FREQUENCY OF UNILATERAL AND BILATERAL MESIAL TEMPORAL SCLEROSIS IN PRIMARY AND SECONDARY EPILEPSY - A FORENSIC AUTOPSY STUDY

Controversy exists regarding the pathogenetic relationship of mesial t emporal sclerosis (MTS) to epileptogenesis. Some investigators view hi ppocampal sclerosis as the primary cause of temporal lobe epilepsy, wh ereas others interpret the changes to be the result of chronic seizure activity. The present autopsy-based study attempts to clarify the eti ologic relationship between mesial temporal sclerosis and epilepsy. To investigate the assumption that bilateral MTS is more likely to be th e result of chronic seizure activity associated with a seizure focus o utside the hippocampus, two subject groups were identified. The first group comprised 43 patients who had no extrahippocampal pathology and were classified as having primary epilepsy. The second group comprised 35 patients who, had identifiable extrahippocampal pathology and were classified as having secondary epilepsy. Fifteen of the 35 cases of s econdary epilepsy also had MTS; seven of these were unilateral and eig ht were bilateral. Of the 43 cases with primary epilepsy, only one had MTS, and it was unilateral. Significantly more cases of primary epile psy than secondary epilepsy had no MTS (p < 0.001), suggesting that bo th unilateral and bilateral forms of MTS occur with greater frequency in subjects with seizure foci outside the hippocampus. These results a lso suggest that unilaterality of MTS does not exclude an extrahippoca mpal cause.