Abstracts

RATIONALE: To evaluate whether immediate postictal diffusion weighted magnetic resonance imaging(DWMRI) can lateralize seizure foci in patients with nonlesional localization-related epilepsy. METHODS:Ictal onset zones were determined by ictal electroencephalography and seizure semiology. DWMRI were checked as soon as possible after seizure onset. Apparent diffusion coefficients of water(ADCw) were measured from both the cortex of the ictal onset zone and the corresponding region of the contralateral hemisphere. We compared the two values in all patients. RESULTS:All 10 patients were nonlesional except for hippocampal sclerosis in conventional MRI(four patients with medial TLE, three with lateral TLE, two with FLE and one with PLE). The mean time interval from seizure to performance of DWMRI was 51 3/4 9 (minutes). On visual inspection of DWMRI, signal changes on the ictal onset zone could be suspected in only one patient. The mean areas of region of interest(ROI) were 321 3/4 288(mm2) ipsilaterally and 305 3/4 268(mm2) contralaterally to the ictal onset zones, which was not significantly different(p= 0.51). The average value of ADCw from the ictal onset zones was not significantly different from that of the contralateral corresponding cortices(963 3/4 126 and 951 3/4 99 (x10-6mm2/sec),respectively, p= 0.84). CONCLUSIONS: In spite of the presence of some anecdotal reports arguing that postictal DWMRI could help localize epileptogenic foci, our result suggest that its role is still limited in this regard. In order to clarify the role of DWMRI in lateralization of epileptogenic foci, some comparison of postical and interictal DWMRI will be helpful.