Epilepsy-induced microarchitectural changes in the brain.

Our understanding of the pathogenesis of the neuropathology of epilepsy has been challenged by a need to separate the "lesions" that cause epilepsy from the "lesions" that are produced by the epilepsy. Significant clinical, genetic, pathologic, and experimental studies of Ammon horn sclerosis (AHS) suggest that AHS is the result and cause of seizures. The data support the idea that seizures cause alterations in cell numbers, cell shape, and organization of neuronal circuitry, thus setting up an identifiable seizure-genic focus. As such, AHS represents a slowly progressive lesion and a search for the cause of the initiating seizure has led to the identification of ion channel mutations. In this report, the neuropathology of other conditions associated with intractable epilepsy is considered, suggesting that in them similar epilepsy-produced alterations in microarchitecture can be observed. The idea is important to define the optimum time for epilepsy surgery and the underlying etiology of these seizure-genic lesions.