title: Delayed and disorganised brain activation detected with magnetoencephalography after mild traumatic brain injury.
abstract: BACKGROUND
  Awareness to neurocognitive issues after mild traumatic brain injury (mTBI) is increasing, but currently no imaging markers are available for mTBI. Advanced structural imaging recently showed microstructural tissue changes and axonal injury, mild but likely sufficient to lead to functional deficits. Magnetoencephalography (MEG) has high temporal and spatial resolution, combining structural and electrophysiological information, and can be used to examine brain activation patterns of regions involved with specific tasks.
  
  
  METHODS
  16 adults with mTBI and 16 matched controls were submitted to neuropsychological testing (Wechsler Abbreviated Scale of Intelligence (WASI); Conners; Alcohol Use Disorders Identification Test (AUDIT); Generalised Anxiety Disorder Seven-item Scale (GAD-7); Patient Health Questionnaire (PHQ-9); Symptom Checklist and Symptom Severity Score (SCAT2)) and MEG while tested for mental flexibility (Intra-Extra Dimensional set-shifting tasks). Three-dimensional maps were generated using synthetic aperture magnetometry beamforming analyses to identify differences in regional activation and activation times. Reaction times and accuracy between groups were compared using 2×2 mixed analysis of variance.
  
  
  RESULTS
  While accuracy was similar, patients with mTBI reaction time was delayed and sequence of activation of brain regions disorganised, with involvement of extra regions such as the occipital lobes, not used by controls. Examination of activation time showed significant delays in the right insula and left posterior parietal cortex in patients with mTBI.
  
  
  CONCLUSIONS
  Patients with mTBI showed significant delays in the activation of important areas involved in executive function. Also, more regions of the brain are involved in an apparent compensatory effort. Our study suggests that MEG can detect subtle neural changes associated with cognitive dysfunction and thus, may eventually be useful for capturing and tracking the onset and course of cognitive symptoms associated with mTBI.
authors.affiliation: Division of Neurosurgery, Sunnybrook Hospital, University of Toronto, Toronto, Ontario, Canada Department of Medical Imaging, Sunnybrook Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Leodante
authors.initials: L
authors.lastname: da Costa
authors.affiliation: Neurosciences and Mental Health, SickKids Research Institute, Toronto, Ontario, Canada.
authors.forename: Amanda
authors.initials: A
authors.lastname: Robertson
authors.affiliation: Division of Neurosurgery, Sunnybrook Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Allison
authors.initials: A
authors.lastname: Bethune
authors.affiliation: Neurosciences and Mental Health, SickKids Research Institute, Toronto, Ontario, Canada.
authors.forename: Matt J
authors.initials: MJ
authors.lastname: MacDonald
authors.affiliation: Military Medicine Section, Defence Research and Development Canada, Toronto, Ontario, Canada.
authors.forename: Pang N
authors.initials: PN
authors.lastname: Shek
authors.affiliation: Neurosciences and Mental Health, SickKids Research Institute, Toronto, Ontario, Canada Department of Diagnostic Imaging, Hospital for Sick Children, Toronto, Ontario, Canada Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Margot J
authors.initials: MJ
authors.lastname: Taylor
authors.affiliation: Neurosciences and Mental Health, SickKids Research Institute, Toronto, Ontario, Canada Division of Neurology, Hospital for Sick Children, Toronto, Ontario, Canada Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Elizabeth W
authors.initials: EW
authors.lastname: Pang
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001930:Brain Injuries / Q000150:complications / Q000503:physiopathology* / Q000523:psychology; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D056344:Executive Function / Q000502:physiology*; D006801:Humans; D015601:Injury Severity Score; D015225:Magnetoencephalography; D008297:Male; D009483:Neuropsychological Tests; D055815:Young Adult
keywords: BRAIN MAPPING; COGNITIVE ELECTROPHYSIOLOGY; HEAD INJURY