Abstracts

Rationale: Temporal lobe epilepsy (TLE) has been demonstrated to be associated with extensive anatomical abnormalities (involving both temporal and extratemporal grey and white matter) as well as extensive neuropsychological deficits. The structural basis for the observed neuropsychological deficits (in particular the role of white matter abnormalities in functional deficits) remains poorly understood. The purpose of this study was to use diffusion tensor imaging (DTI) to investigate the relationship between the integrity of cerebral white matter and neuropsychological function in TLE patients. Methods: Twenty-two TLE patients, including eight non-lesional patients and fourteen with unilateral mesial temporal sclerosis, were studied. DTI, FLAIR DTI, and hippocampal T2 relaxometry data were obtained using a 1.5T scanner. Spearman s correlations were performed between fractional anisotropy (FA) of the bilateral fornix, cingulum, external capsule, uncinate fasciculus, as well as the genu and splenium of the corpus callosum, and hippocampal T2 versus neuropsychological tests of verbal and nonverbal memory along with more global measures (such as IQ). Results: The most striking correlations were observed for the left fornix, demonstrating significance with measures of both verbal and non-verbal memory (Recognition Memory for Words: r = 0.538; p = 0.012, and Continuous Visual Memory Test: r = 0.519; p = 0.013) as well as more general cognitive scores (Full Scale IQ: r = 0.615; p = 0.004, Performance IQ: r = 0.611; p = 0.003, and Processing Speed Index: r = 0.668; p = 0.001). Significant associations were also observed between left hippocampal T2 and verbal memory tests (Recognition Memory for Words: r = -0.452; p = 0.040, and Auditory-Verbal Learning Test: r = -0.561; p = 0.007). Other significant correlations include the right external capsule and genu with the Controlled Oral Word Association Test: r = 0.477; p = 0.025, and r = 0.433; p = 0.040, respectively. FA of the right fornix, left external capsule, bilateral cingulum, uncinate fasciculus, and splenium failed to correlate significantly with any of the neuropsychological tests. Conclusions: Our findings suggest that integrity of the left fornix specifically is an important anatomical correlate of both specific (verbal memory) as well as more global (IQ) cognitive function in TLE patients.