Abstracts

Rationale: Recently, diffusion tenor image (DTI) is capable of improving detection of structural abnormalities of brain tissues by calculation of microscopic movement of tissue water molecules. Generally, in the irritative brain regions from epileptic condition the mean diffusivity (ADC) is increased and the anisotropy reduced during chronic or interictal period. But, there has been scanty of reports on the acute changes of water diffusion by epileptic seizure. We analyzed the diagnostic efficacy of DTI during early postictal period (within 24hrs) by voxel based morphometry using SPM and compared the diagnostic yield to that of EEG findings and clinical findings.Methods: Fourty one epilepsy patients (male 24, age: 10-88) and 30 age-matched control subjects (age: 23-74, male 13) was selected for analysis. For reflecting the changes by aging process, we divided them into two groups (young<50 years, old>50years, patients and controls respectively). All DTI was performed within 24hours, and fractional anisotropy (FA) and ADC map was calculated by home-made software (DTIcalc) for SPM analysis. The area with increased ADC and decreased FA was compared to the clinical and EEG findings for evaluation of its localizing value.Results: The area of increased ADC was well corresponded with EEG findings in 12 patients (29.3%). In normal conventional MRI group (15/41, 36.6%), 6 patients (40%) shows EEG matched regions of increased ADC. Also, another 5 (12.2%) patients had the DTI findings not correlated with their EEG features, but the areas with increased ADC of them were well corresponded to the presumptive epileptic areas by seizure semiology. Comparing to old groups, young age group showed better diagnostic yield of DTI findings [young vs. old group: EEG abnormality matched to DTI abnormality 11/28 (39.3%) vs. 1/13 (7.7%); DTI findings matched to EEG findings with normal conventional MRI 6/13 (46.2%) vs. 0/2 (0%); DTI findings matched only to clinical semiology 3/28 (10.7%) vs. 2/13(15.4%)] But, it showed little diagnostic value of FA measurement of DTI (positive result in only one patient in all patients). Conclusions: By SPM analysis, we can detect the acute change of water diffusivity with early postictal DTI in epileptic patients and it has a considerable correlation with the EEG or clinical findings. We can assume that early postictal DTI analysis may be used as a complementary tool to diagnosis of epileptic foci.