Development of perifocal edema in experimental epilepsy induced by cobalt-gelatin.

Two blood-borne tracers, Evans-blue albumin (EBA) and colloidal-iron (Ferrlecit) were applied to visualize the development of perifocal edema in experimental epilepsy induced by cobalt-gelatin (Co-gelatin). This model is known to produce central necrosis with gliomesenchymal scar and peripheral transitory zone in the brain cortex. Characteristic red fluorescence of EBA was detected diffusely in the necrotic area surrounding the Co-gelatin implant and EBA labelled individual neurons reflecting cell membrane injury in the transitory zone. The colloidal iron tracer was localized mainly in the gliomesenchymal scar. It is proposed that neurons with altered membrane permeability to EBA in the transitory zone may play a role in the genesis of epileptic spike activity. The marked labelling of the gliomesenchymal scar by colloidal-iron indicates furthermore that this newly vascularized tissue with leaky capillaries may be a source of perifocal edema.