Effects of startle and laughter in cataplectic subjects: a neurophysiological study between attacks

Objectives: Cataplexy, when unequivocally present together with excessive d aytime sleepiness, is diagnostic for narcolepsy. Unfortunately, it is diffi cult to induce cataplexy during consultation. In this study we tried to ass ess presumed subclinical expressions of cataplexy using neurophysiological tests. Methods: In this controlled explorative study, we studied 14 patients with a clear history of cataplexy and 12 matched controls using standard H-refle x, H/M ratios, audiospinal reflex, H-reflexes modulated by emotions and sta rtle reflexes. Results: H-reflexes were attenuated during laughter in patients as well as controls. Startle reflexes were increased in patients. Audiospinal reflexes were not influenced. Conclusions: The patterns found add relevant knowledge concerning pathophys iological mechanisms and involved brain areas in cataplexy, and may reflect subclinical expressions of cataplexy. The presumed specificity of the abol ishment of H-reflexes during cataplectic attacks is questioned by our findi ngs. The exaggerated startle reflex is in line with recent findings concern ing involved brain areas in narcolepsy. (C) 2000 Elsevier Science Ireland L td. All rights reserved.