Comparative diagnostic utility of 1H MRS and DWI in evaluation of temporal lobe epilepsy

Objective: To compare the ability of diffusion-weighted MRI (DWI) and H-1 MRS to lateralize to the temporal lobe of seizure onset and to predict postoperative seizure control in patients with temporal lobe epilepsy (TLE). Methods: Forty TLE patients who subsequently underwent epilepsy surgery and 20 normal subjects were studied with H-1 MRS and DWI. Medial parietal and temporal lobe N-acetylaspartate (NAA)/creatine (Cr) ratios and hippocampal and temporal stem apparent diffusion coefficients (ADC) were obtained. Lateralization to either temporal lobe with each MR measurement was based on the threshold values derived from +/-1-SD right/left ratios of normal subjects. Results: Temporal lobe NAA/Cr lateralized to the operated temporal lobe in 18 of 40 (45%), hippocampal ADC in 32 of 40 (80%), and temporal stem ADC in 26 of 40 (65%) patients. Almost all of the cases that lateralized to the surgical side with NAA/Cr ratios (94%) had an excellent postoperative seizure control (p=0.01). Lateralization to the side of surgery was not associated with surgical outcome with hippocampal and temporal stem ADC (p>0.05). Conclusion: H-1 MRS and DWI complement each other in the clinical setting. DWI more frequently lateralized to the operated side, and H-1 MRS was a better predictor of postoperative seizure control.