HIPPOCAMPAL VOLUMETRIC AND MORPHOMETRIC STUDIES IN FRONTAL AND TEMPORAL LOBE EPILEPSY

TLDR

Ammons Horn sclerosis is the most common temporal lobe pathology, and existing imaging techniques vary in their success at detecting it. This study applies a three‑dimensional MRI volume technique to measure total hippocampal volume and assess symmetry. Using 1.5‑mm contiguous images on a GE IC workstation, the authors calculated hippocampal surface area and total volume, graphically displaying cross‑sectional area to evaluate focal atrophy along the hippocampus. In 20 TLE patients, asymmetric hippocampal volume loss was observed in all cases—predominantly anterior in 12, posterior in 1, and widespread in 7—while no loss appeared in controls or 20 FLE patients, and widespread loss correlated with secondary generalized seizures, demonstrating the method’s ability to distinguish hippocampal from frontal pathology.

Abstract

The most common temporal lobe pathology is Ammons Horn sclerosis (AHS), and several different imaging techniques have been utilized to detect this with varying success We describe the clinical application of magnetic resonance imaging (MRI) using a three-dimensional volume technique which allows total hippocampal volume to be measured and symmetry evaluated. Hippocampal surface area was calculated in sequential 1.5 mm thick contiguous images, using a GE IC workstation. Total volumes and surface areas were calculated. The cross-sectional surface area at 1 5 mm intervals was displayed graphically, permitting morphometric analysis of the hippocampus throughout its length. Focal atrophy within any part of the hippocampal formation (HF) and its extent could thus be assessed. Patients with well-lateralized temporal lobe epilepsy (TLE) (n = 20) and well-defined frontal lobe epilepsy (FLE) (n = 20) were studied, and volumes compared with normal values derived from 10 neurologically normal controls Asymmetric hippocampal volume loss was demonstrated in all 20 patients with clinically typed TLE, but not in normal controls or patients with FLE. Volume loss distribution was anterior in 12 patients, posterior in one patient and widespread in seven patients. Secondarily generalized seizures were strongly associated with widespread loss. This method of surface area and volumetric analysis of the hippocampus in TLE can demonstrate asymmetry and focal involvement, and help distinguish between hippocampal and frontal pathologies