Necrosis of hippocampus and piriform lobe in 38 domestic cats with seizures: A retrospective study on clinical and pathologic findings

The clinical records of 38 cats (1985-1995) with a neuropathologically conf irmed diagnosis of necrosis of the hippocampus and occasionally the lobus p iriformis were evaluated retrospectively. There was no sex or breed predisp osition. Most cats were between and 6 years of age (mean age = 35 months) a nd had either generalized or complex-partial seizures of acute onset and ra pid progression. The seizures had a tendency to become recurrent and to pre sent as clusters or even status epilepticus later in the course of the dise ase. Fourteen cats died spontaneously, and 24 were euthanized. Histopatholo gic examination revealed bilateral lesions restricted to the hippocampus an d occasionally the lobus piriformis. The lesions seemed to reflect differen t stages of the disease and consisted of acute neuronal degeneration to com plete malacia. affecting mainly the layer of the large pyramidal cells but sometimes also the neurons of the dentate gyrus and the piriform lobe. The clinical, neuropathologic, and epidemiologic findings suggest that the seiz ures in these cars were triggered by primary structural brain damage, perha ps resulting from exitotoxicity. The cause remains unknown but epidemiologi c analysis suggests an environmental factor, probably a toxin.