Influence of dorsal column stimulation upon human thalamic somatosensory-evoked potentials

2 patients with previously implanted dorsal column stimulators underwent basal thalamotomy for the treatment of pain, which provided the opportunity to record evoked potentials from the intralaminar (IL) and ventroposterolateral (VPL) areas of the thalamus. Short latency evoked potentials recorded from VPL were not influenced by dorsal column stimulation. However, very long latency (500 ms) potentials recorded bilaterally in IL were modified by stimulation of the dorsal columns of the spinal cord at frequencies between 20 and 40 HZ.