Abstracts

Diffusion analysis can be useful to detect ultrastructural brain changes. This technique has been used to study hippocampal sclerosis, and its utility has been compared with MR spectroscopy (MRS). It is considered that diffusion can give an independent measure of hyppocampal abnormalities. Comparison of lateralizing abnormalities using diffusion with high b-values and with multivoxel spectroscopy may be of clinican relevance, in order to identify situations for which each technique provide more acurate information. Our work describes the technique of hippocampal analysis with diffusion, analyzes different diffusion patterns in healthy subjects and patients with mesial temporal sclerosis (MTS) using different b-values, and correlates findings in diffusion with multivoxel MRS. Thirty healthy volunteers were compared with 30 patients with clinical, electroencephalography, and MR imaging consistent with MTS using a 3 T MR unit. Values of diffusion studies were obtained using a b-value of 1000 and 3000 at the head and body of the hippocampus. Multivoxel MRS was performed and NAA/Cr values obtained in the same locations were correlated with diffusion values. No technical difficulties were found during the procedure of diffusion studies. Concerning apparent diffusion coefficients (ADC), there was mild intersubject variability, and less than 3% difference between each side in healthy subjects. In MTS side to side differences in ADC were above 10%, and were more pronounced when higher b-values were used. The head of the hippocampus had higher differences in diffusion studies than the body. MR spectroscopy had higher technical difficulties, due to poor shimming, most notably at the head of the hippocampus, where MRS could not be interpreted, both in healthy volunteers as well as in patients. There was adequate correlation between diffusion and MRS. There is adequate concordance between diffusion and MR imaging in patients with distinct signs of MTS. However, the correlation in patients with less clear signs of MTS should be investigated. There is also good correlation between diffusion and MRS, but the sensibility of diffusion is superior to MRS at the head of the hippocampus, where pathology is more common in MTS. Considering this difference, diffusion may be a complementary tool to MRS.