Motor potentials of lower-lip mimetic muscles and distal arm muscles to cortical transcranial magnetic stimulation: The possibility of one-dimensional separation of two cortical representation areas

The cortical representation of the abductor pollicis brevis muscle (APB) wa s investigated by transcranial magnetic stimulation (TMS) along the interau ral line on the head surface in 17 healthy subjects. Comparing amplitudes o f motor evoked potentials (MEPs) with those obtained by cortical TMS of low er-lip muscles, we found a considerable overlap between the areas from whic h reproducible MEPs of APE and lower-lip muscles could be elicited. However , there was a statistically significant separation of the two areas, the AP E area being placed more medially. With regard to short examination procedu res it can be concluded that a separation between distal arm and facial mus cles is possible not only by two-dimensional cortical mapping procedures, b ut also by one-dimensional cortical TMS. Copyright (C) 2000 S. Karger AG, B asel.