Hippocampal sclerosis revisited

Studies dating back more than 150 years reported a relationship between hip pocampal sclerosis and epilepsy. Retrospective studies of patients who unde rwent temporal lobectomy for intractable partial epilepsy found a relations hip between a history of early childhood convulsions, hippocampal sclerosis , and the development of temporal lobe epilepsy. Many believe that febrile seizures lead to hippocampal damage and this in turn predisposes the patien t to the development of temporal lobe epilepsy. Studies in adult rats have shown that seizures can lead to hippocampal damage and unprovoked recurrent seizures. However, many questions remain as to the relevance of early chil dhood seizures to hippocampal sclerosis and temporal lobe epilepsy. Human p rospective epidemiologic studies have not shown a relationship between earl y childhood seizures and temporal lobe epilepsy. Recent MRI studies in huma ns suggest that a preexisting hippocampal lesion may predispose infants to experience febrile seizures, later on hippocampal sclerosis, and possibly t emporal lobe epilepsy may occur. Unlike the studies in adult rats, normal i mmature rats with seizures have not been shown to develop hippocampal damag e or unprovoked seizures in adulthood. Furthermore, animal studies reveal t hat preexisting brain abnormalities can predispose to hippocampal damage fo llowing seizures early in life. This paper reviews evidence for and against the view that early childhood convulsions, hippocampal sclerosis, and temp oral lobe epilepsy are related, while also exploring clinical and animal st udies on how seizures can lead to hippocampal damage, and how this can resu lt in temporal lobe epilepsy. By better understanding the cause and effect relationship between early childhood seizures and hippocampal injury in nor mal and abnormal brains specific treatments can be developed that target th e pathogenesis of epilepsy. (C) 1998 Elsevier Science B.V. All rights reser ved.