Effects of medial thalamotomy and pallido-thalamic tractotomy on sleep andwaking EEG in pain and parkinsonian patients

Objectives: Investigation of sleep and sleep EEG before and after stereotac tic neurosurgery. Methods: All-night polysomnographic recordings were obtained in 3 neurogeni c pain patients and 3 parkinsonian patients. One subject of each group was recorded in addition 3 months after surgery. Stereotactic operations were p erformed in the medial thalamus and on the pallido-thalamic tract to reliev e neurogenic pain and parkinsonian symptoms, respectively. Results: Sleep efficiency was little affected by the surgical intervention in neurogenic pain patients and a dramatic reduction in REM sleep occurred, which had recovered in the subject recorded after 3 months. After the surg ery parkinsonian patients showed an increase in total sleep time and in sle ep efficiency, and a decrease in REM sleep latency. Sleep efficiency remain ed elevated in the 3 months follow-up. Medial thalamotomy abolished spindle frequency activity (SFA) in the power and coherence spectra in non-REM sle ep stage 2 systematically. Pallido-thalamic tractotomy attenuated SFA only to varying degrees. After 3 months SFA had reemerged. The alpha peak of the waking EEG was shifted to lower frequencies after surgery in 5 of 6 patien ts and had reverted to the original frequency 3 months later. Conclusions: Medial thalamotomy or pallido-thalamic tractotomy had acute an d reversible effects on the EEG and long-term deleterious side effects of s tereotactic surgery on sleep and sleep EEG are improbable. The results prov ide further evidence for the involvement of the human thalamus in the gener ation of sleep spindles. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.