Absence of temporal lobe epilepsy pathology in dogs with medically intractable epilepsy

Epilepsy is a common neurological problem in dogs. In some dogs, seizures cannot be controlled adequately with anticonvulsant medication. Temporal lobe epilepsy is the most common type of epilepsy in adult humans, it is frequently resistant to anticonvulsant therapy, and it is commonly associated with characteristic neuropathological abnormalities in the hippocampal dentate gyrus. We sought to test the hypothesis that dogs with medically intractable epilepsy have temporal lobe epilepsy. The hippocampi of 6 dogs that were euthanized because of chronic, recurrent seizures were compared with those of 8 nonepileptic controls. In control and epileptic dogs, stereological cell counting showed similar numbers of neurons in the hilus of the dentate gyrus, somatostatin immunoreactivity identified numerous immunopositive neurons in the hilus, and Timm staining showed the normal pattern of granule cell axon projections. These findings demonstrate a lack of hilar neuron loss and granule cell axon reorganization, suggesting that temporal lobe epilepsy is not a common cause of medically intractable epilepsy in dogs.