title: Polymicrogyric Cortex may Predispose to Seizures via Abnormal Network Topology: An fMRI Connectomics Study.
abstract: Polymicrogyria is a significant malformation of cortical development with a high incidence of epilepsy and cognitive deficits. Graph theoretic analysis is a useful approach to studying network organization in brain disorders. In this study, we used task-free functional magnetic resonance imaging (fMRI) data from four patients with polymicrogyria and refractory epilepsy. Gray matter masks from structural MRI data were parcellated into 1,024 network nodes. Functional "connectomes" were obtained based on fMRI time series between the parcellated network nodes; network analysis was conducted using clustering coefficient, path length, node degree, and participation coefficient. These graph metrics were compared between nodes within polymicrogyric cortex and normal brain tissue in contralateral homologous cortical regions. Polymicrogyric nodes showed significantly increased clustering coefficient and characteristic path length. This is the first study using functional connectivity analysis in polymicrogyria--our results indicate a shift toward a regular network topology in polymicrogyric nodes. Regularized network topology has been demonstrated previously in patients with focal epilepsy and during focal seizures. Thus, we postulate that these network alterations predispose to seizures and may be relevant to cognitive deficits in patients with polymicrogyria.
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Austin Campus, Heidelberg, Victoria, Australia.|Florey Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia.|Department of Neurology, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Moksh
authors.initials: M
authors.lastname: Sethi
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Austin Campus, Heidelberg, Victoria, Australia.|Florey Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Mangor
authors.initials: M
authors.lastname: Pedersen
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Austin Campus, Heidelberg, Victoria, Australia.|Florey Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia.|Department of Neurology, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Graeme D
authors.initials: GD
authors.lastname: Jackson
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D063132:Connectome / Q000379:methods; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009415:Nerve Net / Q000503:physiopathology*; D065706:Polymicrogyria / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D012640:Seizures / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D055815:Young Adult
keywords: Cortical malformations; Focal epilepsy; Graph theory; Polymicrogyria; Resting state functional connectivity