Structural and functional effects of circumscribed temporal lobe resections

• Applicant: Dr. Niels Alexander Foit
• Subject Area: Clinical Neurology; Neurosurgery and Neuroradiology
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 403231417

Temporal lobe epilepsy (TLE) is the most common drug-refractory focal epilepsy. While effective in seizure control, resection of the hippocampus (HC) of the dominant temporal lobe exposes patients to a risk of postoperative verbal memory decline. In TLE with extra-hippocampal seizure onset, “hippocampus-sparing” surgery aims at preserving the largest amount of functional tissue, reducing risks of neuropsychological deterioration. Nevertheless, we recently demonstrated VM decline in TLE patients after HC-sparing resections. Furthermore, significant postoperative ipsilateral hippocampal volume loss was observed, which correlated with reduced VM performance. Since the HC is part of a distributed memory network within the temporal lobe (TL), it is conceivable that even limited TL resection could disrupt this network, ultimately leading to HC atrophy through loss of input from afferent brain regions. To evaluate effects of TL lesionectomy on brain structure and function locally and at distance, the proposed project will target cohorts of patients with anterior TL resection (N=30), HC-s lesionectomy (N=20) and healthy controls (N=30).We will perform hippocampus subfield volumetry on pre- and post-operative MRI to evaluate subfield-specific postoperative alterations. Results will be correlated with neuropsychological data (confrontation naming, verbal fluency, verbal free recall, short-term memory). Additionally, linear models will be used to relate the impact of HC-s surgery on cortical connectivity appreciated through diffusion-tensor imaging locally within the TL and at large-scale. Moreover, we will build predictive models of post-operative cognitive outcome based on structural and functional connectivity metrics.Postoperative memory decline is a serious complication in TLE surgery, with strong impact on postoperative quality of life. Better understanding of the effects of surgery on TL structural and functional networks will allow for the prediction of postoperative neuropsychological performance. In patients at high-risk for VM loss, this will ultimately aid in preoperative counseling and clinical decision making

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professor Andrea Bernasconi, Ph.D.