Abstracts

Rationale: Converging evidence from imaging and EEG studies suggest that focal epilepsy is a network disorder, with abnormal brain function extending beyond primary epileptogenic brain regions. It remains unclear if abnormal brain networks in focal epilepsy precede epilepsy onset or are a consequence of ongoing seizures. We investigated network abnormalities in newly diagnosed focal epilepsy patients using baseline resting state fMRI imaging obtained as part of the Human Epilepsy Project (HEP). Previous independent work has demonstrated changes in graph theoretical metrics, including clustering coefficient, local efficiency and modularity, that are associated with extratemporal epilepsy [1]. We applied a similar analytic framework to HEP participants in order to determine if network abnormalities exist close to epilepsy onset, and determine if these network measures may be potential markers for health outcomes in focal epilepsy. Methods: Baseline resting state functional MRI has been acquired in 62 HEP participants and 38 healthy controls, imaged on a single Siemens Allegra 3T MRI scanner. Subjects were scanned at rest using an EPI BOLD acquisition for 6 min 40 s with a TR= 2s, yielding 200 volumes, and a whole brain T1w MRI scan was acquired. Images were processed using SPM8 and the DPARSF matlab toolbox for resting state fMRI analysis. Network metrics were assessed using the Brain Connectivity Toolbox. Results: Analysis of local efficiency in newly diagnosed HEP participants revealed a bimodal distribution of values, with a subset of HEP patients displaying increased local efficiency relative to healthy controls (Figure 1). Conclusions: The observation of increased local efficiency in newly diagnosed focal epilepsy patients suggests that network abnormalities may exist close to epilepsy onset. The observation of increased local efficiency is similar to that observed in a prior cohort of extratemporal cases [1]. These findings provide compelling evidence that a subset of HEP participants have functional network properties that resemble intractable focal epilepsy. Assessment of seizure outcomes will allow us to determine if the local efficiency metric, assessed at treatment onset, is a marker of future intractability in focal epilepsy.[1] Pedersen et al Neuroimage: Clinical (2015) Vol 8 536-542 Funding: The HEP study is supported by the Epilepsy Study Consortium (ESCI), a non-profit organization dedicated to accelerating the development of new therapies in epilepsy to improve patient care. The funding provided to ESCI to support HEP comes from industry, philanthropy and foundations (UCB Pharma, Eisai, Pfizer, Lundbeck, Sunovion, The Andrews Foundation, The Vogelstein Foundation, Finding A Cure for Epilepsy and Seizures (FACES), Friends of Faces and others).