EFFECTS OF ANTERIOR CORPUS CALLOSUM SECTION ON CORTICAL GLUCOSE UTILIZATION IN BABOONS

Abstract

Cortical glucose utilization was measured under light anaesthesia using positron emission tomography and ¹⁸F-fluorodeoxyglucose before and serially after stereotaxic anterior corpus callosum sectrion in 3 adult baboons (Papio papio); in 1 animal needles were introduced but callosotomy was not performed (‘sham’ operation). Lesion efficacy was verified by x-ray computerized tomography and by postmortem examination which indicated effective anterior two-thirds callosal section in all 3 baboons, as well as a small contusional area in the medial frontal cortex. A two-way layout analysis of variance performed on the regional cerebral metabolic rate of glucose (CMRG1c) data obtained in the frontotemporal, temporal and occipital areas revealed significant effects for both the time and the region factors (P < 0.0000 I for each); the time effects indicated a significant initial metabolic depression (P < 0.01) at day 11 and 18, and a subsequent recovery (P < 0.01 to 0.05) at day 98. Average CMRGIc changes from preoperative values at successive studies were-23%, -27%, -17%, -8% and + 2%, and -17%, -21%, -10%, -5% and + 6% in the ’surgically approached‘ and the contralateral frontotemporal area, respectively. The frontotemporal/occipital CMRGIc ratio was significantly depressed at days 11, 18 and 32 (P < 0.01, 0.01 and 0.05, respectively), indicating a transient postoperative alteration in the cortical metabolic pattern. In the ’sham‘ animal, surgery induced negligihle metabolic effects. Our results indicate that effective anterior corpus callosum section induces a transient bilateral depression of cortical metabolism, which predominates in the anterior parts of the brain, while metabolic recovery suggests efficient noural adaptation. These functional effects in the cortex may underlie the transient behavioural changes that follow anterior callosotomy in man.