Abstracts

Rationale: Post-surgical naming impairments are common and problematic in epilepsy. This is particularly pronounced in temporal lobe epilepsy (TLE) when surgery is performed in the language dominant hemisphere. Research has defined a broad neuro-anatomical naming circuit but the regions essential for naming performance post-surgery are not fully known. Recently, a basal temporal region centered on the fusiform gyrus has been highlighted as potentially important to post-surgical naming outcomes. Here we investigate the association between integrity of the basal temporal white matter and post-surgical naming decline in TLE.

Methods: We obtained pre-surgical visual (Boston Naming Test; BNT) and auditory (Auditory Naming Test; ANT) naming scores from 51 controls, 47 left-TLE (L-TLE), and 42 right-TLE (R-TLE) patients. Post-surgical naming scores were also available for 20 L-TLE patients following anterior temporal lobectomy (ATL), and were used to calculate reliable change indices (RCI’s) for this subset. Hippocampal volumes were calculated from structural MRI and fractional anisotropy (FA) was calculated from diffusion MRI. FA of the white matter directly beneath the cortex (i.e., superficial WM) in the fusiform and in two fiber tracts associated with naming and the fusiform (inferior longitudinal fasciculus; ILF & inferior frontal occipital fasciculus; IFOF) were obtained. Correlations between each imaging measure and RCI were performed.

Results: Table 1 displays the bi-variate correlations of naming performances with demographic and each imaging variable. Pre-surgically, there was a strong positive relationship between both visual and auditory naming with the bilateral ILF and IFOF. In addition, education was positively correlated with naming performances. Hippocampal volume was positively correlated with visual naming but not auditory naming. For the fusiform, left but not right superficial WM was positively correlated with visual and auditory naming scores.

Post-surgically, higher pre-operative naming score and higher left hippocampal volume were both risk factors for visual naming decline after left ATL. For white matter tracts, higher white matter FA pre-surgically was associated with better outcomes post-surgically. This was most consistent in the ILF, which was significant for visual naming. The association with auditory naming approached significance. For the fusiform, higher superficial WM FA on the contralateral side was associated with better naming outcomes. Figure 1 provides scatterplots of the associations between the ILF and right fusiform and visual and auditory naming RCIs.

Conclusions: Higher bilateral basal temporal white matter integrity is associated with better visual and auditory naming ability pre-surgically and may be a protective factor against post-operative naming decline. In particular, integrity of the right fusiform WM may act as a reserve for naming abilities following left ATL. This suggests that contralateral basal temporal WM networks may be important to naming preservation following ATL.

Funding: Please list any funding that was received in support of this abstract.: R01 NS065838 to C.R.M., T32 MH018399 to E.K.