p < 0.01). With similar stati stical analysis there were no significant differences in decline of CM AP or grip strength in either subgroup over 6 months. Our study sugges ts that MUNE and fiber density are more sensitive than CMAP and grip s trength in detecting progression of ALS. Furthermore, we raise the hyp otheses that a greater increase in fiber density identifies a group of patients with ALS who will have longer survival, and that a greater d ecline in MUNE identifies a group with a worse prognosis.