Evidence of Secondary Epileptogenesis in Amygdaloid Overkindled Cats: Electroclinical Documentation of Spontaneous Seizures

: Twenty-four spontaneously occurring convulsive seizures were documented by closed-circuit TV (CCTV)-EEG monitoring in 3 cats subjected to unilateral amygdaloid overkindling for < or = 2 years. Electroclinical manifestations suggested that the seizures originated in the kindled amygdala (AM) (10 seizures in 3 cats), contralateral AM (7 seizures in 3 cats), or ipsilateral frontal cortex (7 seizures in 1 cat). All seizures of AM origin except one occurred during sleep 23 h to 20 days after the last stimulation-induced kindled seizure and culminated in secondarily generalized seizures. The seizures of frontal cortical origin occurred during waking within 1 h of a kindled seizure and remained partial in nature. In seizures of AM origin, ictal patterns at the primary and secondary sites were mirror images of each other, but latency of onset of each seizure stage in seizures of secondary site AM origin was longer than that in seizures of primary site AM origin in 2 of the 3 animals. We conclude that the secondary epileptogenic functional alterations capable of producing clinical seizures do occur in AM-overkindled cats, but the seizures are not entirely independent of the primary kindled site.