Abstracts

RATIONALE: In a previous work, we have shown that the antiepileptic effect of the subacute electrical stimulation of the hippocampus (SAHCS) correlates with electrophysiological signs of hippocampal inhibition: increased threshold, decreased amplitude and flattened down of the recovery cycles of the hippocampal responses evoked by amygdaloid stimulation. In addition, prolonged SAHCS (560 hs., or more) increased threshold and decreased duration of the afterdischarges produced by acute hippocampal stimulation. On the assumption that SPECT studies (99mte-ECD) provide indirect evidence of focal and regional neuronal inhibition, present work searches for signs of hyper (excitation) or hypoperfusion (inhibition) produced by SAHCS. METHODS: This work was performed on patients under 4 consecutive conditions. 1.-Intact, 2.- After electrode implantation (but before SAHCS) 3.- After SAHCS and 4.- After anterior temporal lobectomy (ATL). RESULTS: It was found after SAHCS, a significant hypoperfusion of the stimulated hippocampus in relation to both, the contralateral hippocampus in the same study and the ipsilateral hippocampus either in the intact and after electrode implantation consecutive studies. In contrast, no significant differences were found in hippocampal perfusion after SAHCS and after ATL. CONCLUSIONS: Hippocampal SPECT hypoperfusion after SAHCS similar to that after ATL suggests a strong physiological inhibitory hippocampal effect produced by inocuous electrical stimulation. Partially supported by CONACYT Mexico, contracts Nums. 348 A930 and 95 785003.