Neuropathology of temporal lobe epilepsy.

One of the most remarkable pathologies of temporal lobe epilepsy is a severe neuronal loss selectively localized in the hippocampus, often termed as the Ammon’s horn sclerosis. It is yet uncertain whether the neuronal loss is preceded or followed by epileptic seizures. Since, however, the sclerosis has been known to occur preferentially in certain hippocampal regions of epilepsy patients, the neuronal damage may be more or less related with neuroanatomical peculiarity of the hippocampus. The hippocampus including their dentate gyrus is a relatively simple laminated structure with restricted afferent fibers and few intrinsic cell types. The hippocampal mossy fiber gives an intrinsic fiber pathway arising from granule cells of the dentate gyrus, projecting with their characteristic large swellings to a terminal field in stratum radiatum of both CA1 and CA3, and terminating on the proximal apical dendrites of large pyramidal neurons. A shorter proximal mossy fiber projection also is present and was used as the clue for identifying hippocampal subfield C A ~ C . ~ It appears likely, in addition, that granule cells occasionally give off a few axon collaterals back into the molecular layer of the dentate gyms.