Hippocampal Malrotation: Is It Epileptogenic?

Hippocampal malrotation (HIMAL) is an anatomical phenomenon appearing as incomplete rotation of the hippocampus in the course of ontogenesis. The relationship between HIMAL and epilepsy is unclear. We analyzed clinical observations of 25 patients (13 female/12 male, mean age 11.38±4.71 years) with HIMAL but without other brain anomalies. Brain MRI data and EEG recordings of 19 patients (76%) were considered. In the examined group, HIMAL was left-sided in 21 (84%), right-sided in 2 (8%), and bilateral in 2 of the patients (8%) as well. In 20 patients (80%), convulsions were manifested. A normal EEG pattern was found in 7 subjects (38%), whereas in 12 patients (62%) the pattern was abnormal. Seizures were observed in all patients with left-sided HIMAL, but only 1 patient demonstrated spike-and-wave activity on the side of malrotation. Our results do not support a strictly direct causative role for HIMAL in the pathogenesis of childhood temporal lobe epilepsy, but this developmental brain abnormality should be considered a significant factor promoting such a pathological condition.