Stimulation-evoked pain and temperature sensations in thalamus of pain and non-pain patients

grantor: University of TorontoThis thesis examined the location and incidence of thalamic microstimulation-evoked painful/thermal sensations in pain and non-pain patients. Awake patients undergoing functional stereotactic surgery were asked to report any sensations evoked by microstimulation (300Hz, 0.2ms, 1 sec. trains) at 1-mm intervals along microelectrode trajectories through ventrocaudal nucleus (Vc) and ventroposterior (VPVc) region. In 49 movement-disorder and 37 pain patients microstimulation evoked painful/thermal sensations at 6.6% of the 5842 stimulation sites. The majority (77.3%) of these pain/temperature sites was located ventroposterior to Vc. The incidence of pain sites was higher in post-stroke pain patients (PSP, n = 11) compared to other patients (15.1% vs 1.6% in Vc; 9.5% vs 2.8% in VPVc). In contrast, thermal sites within VPVc were evoked less frequently in PSP patients (2.3%) than in other groups (7.4%). These data demonstrate that most pain/thermal sites were located in VPVc and suggest that alterations in thalamocortical sensory processing in PSP patients may mediate chronic pain.M.Sc