Effects of lesions in ventral anterior thalamus on experimental focal epilepsy

Abstract

The effect of stereotaxic lesions of the ventral anterior thalamus, or the adjacent inferior thalamic peduncle, on experimental models of focal cortical epilepsy was studied. Acute epileptic foci in cat sensorimotor cortex were made by injection of tungstic acid gel. Following ipsilateral lesions of ventral anterior thalamus or the adjacent inferior thalamic peduncle in these animals there was a highly significant reduction in electrographic seizure frequency and duration compared to prelesion control periods. Interictal activity at the focus was not altered. The frequency and duration of spontaneous clinical seizures in five rhesus monkeys with chronic alumina cream foci in motor strip was continuously monitored in activity chairs. Both seizure frequency and duration decreased in all animals in the 4-week period after ipsilateral ventral anterior thalamic lesions as compared to the 4-week control period. Sham lesions did not have these effects. The thalamic lesions did not discernably alter behavior or neurologic function in these primates. Thus ventral anterior thalamic lesions decrease seizure frequency and duration in both acute and chronic experimental models of focal cortical epilepsy. These findings indicate that pathways originating in or passing through the ventral anterior thalamus play a role in the generalization of focal cortical seizures. These lesions in ventral anterior thalamus may be useful in the treatment of medically intractable seizures secondary to foci inaccessible to direct excision.