PhD Student University College London, London, United Kingdom London, England, United Kingdom
Rationale: Anterior temporal lobe resection (ATLR) in the speech-dominant hemisphere can lead to language decline in 30-50% of patients, despite typically not resecting language-associated cortical areas. Deficits have been shown to arise when white matter (WM) is compromised (1). As that study only examined WM properties preoperatively, we here investigated if intra-operative dissection of language-related fiber bundles was associated with language decline. Methods: Using 32 patients with left temporal lobe epilepsy, left-sided language dominance based on verbal fluency functional MRI (fMRI) who had undergone ATLR. Using diffusion MRI-based data we modified an automated tractography method (2) to reflect current literature and to reconstruct the arcuate (AF) and inferior fronto-occipital fasciculus (IFOF). Resection masks were manually drawn based on pre-/post-operative 3D-T1 scans. The percentage of tracts resected were weighted with language lateralization values from the pre-operative verbal fluency fMRI scan to emphasize heavily-ipsilateral language dependence. Language function was measured using a standardized graded naming test (GNT) and semantic fluency test before and three months post-surgery, with factors contributing to post-operative language decline assessed using stepwise linear regression. Results: Resection volume predicted GNT decline (F(1,31)=4.71, p=0.038, R2=.132), but not semantic fluency (F(1,31)=1.82, p=0.187, R2=0.055). Semantic fluency decline was best predicted by resection in two components of the AF terminating in the temporal lobe: pars triangularis and ventral precentral gyrus (F(2,27)=14.86, p< 0.001, adjusted R2=.489); with the best individual predictive component being connections from pars triangularis (F(1,28)=9.18, p=0.005, R2=.497). Here, three subjects yielded inadequate AF reconstruction. GNT decline was predicted by resection of IFOF connections from the superior frontal gyrus medial segment to the occipital/parietal lobe (F(1,23)=4.87, p=0.038, R2=.418); eight subjects yielded inadequate tracts. Conclusions: Our findings demonstrate that language decline could be the result of white matter fiber damage to the IFOF (Figure 1) and anterior extensions of the AF in the temporal lobe (Figure 2). Both the IFOF and resection volume being predictive of GNT could suggest that larger resections include resection of IFOF thus leads to naming decline. Future work will consider a more in-depth analysis of cortical termination areas of these bundles and include other language-related fiber bundles to refine surgical approaches to minimize language decline. References [1] Kaestner, E., Balachandra, A. R., Bahrami, N., et al. The white matter connectome as an individualized biomarker of language impairment in temporal lobe epilepsy. NeuroImage: Clinical, 25(102125):1-11,2020 [2] Mancini, M., Vos, S. B., Vakharia, V. N., et al. Automated fiber tract reconstruction for surgery planning: Extensive validation in language-related white matter tracts. NeuroImage: Clinical, 23(101883):1-9,2019 Funding: Please list any funding that was received in support of this abstract.: This work was supported by Epilepsy Research UK (grant number P1904). Click here to view image/table
