Surgical control of semichronic epileptic foci in the cat's sensorimotor cortex

The present work was undertaken in order to find out whether delicate subpial incisions can be used to stop the epileptic activity of cortical lesions induced by cobalt oxide. Epileptic foci were produced in cats by epidural application of cobalt oxide powder. The presence of epilepsy was demonstrated a week later in anesthetized cats by injections of a "trigger dose" of pentamethylenetetrazole. Performance of subpial incisions through the focus area immediately abolished all ongoing epileptic activity. Such activity could not be evoked again by subsequent injection of pentamethylenetetrazole trigger doses throughout a 2-week period. The practical implications of this result are discussed. Some theoretical consequences of the similarity between the response of penicillin foci and that of cobalt oxide foci to the application of subpial incisions were evaluated. Finally, an attempt is made to explain the differences between our results and those produced by other investigators who also attempted to inactivate cobalt lesions in the cortex.