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

Abstract

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. Materials and methods: 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.Results: 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). Conclusions: 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.

Utility of 7 Tesla Magnetic Resonance Imaging in Patients With Epilepsy: A Systematic Review and Meta-Analysis

“…Qualitative assessment of morphologic characteristics on structural MRI protocols was performed for 16 studies (64%), of which a scoring system was assessed in 7 studies and the detection rate was assessed in 9 studies. In all studies with a scoring system (19)(20)(21)(22)(23)(24)(25), 7T MRI scored higher than 3T MRI for lesion conspicuity of morphologic characteristics and/or reader's confidence (21). The inter-rater agreement of the diagnostic confidence scale was higher on 7T (92.3%) than on 3T (57.7%) (21).…”

Imaging in medically refractory epilepsy at 3 Tesla: a 13-year tertiary adult epilepsy center experience

“…Clinically, MRI negative patients with MTS had better chances at a seizure-free outcome when compared with MRI negative FCD patients and pathology negative patients [ 17 ] . MRI findings of MTS range from subtle T2/FLAIR hyperintensity of the hippocampus or flattening of the interdigitations at the superior aspect of the hippocampal head to frank hippocampal volume loss combined with T2/FLAIR hyperintensity [ 27 ] and internal architectural distortion [ 28 ] (Fig. 3 ).…”

Association Between Microstructural Asymmetry of Temporal Lobe White Matter and Memory Decline After Anterior Temporal Lobectomy

“…Positive LI indicates a leftward asymmetry of hippocampal volume or ROI/tract FA (i.e., higher FA within left hemisphere tracts/ROIs suggestive of more preserved WM integrity), whereas negative LI indicates a rightward asymmetry (i.e., higher FA within right hemisphere tracts/ROIs). LIs have been used extensively with hippocampal volumes, 31 presurgical fMRI, 32 and WM asymmetry, 33 and were robust predictors of language and memory decline following ATL. 34 These measures provide a single measure that takes into account both integrity of the ipsilateral MTL network (structural adequacy) as well as integrity or presumed "functionality" of the contralateral MTL network (structural reserve).…”