Abstracts

Rationale: Several studies have shown favorable outcomes for temporal lobe epilepsy following anterior temporal lobectomy (ATL); however, few studies have focused on complications and adverse events. Previous studies have demonstrated an overall complication rate between 5.5% and 19% and a rate of major complications between 2.7 and 13.4%. Moreover, symptomatic and asymptomatic visual field defects rates reported in the literature are highly variable ranging from 15% to 100% of patients undergoing temporal lobe resections. In the past decade, stereotactic laser amygdalohippocamectomy (SLAH) has emerged as an alternative for patients who do not wish to undergo or who have contra-indications to craniotomy, or patients with higher risk of cognitive deficits. Rates of seizure freedom following SLAH appear to be slightly lower than after ATL. Conversely, SLAH causes less damage to the lateral temporal neocortex and may be associated with less impact on memory and language function. Changes in white matter integrity after ATL have been demonstrated previously in both ipsilateral and contralateral sides due to Wallerian degeneration. We hypothesized that these changes also occur after SLAH, but on a smaller degree. Thus, our goal was to quantify and compare white matter changes after ATL and SLAH.  Methods: Visual pathways integrity was assessed using diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) in two patients with TLE who underwent ATL or SLAH at two time points preoperative and 6-month postoperative. Whole brain parcellation was performed on T1 weighted images using FreeSurfer. Visual cortex and optic tract labels were extract and registered to DTI images. Deterministic tractrography connecting both regions of interest was performed with TrackGen. Following tract generation, the visual fiber tract was quantified by tract volume and diffusivity measures estimated by DTI (fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD).  Results: Tract volume was decreased after both procedures, with a slightly greater decrease on the ATL patient. FA values were decreased after both procedures, but with a larger difference between both procedures (Table), indicating less integrity of fibers after ATL when compared to SLAH. Changes in MD and AD values were similar between both patients. RD value increased after ATL but remained the same after SLAH, again indicating less integrity of fibers after ATL.  Conclusions: Changes in fiber tract integrity may vary between different procedures for TLE. Our preliminary results suggest that SLAH may be associated with lesser tract degeneration than ATL. However, additional studies with larger samples are necessary to confirm this hypothesis.  Funding: No funding