In epilepsy debilitating seizures often start within a single ‘focus’ of abnormal brain tissue but quickly spread to involve the entire brain. Historically most epilepsy research and treatments have been directed at the focus where seizures originate. However, there is increasing evidence that epilepsy should be thought of as a circuit level disorder whose impact extends to widely distributed brain networks.
One of the most common causes of epilepsy is mesial temporal sclerosis (MTS), a condition in which seizures start in the hippocampus, a region buried deep within the temporal lobe. In MTS the affected hippocampus often appears abnormal on structural MR images and surgically removing it can be curative. However, many MTS patients continue to experience cognitive and psychiatric symptoms even after their seizure focus is resected and their seizures cured, again suggesting that brain dysfunction in these patients extends beyond the hippocampus itself.
By measuring correlations in cortical thickness across the brain a technique called morphologic-covariance (mc) can reveal networks of spatially distinct cortical regions whose thickness is correlated suggesting that these regions may work together to perform certain functions and might be affected together by common pathologies. In this project we are applying mc to high-resolution structural MRI scans of patients with MTS to examine whether dysfunction in the brains of these patients extends beyond the affected hippocampus and adjacent temporal lobe to involve distant cortical regions in both the affected and unaffected hemisphere. Our ultimate goal is to use this and related techniques for mapping the brain’s functional connectivity to develop imaging biomarkers to improve diagnosis, surgical planning, and outcome prediction in individual epilepsy patients, and to provide a framework for understanding and potentially treating psychiatric comorbidity in this patient population.