Abstracts

Rationale: Corpus callosotomy and modified functional hemispherectomy are surgical procedures for seizure control in pediatric epilepsy patients whom depend upon division of white matter tracts to be effective. Success rate of corpus callosotomy (up to 70%) and functional hemispherectomy (up to 78%) can be improved with intraoperative anatomic 1.5T MRI scan (up to 90%) by identifying residual crossing white matter tracts. To date, the authors are not aware of other studies evaluating the effectiveness of DTI in improving this post surgical outcome. We chose to evaluate intraoperative 3T MRI scans with DTI images for these complicated patients. Methods: Unenhanced MRI's of the brain (n=21) were retrospectively reviewed in 17 pediatric epilepsy patients. Intraoperative MRI's immediately after first resection attempt were obtained in 10 patients receiving corpus callosotomy and 7 patients receiving modified functional hemispherectomy. A total of six patients receiving intraoperative DTI evaluation showed incomplete white matter tract disconnection which prompted immediate second attempt surgery. These patients received subsequent second look intraoperative MRI showing complete disconnection on DTI. All intraoperative MRI scans included axial and coronal T2 weighted images as well as 20 directional DTI. The cases were all scanned on the same intra operative Siemens 3T MR scanner. Two CAQ Pediatric Radiologists and one CAQ Neuroradiologist read all of the scans. Results: 2 out of 10 corpus callosotomy patients had incomplete disconnection of white matter fiber tracts based on DTI images. These patients proceeded to immediate second attempt surgery which showed complete disconnection on subsequent intraoperative DTI. 4 out of 7 modified functional hemispherectomy patients had incomplete disconnection with as little as 2mm of white matter fibers remaining on DTI. All of these patients underwent immediate second surgery for complete fiber disconnection proven on second intraoperative DTI. In summary, 100% of patients (n=6) with incomplete disconnection on first intraoperative DTI proceeded immediately to complete disconnection proven by second intraoperative DTI. Conclusions: Preliminary data suggests that adding DTI sequences (less than 10 minute scan) to intraoperative MRI, may improve outcome in these complicated patients whom depend upon complete disconnection of their white matter tracts for optimal post surgical results.