Effect of sagittal transections of the brain stem tegmentum on alumina cream-induced focal motor seizures in cats.

The effect of extensive and circumscribed sagittal transections of the brain stem tegmentum on types B (epilepsia partialis continua) and C (contradversive tonic-clonic seizures) alumina cream-induced focal motor seizures in cats was investigated. The neurological abnormalities of cats with transections and differences in the EEG-EMG patterns of types B and C seizures between operated and intact animals were statistically analyzed. Animals with either extensive or superior central nucleus transections showed bilateral neglect and internuclear palsy syndromes, no tonic type C seizures (contradversion), and a significant decrease in electromyogram multiple-unit activity (EMG MUA) from 0 to 10 s or more after the onset of EEG paroxysmal tonic-clonic discharges. Animals with rostral transections showed a unilateral neglect and internuclear palsy or ataxic syndromes with a concomitant partial reduction of contradversive seizures and a significant decrease in EMG MUA from 0 to 5 s or less after the onset of EEG tonic-clonic discharges; those with dorsal and caudal transections showed a transient neglect and insomniac syndromes with no differences in contradversion and EMG MUA at the onset of EEG tonic-clonic discharges in relation to intacts. Experimental and intact animals showed neither differences in types C and B EEG patterns nor in EMG MUA at the end of type C EEG tonic-clonic discharges and type B EEG spikes. These results support the idea that tonic and clonic muscular seizures are due to epileptic impulses originating in the cerebral cortex and mediated at the level of the brain stem by different pathways.