EFFECT OF CHRONIC ELECTRICAL-STIMULATION OF THE CENTROMEDIAN THALAMICNUCLEI ON VARIOUS INTRACTABLE SEIZURE PATTERNS .2. PSYCHOLOGICAL PERFORMANCE AND BACKGROUND EEG ACTIVITY

We studied the effect of electrical stimulation of centromedian thalam ic nuclei (ESCM) on seizure control and paroxysmal EEG activity in 23 patients. We report the effect of chronic ESCM on psychological perfor mance and background EEG activity of patients with various intractable seizure patterns. In each patient, a simple specifically designed neu ropsychological scales (one for adults and one for children) was admin istered at the end of the baseline (BL), ESCM, and poststimulation (Po st) periods; and 14 consecutive EEG recordings during these periods we re performed to determine the degree of neuropsychological improvement and the temporal course of EEG changes. A significant increase in psy chological scores and the number of background EEG waves per 10 s was noted in groups A (generalized tonic-clonic seizures, GTC), C (complex partial seizures, CPS), and D (generalized tonic seizures) and the to tal group of patients from BL to ESCM and from BL to Post periods. Gro up B patients showed a substantial increase (partial motor seizures) d uring the same periods. Improvement on psychological performance corre lated better with age and baseline degree of deterioration than with t he nature of the particular psychological improvement in any given sub test. The improvement in EEG background rhythm was most noticeable at the end of ESCM and at the beginning of the Post periods. Complete nor malization of neuropsychologic scores and EEG rhythms was rare, but im provement was significant for both. Psychological scores increased fro m BL 14 +/- 2 to ESCM 21 +/- 2 and Post 23 +/- 2 (normal expected 26), and EEG background rhythm increased from BL 42 +/- 2 to ESCM 62 +/- 2 and Post 54 +/- 2 EEG waves/10 s. (normal expected >80).