Evoked Potential Recording: An Adjunct to Human Stereotactic Surgery

The localization of various brain structures during stereotactic surgery is dependent upon stereotactic atlases used in conjunction with demonstrable radiographic landmarks. Because of the considerable anatomical variability encountered in humans, this localization is only an approximation. For animal studies electrode positions can be confirmed histologically at necropsy. Routine techniques have been developed for animal neurophysiologic recording but have not been extensively applied to humans. This paper presents a method for recording human evoked potentials from various thalamic nuclei. Peripheral stimulation and stimulation within the brain are used to evoke depth and scalp potentials. The evoked responses are averaged at various well-known thalamic nuclei, e.g., ventral posterior lateral (VPL), ventral posterior medial (VPM), centre median (CM), that have characteristic responses. These nuclei, in conjunction with radiographic information, are used as landmarks to aid location of other brain structures.