Abstracts

Rationale: Temporal lobe epilepsy (TLE) patients suffer pervasive effects on social cognition, particularly the ability to recognize subtle cues of anxiety in others. The superior temporal gyrus (STG) has been implicated in the processing of social stimuli. Furthermore volumetric differences in right STG structure have been described in autism, a neurodevelopmental disorder with prominent deficits in social cognition. Structural abnormalities of the right STG therefore might be associated with measurements of social cognition in TLE patients. Voxel-based morphometry (VBM) has been used to describe a complex relationship between clinical measures of anxiety and brain structure in healthy adults; there appears to be an inverse relationship in the right frontal lobe, cingulate and left temporal lobe, and a positive relationship in the left and right inferior frontal gyri. We sought to examine this relationship in TLE patients, hypothesizing a relationship between right STG volume and measures of anxiety. Methods: We explored the relationship between the anxiety sub-score from The Awareness of Social Inference Test (TASIT) and right STG volume in 17 TLE patients using an optimized VBM procedure. Subjects underwent 1.5T MRI brain scanning as part of epilepsy surgery evaluation. The MRI data were converted to DICOM format then underwent spatial normalization to a standard stereotactic atlas. The images were modulated to reflect local brain volume, followed by smoothing with an 8mm Gaussian kernel. The relationship between regional brain volume and the anxiety sub-score was assessed using SPM5, limiting the search region to the right STG. Voxels surviving this analysis with a p-value of less than 0.001 were considered significant. Results: We found an inverse relationship between anxiety sub-scores and a 116-voxel cluster of gray matter volume in the right STG. We found no positive relationship between anxiety scores and brain structure. Conclusions: Our findings of an inverse relationship between measures of anxiety and brain structure in the right STG in TLE patients is new and contrast findings reported in normal adults. The etiology of impaired social cognition in TLE is not clear but out results suggests a structural basis for this observation.