Utility of 3-T FLAIR and 3D short tau inversion recovery MR imaging in the preoperative diagnosis of hippocampal sclerosis: Direct comparison with 1.5-T FLAIR MR imaging

Purpose: To examine the utility of fluid-attenuated inversion recovery (FLAIR) imaging and three-dimensional short tau inversion recovery (3DSTIR) imaging using a 3-Tesla (3-T) magnetic resonance (MR) imager in the preoperative evaluation of hippocampal sclerosis (HS). Methods: Thirteen patients with intractable medial temporal lobe epilepsy who underwent anterior temporal lobectomy with amygdalohippocampectomy were studied. MR images were obtained twice, once with a 1.5-T imager and once with a 3-T imager. The extent of hippocampal resection was determined according to the findings on intraoperative hippocampal electroencephalography. We compared the diagnostic utility of FLAIR for HS between 1.5-T and 3-T MR imaging. In addition, the relationship between the existence of hypointense areas in the hippocampus (HIAs) on 3DSTIR and the severity of HS pathology (as evaluated using Watson's grading) was examined. The relationship between postoperative seizure outcome and postoperatively remaining HIAs was also evaluated. Results: There was no difference between FLAIR images from 1.5-T and 3-T imaging in the detection of HS. With 3DSTIR, an HIA in unilateral hippocampus was observed in all of the nine cases exhibiting severe pathologic HS (Watson's grade III-V). In seven cases with HIA, the extent of hippocampal resection was smaller than the HIAs. Every case showed good seizure outcome (Engel's class I and II). Discussion: In the diagnosis of HS, no substantial difference was noted between 1.5-T and 3-T MR imaging. However, 3DSTIR using 3-T MR imaging is useful for evaluating the extent of HS, although postoperative HS remnants are not correlated with surgical outcomes.