Lateralizing ability of single-voxel proton MR spectroscopy in hippocampalsclerosis: Comparison with MR imaging and positron emission tomography

BACKGROUND AND PURPOSE: Proton MR spectroscopy (MRS) is still in the early stages in the evaluation of epilepsy, and comparisons with MR imaging and p ositron emission tomography (PET) in the same patients have rarely been doc umented. The purpose of this study was to evaluate the lateralizing ability of single-voxel MRS in comparison with MR imaging and PET in patients with hippocampal sclerosis, METHODS: Thirty-three patients with intractable temporal lobe epilepsy whos e MR imaging diagnosis was unilateral hippocampal sclerosis and who underwe nt anterior temporal lobectomy and had good postsurgical outcome over 1-yea r follow-up were included in the study. MR spectra were obtained from the h ippocampus bilaterally, using the point-resolved spectroscopy sequence. Met abolite ratios of NAA/Cho and NAA/Cr were calculated from the relative peak height measurements. An NAA/Cho ratio of 0.8 or less and an NAA/Cr ratio o f 1.0 or less were regarded as abnormal. The MRS results were compared retr ospectively with those of MR imaging and PET as to the ability to lateraliz e the epileptogenic focus, RESULTS: The sensitivity of MRS and PET (concordance with MR imaging) was 8 5% each in the lateralization of the ipsilateral lesion side. Bilateral abn ormalities were seen in 30% of the patients. False-lateralization rates for MRS and PET were 3% and 6%, respectively. The concordance rate of MRS and PET was 73%, when comparing the results of the ipsilateral lesion side. CONCLUSION: MRS may be used as an adjunct tool in the evaluation of hippoca mpal sclerosis, like PET, although its sensitivity has to be improved and t he clinical significance of bilateral abnormality is still to be determined .