FUNCTIONAL MAPPING OF THE EARLY STAGES OF STATUS EPILEPTICUS - A C-142-DEOXYGLUCOSE STUDY IN THE LITHIUM PILOCARPINE MODEL IN RAT

Continuous convulsive activity in status epilepticus generally does no t occur suddenly in response to the inciting epileptogenic agent, but is rather the culmination of a stereotyped sequence of stages. Initial ly seizures are discrete, then undergo waxing-and-waning of convulsive / electroencephalographic severity. Following a transitional EEG-recor ded fast-and-slow spiking phase, continuous fast spiking with invarian t convulsive behavior ensues. We sought to map the seizure anatomic su bstrates corresponding to these stages, utilizing the C-14-2-deoxygluc ose technique, in order to make inferences about underlying mechanisms . The lithium-pilocarpine status epilepticus model in rat was employed . Cerebral autoradiographs associated with discrete seizures revealed non-uniform cerebral metabolic activation, with rostral cortical and o lfactory areas especially involved. Portions of basal ganglia were als o activated, consistent with projections from seizure-activated areas. Successive stages of status entry displayed additional limbic and cor tical activation, along with subcortical projection sites, so that by fast-and-slow spiking most forebrain areas were recruited. Based on th ese results, a model is proposed whereby cyclical seizure-attenuating mechanisms cause, in the initial stages of status entry, fluxing of se izure anatomic extents between small and large cerebral domains, with corresponding cycling of convulsive severity. In the later stages of s tatus entry, these mechanisms become ineffective, resulting in steady- state maximal forebrain recruitment, associated with continuous and in variant convulsive behavior and electrographic fast spiking.