[Alterations of previous potentials of somatosensory cerebral evoked potential after lesions of the brain-stem (author's transl)].

: The characteristics of previous potentials of somatosensory evoked potential in 12 patients with lesions of the brain-stem and in 24 normal individuals have been studied. Lesions of the brain-stem were confirmed by means of computerized axial tomography, arteriography or necropsy. According to data reported by other authors somatosensory evoked potential is anteceded by three previous potentials with central latencies of 10, 12, and 14 milliseconds. Brain-stem lesions which do not involve the medial lemniscus showed normal potencials, while extensive lesions of the protuberance abolish P-12 potential and increase central latencies of P-14 and somatosensory evoked potential. P-12 potential originates in the medial lemniscus and P-14 potential in the thalamic nuclei. The present results confirm the interest of previous potentials of somatosensory evoked potential, as well as other neurophysiologic techniques, in the evaluation of lesions of the brain-stem.