Alumina cream-induced focal motor seizures in cats. V. Unilateral lesions of the brain-stem reticular formation.

The effect of unilateral mesencephalic (MRF) and pontine (PRF) lesions on EEG-EMG patterns of type B and C alumina cream induced focal motor seizures was studied on cats with chronically implanted electrode and cannula lesion systems. EEG patterns included number, amplitude and contralateral propagation of type B spikes and occurrence and duration of type C tonic-clonic discharges. EMG patterns included changes in muscular multiple unit activity (EMG-MUA) time locked to the onset of type B spikes and to the onset (tonic OTCD) and the end (clonic ETCD) of type C tonic-clonic EEG paroxysmal discharges. (1) MRF lesions ipsilateral to the cortical epileptogenic focus significantly increased number, amplitude and propagation of type B EEG spikes and the occurrence, but not the duration, of type C EEG tonic-clonic discharges. They also reduced amplitude of type B muscular jerks and blocked type C tonic contradversion with a significant decrease in EMG-MUA time locked to the onset of type B spikes and type C paroxysmal EEG discharges. (2) PRF lesions contralateral to the cortical epileptogenic focus produced an effect on muscular contractions of type B and C seizures similar to that produced by ipsilateral MRF lesions. PRF lesions, however, did not significantly change the EEG patterns of type B and C seizures. (3) Neither MRF lesions contralateral nor PRF lesions ipsilateral to the cortical epileptogenic focus produced significant changes on EEG and EMG patterns of types B and C epileptic seizures.