Developmental abnormalities of the medial temporal lobe in patients with temporal lobe epilepsy.

PURPOSE To evaluate MR temporal lobe malformations and their frequency in patients with temporal lobe epilepsy. METHODS Two hundred twenty-two consecutive adult patients with temporal lobe epilepsy of varying severity were investigated with 1.0-T or 1.5-T MR units using three-dimensional T1-weighted acquisition protocol. RESULTS Sixteen patients (7.2%) presented with malformations of the temporal lobe. Four patterns of malformations were encountered: (a) heterotopia (n = 1), lining the temporal horn of the lateral ventricle; (b) focal neocortical dysgenesis (n = 6), which consisted of cortical thickening, poor gray/white matter demarcation, abnormal gyration (n = 5), or limited schizencephaly (n = 1); (c) hippocampal malformations (n = 5), which presented as abnormal hippocampal formation associated with a cyst (n = 2), isolated malformation of the subiculum (n = 1), or bilateral hippocampal malformation (n = 2) consisting of an abnormal shape and a misplaced fimbria; (d) complex malformations of the temporal lobe, combining categories a, b, and c (n = 4). The age at onset, severity of the disease, and occurrence of generalized tonicoclonic seizures were not significantly different between patients with malformations and the entire population of patients with temporal lobe epilepsy. CONCLUSION MR analysis of temporal lobe malformations allowed a precise determination of the extent of the malformations and the presence or absence of associated hippocampal disease, all of which are of great help in the preoperative evaluation of patients with intractable epilepsy.