Physiologically controlled selective thalamotomy for the treatment of abnormal movement by Leksell's open system

In the course of stereotaxic thalamotomy by Leksell's open system in 20 cases of abnormal movement, recording and stimulation of the subcortical structures have been performed by means of two semimicro-electrodes introduced parallel to the frontal plane. Taking advantage of simultaneous recording and electrical stimulation through these two electrodes, several critical points in the caudate nucleus and thalamus have been clearly delineated. Thus in each individual case an outline of the thalamic configuration in the frontal plane could be obtained, so that the final therapeutic lesion was placed with good precision at the lower-most border of VL or Vim nucleus. It has been shown that the physiologically determined minimum lesion resulted in satisfactory alleviation of the abnormal movements without notable untoward effects.