Evidence for Accelerated Hippocampal Volume Loss with Age in Patients with Left Hemisphere Focal Seizures
Abstract number :
2.178
Submission category :
5. Neuro Imaging / 5A. Structural Imaging
Year :
2022
Submission ID :
2205077
Source :
www.aesnet.org
Presentation date :
12/4/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:27 AM
Authors :
hong zheng, MD,MS – USC; Meredith Braskie, PhD – USC; Yaqiong Chai, PhD – USC; Elizabeth Haddad, PhD – USC; Neda Jahanshad, PhD – USC; Conor Owens-Walton, PhD – USC; Mohamad Shamas, PhD – Postdoc, Neurology, UCLA; Richard Staba, PhD – Professor in Neurology, Neurology, UCLA; Sophia Thomopoulos, Ms – USC; Paul Thompson, PhD – USC
Rationale: The hippocampus plays an important role in cognition, especially memory. Hippocampal volume also gradually declines with age in healthy controls. In addition to aging, studies show significant hippocampal alterations in neurological disorders such as epilepsy (Sutula, T.1989, Vrinda, M. 2019). Here we set out to assess the effects of aging and epilepsy on hippocampal volume, which could help determine the risk for hippocampal-dependent cognitive deficits in epilepsy.
Methods: We analyze brain MRI data from 109 controls and 97 patients with medication-resistant unilateral focal seizures (45 right- and 52 left-sided; 54 F / 43 M; age range: 20-72 years). Each subject’s 3T T1/w MRI was used to extract hippocampal volume using FreeSurfer v7.1 gross hippocampal segmentation (Fischl, B. 2002). Regression analysis was performed to evaluate the effects of age at time of MRI, condition (control vs. epilepsy), sex and ICV on hippocampal volume. Three strategies were used. First, separate models were generated for the hippocampus ipsilateral and contralateral to hemisphere of seizure onset, and then second, for each hippocampus with respect to right- and left-sided epilepsy. The third strategy created separate models for patients and controls while considering years since diagnosis as an additional variable in the patients’ model. A total of 1,000 permutations were run to randomly select a right or left hippocampus for each control while keeping equivalent right/left ratios between patients and controls.
Results: In the first analysis, 89% of the 1,000 iterations showed that older age and epilepsy significantly predicted reduced hippocampal volume ipsilateral, but not contralateral, to seizure onset. Similarly, the second analysis found older age and epilepsy significantly predicted lower hippocampal volume ipsilateral (p = .02), but not contralateral (p = .44), to seizure onset in left-sided epilepsy (Figure 1A). Age and/or epilepsy were not significant in right-sided epilepsy (p = .27 and .84, Figure 1B). Lastly, patients with left-sided, but not right-sided, epilepsy showed significant effect of age in both hemispheres (p = .03 and .01). There was no detectable effect of age on hippocampal volume in controls, perhaps due to limited power.
Conclusions: The current results are consistent with the hypothesis of accelerated hippocampal volume loss with advancing age in patients with poorly controlled seizures, especially in the ipsilateral and possibly contralateral hippocampus, in left-sided epilepsy (Figure 2). These results could indicate that some patients could have increased risk for hippocampal-dependent memory deficits. Other clinical factors, e.g., temporal or extratemporal lobe seizures, and comorbidities, likely modify aging effects in the epileptic hippocampus and will be the focus of future work.
Funding: NINDS R01NS106957
Neuro Imaging