Abstracts

Rationale: The Cingulum as a part of limbic system has extensive reciprocal connections with mesial temporal lobe and also with extratemporal lobe structures. DTI interrogates white matter integrity and measures the amplitude (diffusivity) and directionality (anisotropy) of diffusional motion. We previously analyzed DTI characteristics of the cingulum in refractory TLE and showed that unilateral seizures have a detrimental effect on the bilateral cingulum in different parts, consistent with chronic Wallerian degeneration. We investigated the relationship between DTI measures and neuropsychological findings in patients with right and left TLE. Methods: We retrospectively analyzed DTI images of the cingulum in 28 patients with unilateral refractory TLE (18 left, 10 right). Patients with lesions other than mesial temporal sclerosis were excluded. Diffusion images were analyzed by using “DTI-studio” (Jiang et al. 2006) computer program. ROIs (2x2 rectangular pixels, 1 pixel=0.94 x 0.94 x 4mm3) were chosen in 3 subregions of the cingulum; 1 ROI in anterior, 4 ROIs in superior and 2 ROIs in descending part. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial and perpendicular diffusivities were measured for each ROI, and computed as an average value per cingular subregion. All patients completed a neuropsychological battery as part of their preoperative investigations that included measures of executive functioning and memory. Spearman correlations between DTI and cognitive measures were examined and considered significant if p < .05. Results: In LTLE, the average FA and perpendicular diffusivity in the superior part of the ipsilateral cingulum were significantly correlated (positive and negative correlation respectively) with all memory measures, both visual and verbal. There were also significant negative correlations between the average ADC of the superior part of the contralateral cingulum and the measure of problem solving. In RTLE, the ipsilateral cingulum indices did not correlate with any of the cognitive measures. However, the average ADC values of the contrlateral cingulum desc part revealed significant negative correlations with several measures of executive functioning, including verbal fluency, figural fluency, abstract verbal reasoning and nonverbal reasoning. Conclusions: The results suggest that DTI findings of cingulum correlate with cognitive performance on measures of memory and executive functioning, although this relationship is rather complex. This could be explained by the fact that the cingulum has extensive reciprocal connections with both temporal and frontal lobes. It is notable that in left TLE significant correlations are found between DTI measures in the left superior cingulum and measures of temporal lobe function, whereas in right TLE, DTI measures in the descending part of the left cingulum related to frontal lobe function. Future studies with larger sample sizes are needed to confirm these findings.