Onset-age dependent MRI based hippocampal volume asymmetries in intractable partial complex temporal lobe epilepsy

The purpose of this study was to determine whether the age at onset of temporal lobe epilepsy influences hippocampal volume. Fifteen right-handed patients with medically intractable partial complex epilepsy of temporal origin were studied in quantified magnetic resonance imaging (MRI) and neuropsychological tests. In seven patients (mean age: 24 years) epilepsy began before the age of three (? YOUNG), in eight patients (mean age: 29 y) after the age of three (= OLDER). Education, social integration, duration of epilepsy and seizure frequency were equal in YOUNG and OLDER. The mean hippocampal volume, after normalization to total intracranial volume was for the right and for the left side smaller in YOUNG than in OLDER (p ≤ 0.02). The side-to-side asymmetry of absolute hippocampal volume was in patients with left-side focus more pronounced in YOUNG than in OLDER (p < 0.03). The number of patients with right-side focus was too small for statistical analysis. Results of neuropsychological testing showed no significant differences between YOUNG and OLDER. Onset-age of epilepsy before three years is associated with a higher risk of bilateral hippocampal hypotrophy and unilateral hippocampal asymmetry. Performance in neuropsychological testing seems not to be significantly influenced by hippocampal volume or age at onset.