title: Electrical conductivities of the freshly excised cerebral cortex in epilepsy surgery patients; correlation with pathology, seizure duration, and diffusion tensor imaging.
abstract: The electrical conductivities (sigma) of freshly excised neocortex and subcortical white matter were studied in the frequency range of physiological relevance for EEG (5-1005 Hz) in 21 patients (ages 0.67 to 55 years) undergoing epilepsy neurosurgery. Surgical patients were classified as having cortical dysplasia (CD) or non-CD pathologies. Diffusion tensor imaging (DTI) for apparent diffusion coefficient (ADC) and fractional anisotropy (FA) was obtained in 9 patients. Results found that electrical conductivities in freshly excised neocortex vary significantly from patient to patient (sigma = 0.0660-0.156 S/m). Cerebral cortex from CD patients had increased conductivities compared with non-CD cases. In addition, longer seizure durations positively correlated with conductivities for CD tissue, while they negatively correlated for non-CD tissue. DTI ADC eigenvalues inversely correlated with electrical conductivity in CD and non-CD tissue. These results in a small initial cohort indicate that electrical conductivity of freshly excised neocortex from epilepsy surgery patients varies as a consequence of clinical variables, such as underlying pathology and seizure duration, and inversely correlates with DTI ADC values. Understanding how disease affects cortical electrical conductivity and ways to non-invasively measure it, perhaps through DTI, could enhance the ability to localize EEG dipoles and other relevant information in the treatment of epilepsy surgery patients.
authors.affiliation: Brain Mapping Division, Neuropsychiatric Institutes, David Geffen School of Medicine, University of California-Los Angeles, Room 215-A, 660 Charles Young Drive South, Los Angeles, CA, USA. Akhtarim@ucla.edu
authors.forename: M
authors.initials: M
authors.lastname: Akhtari
authors.forename: N
authors.initials: N
authors.lastname: Salamon
authors.forename: R
authors.initials: R
authors.lastname: Duncan
authors.forename: I
authors.initials: I
authors.lastname: Fried
authors.forename: G W
authors.initials: GW
authors.lastname: Mathern
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000465:Algorithms; D016880:Anisotropy; D001706:Biopsy; D002540:Cerebral Cortex / Q000002:abnormalities / Q000473:pathology / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging; D004569:Electroencephalography; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015225:Magnetoencephalography; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology*; D009434:Neural Pathways / Q000473:pathology / Q000503:physiopathology*; D013223:Statistics as Topic / Q000379:methods; D013997:Time Factors