VEP and SEP in non-specific thalamic nuclei and pulvinar during stereotaxic surgery

This report is based on recordings of evoked photic (VEP) and somatosensory response (SEP) from the thalamic nuclei and cortex of 17 humans during stereotaxic surgery. The cortical SEP and VEP have relatively uniform patterns. The initial latency of the cortical VEP is shorter than that of SEP. Both thalamic SEP and VEP give relatively constant response to Limitans and Parafascicularis, Centromedian and Pulvinar but Dorsomedial nucleus has a smaller and variable latency. Thalamic SEP gives a better response than thalamic VEP in Nucleus Limitans and Parafascicularis, Nucleus Centromedian, and Pulvinar. This suggests that the non-specific thalamic nuclei, especially Centromedian, Limitans and the nucleus Parafascicularis and Pulvinar, play an important role in pain conduction and function as a relay station in the transmission of non-specific visual impulses. The visual evoked response pattern as well as somato-sensory evoked response from the thalamic nuclei can serve as a very reliable means of controlling the target area prior to subcortical destruction.