Evoked mechanical and electrical anal sphincter responses after cortical and lumbar magnetic stimulations.

In 13 healthy volunteers we recorded electrical and mechanical anal sphinct er (AS) evoked responses. Electrical responses were obtained with surface e lectrodes, and mechanical responses by anal manometry; all responses were c ompared with those of anterior tibialis. Mechanical evoked responses' laten cy and amplitude were calculated. The mean total conduction time of the ele ctrical responses was 26.07 ms at rest and 23.31 ms with mild contraction ( p < 0.003). After lumbar magnetic stimulations, because of stimulation arte fact, electrical responses couldn't be correctly measured. The mean central conduction time calculated with mechanical responses was 21,44 ms at rest and 18,81 ms with mild contraction (p < 0.003). The mean central conduction time to the anterior tibialis was shorter (14,38ms; p < 0.003). Evoked mec hanical responses', amplitudes were respectively 128,2 cm H2O (cortical sti mulations at rest), 138,8 cm H2O (cortical stimulations with mild contracti on) and 133,1 cm H2O (lumbar stimulations at rest) (NS). Evoked mechanical responses amplitudes were correlated with the AS maximal voluntary contract ion amplitude (p < 10(-4)). Mechanical motor evoked responses after cortica l and lumbar magnetic stimulations can be recorded and quantified. in anore ctal disorders, this technique could be of major interest for the diagnosis of neurologic lesions versus behavioural problems. (C) 2000 Editions scien tifiques et medicales Elsevier SAS.