Restriction of the spread of epileptic discharges in cats by means of Bragg peak, intracranial irradiation

Abstract

Adult male cats with a single epileptic focus receive neon ion Bragg peak radiation at the Bevalac at Lawrence Berkeley Laboratory. Bragg peak radiation is doposited in a thin disc of brain tissue beneath an epileptogenic focus produced with alumina cream. Paroxysmal electroencephalograms (EEGs) from the occipital cortex of cats confirm the bioelectric changes in the pathogenesis of epilepsy. Distant spread of seizure activity occurs when the cells in the cortical focus fire a series of relatively simultaneous spikes at high frequency with sufficient intensity to develop self-sustained discharges in remote brain areas. The development of a “mirror focus” in the EEG records in the contralateral cortex gives a measure of the distances paroxysmal discharges spread. Interhemispheric responses (IHR) that travel from the alumina-treated cortex via the corpus callosum to the contralateral cortex are a second measure of pathways over which paroxysmal discharges spread. In cat studies Bragg peak radiation is positioned beneath the epileptic cortical focus. Various heavy ion doses are employed to test whether an absorbed dose per cat is sufficient to block the transmission of epileptic activity as a function of the post-irradiation time. The relationship between neon ion dose and the post-irradiation time for the loss of IHR is a measure of the physiological dissociation of the epileptic brain tissue from the remainder of the brain. The loss of the “mirror focus” in EEG records agrees with the IHR findings.