Study of the hippocampal internal architecture in temporal lobe epilepsy using 7 T and 3 T MRI

To compare the hippocampal internal architecture (HIA) between 3 and 7 Tesla (T) magnetic resonance imaging (MRI) in patients with temporal lobe epilepsy (TLE), and to investigate the relationship between HIA and hippocampal volume, and postoperative outcomes.

Thirty-nine TLE patients were recruited with 3 and 7 T MRI scans and a semi-quantitative assessment of the HIA was performed. Differences in HIA scores between 3 and 7 T MRI were evaluated. HIA and hippocampal volume asymmetry were also calculated and compared. The utility of HIA and hippocampal volume asymmetry in epilepsy lateralization, and the predictive value between these two indicators were compared. The relationship between HIA and postoperative outcomes was investigated in 25 patients with amygdalohippocampectomy.

HIA scores of epileptogenic hippocampi were lower than those of non-epileptogenic hippocampi at 3 and 7 T MRI. Higher HIA scores were observed at 7 T MRI. The HIA asymmetry and hippocampal volume asymmetry were both strong predictors for epilepsy lateralization and did not show difference in predictive value. No statistical differences in HIA asymmetry were observed between seizure-free patients (ILAE 1) compared to patients with seizures (ILAE 2-5).

Visualization of hippocampal internal architecture (HIA) may be improved at 7 T MRI. HIA asymmetry is a significant predictor of laterality of seizure onset in TLE patients and has similar predictive value as hippocampal volume asymmetry, however, HIA asymmetry at 7 T does not have extra value in determining epilepsy lateralization and neither does predict surgical outcomes.