Photic EEG-driving responses in thalamotomized and medicated cases of Parkinson's disease.

EEG-driving responses to visual stimulation were studied using EEG Interval Spectrum Analysis (EISA) before and after stereotaxic thalamotomy and Nacom (L--Carbidopa and Levodopa) treatment of 67 Parkinson patients. Five types of photic-driving responses were distinguished in the EISA results: (1) all-band response, (2) Beta-dominant, (3) Alpha-Beta-dominant, (4) Alpha-Theta-dominant, (5) non-response. Twenty patients received a daily dose of 750--1000 mg of Nacom orally, and 47 patients 1000--1500 mg for a period of 3 to 4 weeks. In most cases the medication produced no change in photic-driving and EEG patterns. The photic-driving response showed no significant correlation with clinical signs and background EEG. Unilateral thalamotomy was performed in ten Parkinson patients. In two of these patients the EEG-driving response diminished in the first post-operative week for low frequency stimuli but increased after the second week.