Abstracts

Rationale: Prior research in mesial temporal lobe epilepsy (MTLE) has demonstrated that total bilateral hippocampal volume is inversely related to verbal memory function. However, most patients with MTLE have lateralized language function and sidedness of their seizure focus is often associated with ipsilateral structural changes (e.g., unilateral mesial temporal sclerosis). Verbal memory deficits are often prominent in MTLE and dominant hemisphere resection is more likely than nondominant resection to further perturb this function. The recent availability of an FDA-approved, automated quantitative volumetric measurement tool allows for comparison of unilateral structural changes associated with MTLE to baseline neurocognitive function. Methods: We studied preoperative high-resolution MR imaging and indices of verbal and spatial memory function on 17 patients with left hemisphere dominant language function (demonstrated by MEG, fMRI, or Wada) who subsequently underwent anterior temporal lobectomy (ATL). Hippocampal volume was calculated using the automated algorithms in Neuroreader. We used pearson correlations to compare memory indices to normalized hippocampal volume. Results: Left-hemisphere dominant patients undergoing ATL showed a significant positive correlation between left hippocampal volume z-scores and preoperative verbal memory encoding, r = 0.63, p = 0.009 and recall, r = 0.56, p = 0.02. This indicated that decreased left hippocampal volume was related to worse verbal memory performance. There was no relationship between right hippocampal volume and verbal memory encoding, p = 0.29, or recall, p = 0.17. Moreover, there was no relationship between left hippocampal volume z-scores and preoperative spatial memory encoding, p = 0.36, or recall, p = 0.54, nor was there relationship between right hippocampal volume z-scores and preoperative spatial memory encoding, p = 0.12, or recall, p = 0.50. Conclusions: In patients with left hemisphere dominance, left hippocampal volumetrics were positively correlated with verbal memory performance. The lack of a similar relationship between right hippocampal volume and verbal memory is consistent with the extant literature on the lateralization of language and related memory function. These findings suggest that automated quantitative volumetric measurement tools are sensitive to structural changes related to clinical symptomatology and can be a useful adjunct in the preoperative evaluation of patients with MTE. Funding: None