Temporal lobe epilepsy due to hippocampal sclerosis in pediatric candidates for epilepsy surgery

Objective: To characterize the clinical, EEG, MRI, and histopathologic feat ures and explore seizure outcome in pediatric candidates for epilepsy surge ry who have temporal lobe epilepsy (TLE) caused by hippocampal sclerosis (H S). Methods: The authors studied 17 children (4 to 12 years of age) and 17 adolescents (13 to 20 years of age) who had anteromesial temporal resection between 1990 and 1998. Results: All patients had seizures characterized by decreased awareness and responsiveness. Automatisms were typically mild to moderate in children and moderate to marked in adolescents. Among adolesce nts, interictal spikes were almost exclusively unilateral anterior temporal , as opposed to children in whom anterior temporal spikes were associated w ith mid/posterior temporal, bilateral temporal, extratemporal, or generaliz ed spikes in 60% of cases. MRI showed hippocampal sclerosis on the side of EEG seizure onset in all patients. Fifty-four percent of children and 56% o f adolescents had significant asymmetry of total hippocampal volumes, where as the remaining patients had only focal atrophy of the hippocampal head or body. Subtle MRI abnormalities of ipsilateral temporal neocortex were seen in all children and 60% of adolescents studied with FLAIR images. On histo pathology, there was an unexpectedly high frequency of dual pathology with mild to moderate cortical dysplasia as well as HS, seen in 79% of children and adolescents. Seventy-eight percent of patients were free of seizures at follow-up (mean, 2.6 years). A tendency for lower seizure-free outcome was observed in patients with bilateral temporal interictal sharp waves or bil ateral HS on MRI. The presence of dual pathology did not portend poor posts urgical outcome. Conclusions: TLE caused by HS similar to those in adults w ere seen in children as young as 4 years of age. Focal hippocampal atrophy seen on MRI often was not reflected in total hippocampal volumetry. Childre n may have an especially high frequency of dual pathology, with mild to mod erate cortical dysplasia as well as HS, and MRI usually, but not always, pr edicts this finding. Postsurgical seizure outcome is similar to that in adu lt series.