Abstracts

Rationale: The outcome for temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS) is highly dependent of the correct identification of the unilateral or bilateral sclerotic hippocampus. Although the qualitative MRI analysis for one expert identifies more than 80% of the lesions, quantitative MRI is an important adjuvant for lateralization of the normal MRI TLE patients. Volumetry is one of the most used quantitative MRI (qMRI) techniques but others like relaxometry, and in special magnetization transfer ratio (MTR), are controversial. Our goal is to test the lateralizing ability of MTR, relaxometry and volumetry, both isolated and combined in TLE. Methods: We used the MRI of 32 patients acquired with a 3 T Achieva X-Series (Philips Medical System, Best, The Netherlands). The patients had surgery indicated after evaluation using standardized protocols previously published, and all of them had HS proved by histology. Eighteen had right HS. The hippocampal segmentation was automated using FreeSurfer package and the high-resolution MPRAGE T1-wheighted 3D volume images. Whole brain maps of MTR and T2-relaxometry were computed and the values related to the hippocampus were extracted. The data was analyzed using a discriminant analysis with cross-validation and the normalized difference between hippocampus was also calculated. Results: Individually volumetric measurements on T1-weighted 3D dataset provided accurate lateralization in 30 of 32 patients (94%), MTR in 29 (91%), and T2-relaxometry in 28 (87%). Using the three techniques combined the correct lateralization was achieved in 97% of the patients. Conclusions: Volumetry, MTR and T2-relaxometry are valuable qMRI techniques to improve visual analyses of TLE MRI studies, but the combination of these techniques provides complementary information of hippocampal pathology and represents maximal accuracy for preoperative lateralization.