ABSTRACT

The goal of this study was to investigate the frequency of hippocampal shape, position, and orientation anomalies in epilepsy patients and healthy controls. In addition, its relationship to seizure semiology, electroencephalographic findings, and other associated imaging findings were analyzed.

A retrospective investigation through our hospital electronic records was performed. In all, 1040 patients with temporal or extratemporal epilepsy and 300 individuals for whom diagnostic magnetic resonance imaging was performed for conditions other than epilepsy were included in the study. Hippocampal shape, position, and orientation abnormalities were classified into 3 major types.

Hippocampal malformation (HM) was found in 168 of the1040 in the patient group. In the control group, HM was detected in 47 of 300 cases. The most common type of HM was type 1 at 60%, followed by type 3 at 38% and type 2 at 22%. HM was observed on the left side in 50% of the cases, it was bilateral in 43%, and it was found on the right side in 7%. Evaluation revealed malformation of cortical development in 34 cases in the patient group and corpus callosum dysgenesis in 38 cases.

HM is not uncommon in non-epileptic individuals. There was no significant correlation between the laterality of the HM and the laterality of the temporal lob epilepsy. Type 3 HM is usually associated with developmental brain anomalies.

Keywords: Epilepsy, hippocampal formation, temporal lobe epilepsy