Abstracts

RATIONALE: To determine the ability of the interictal apparent diffusion coefficient to lateralize the lesion in patients with hippocampal sclerosis. METHODS: Five healthy volunteers and 9 patients with medial temporal lobe epilepsy having unilateral hippocampal sclerosis were prospectively examined with interictal MR diffusion-weighted imaging (DWI). Diagnosis of hippocampal sclerosis was based on the presence of unilateral atrophy and/or high T2 signal of the hippocampus. DWI was performed on a 1.5 T (GE Echospeed) using SE EPI with variable diffusion gradients (b=0, 500,1000 s/mm2, TR/TE = 6500/103 ms). ADCs were obtained from both hippocampal areas and temporal lobes bilaterally. The capability of DWI and ADC to lateralize the lesion was evaluated by visual assessment and calculated ADC values with conventional MRI diagnosis being used as a standard of reference. RESULTS: In all patients, visual assessment of DWI failed to lateralize the lesion. However, the mean ADC values measured at both hippocampal areas and temporal lobes were significantly higher on the lesion side than on the contralateral side (p<.05). The overall correct lateralization rate of interictal ADC was 100% (9/9). In healthy volunteers, there was no significant difference in DWI and ADC between both sides. CONCLUSIONS: Interictal ADC may be used as a sensitive diagnostic method for lateralization of the epileptogenic area in the presurgical evaluation of patients with inconclusive MRI findings of hippocampal sclerosis