HIPPOCAMPAL DEVELOPMENTAL-CHANGES IN PATIENTS WITH PARTIAL EPILEPSY -MAGNETIC-RESONANCE-IMAGING AND CLINICAL ASPECTS

Developmental disorders of the hippocampal formation (HF) have been de scribed in epileptic syndromes associated with lissencephaly, but HF m alformations can be found without widespread cortical changes. We repo rt 19 patients with partial epilepsy and abnormal HF patterns on magne tic resonance imaging (MRI). The changes consisted of incomplete foldi ng with abnormal medial location along the choroid fissure, globular s hape and/or verticalization, and were observed ed in the following thr ee contexts: (1) diffuse disorder of neuronal migration (n = 1); (2) t emporal lobe malformation (n = 5), including heterotopia, abnormal gyr ation, and, in 2 cases, reduced HF volume; and (3) apparently isolated HF changes (n = 13, bilateral in 3 cases). The clinical features were heterogeneous in terms of severity of epilepsy and, when the focus co uld be determined, in localization (temporal or extratemporal). In 4 p atients with apparently isolated HF changes, MRI was suggestive of bot h abnormal development and hippocampal sclerosis. In these patients, p resurgical investigation and postoperative results suggested multiple epileptogenic foci, involving the frontal lobes in 2 cases. One HF spe cimen was large enough for the observation of developmental abnormalit ies corresponding to the changes seen on MRI. HF changes in shape and/ or position should be included among the structural abnormalities asso ciated with partial epilepsies. They may represent the visible part of a more extensive or more distant disorder of brain development.