Hippocampal synaptic pathology in patients with temporal lobe epilepsy

Immunostaining of synaptic terminals was studied in the hippocampus of 26 patients who had surgical resections for intractable temporal lobe epilepsy. Two monoclonal antibodies (EP10 and SP12) reactive with distinct synaptic antigens were used on paraffin-embedded tissues. The results indicated qualitative reductions on synaptic terminals in CA4 and other regions where cell loss is reported. The inner molecular layer of the dentate gyrus was observed to have increased synaptic immunostaining. Synaptic terminal loss in CA4 and redistribution in the molecular layer were most frequent in cases with hippocampal sclerosis. However, both forms of synaptic pathology were also noted in most cases where the pathological findings were classified as indefinite, and in some cases associated with mass lesions of the temporal lobe. These results support the importance of neuronal loss and synaptic reorganization as possible mechanisms of illness in epilepsy. They also indicate that synaptic immunostaining may be a useful adjunct to routine neuropathological diagnostic techniques.