title: Brain MRI CO2 stress testing: a pilot study in patients with concussion.
abstract: BACKGROUND
  There is a real need for quantifiable neuro-imaging biomarkers in concussion. Here we outline a brain BOLD-MRI CO2 stress test to assess the condition.
  
  
  METHODS
  This study was approved by the REB at the University of Manitoba. A group of volunteers without prior concussion were compared to post-concussion syndrome (PCS) patients--both symptomatic and recovered asymptomatic. Five 3-minute periods of BOLD imaging at 3.0 T were studied--baseline 1 (BL1--at basal CO2 tension), hypocapnia (CO2 decreased ∼5 mmHg), BL2, hypercapnia (CO2 increased ∼10 mmHg) and BL3. Data were processed using statistical parametric mapping (SPM) for 1st level analysis to compare each subject's response to the CO2 stress at the p = 0.001 level. A 2nd level analysis compared each PCS patient's response to the mean response of the control subjects at the p = 0.05 level.
  
  
  RESULTS
  We report on 5 control subjects, 8 symptomatic and 4 asymptomatic PCS patients. Both increased and decreased response to CO2 was seen in all PCS patients in the 2nd level analysis. The responses were quantified as reactive voxel counts: whole brain voxel counts (2.0±1.6%, p = 0.012 for symptomatic patients for CO2 response < controls and 3.0±5.1%, p = 0.139 for CO2 response > controls: 0.49±0.31%, p = 0.053 for asymptomatic patients for CO2 response < controls and 4.4±6.8%, p = 0.281 for CO2 response > controls).
  
  
  CONCLUSIONS
  Quantifiable alterations in regional cerebrovascular responsiveness are present in concussion patients during provocative CO2 challenge and BOLD MRI and not in healthy controls. Future longitudinal studies must aim to clarify the relationship between CO2 responsiveness and individual patient symptoms and outcomes.
authors.affiliation: Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: W Alan C
authors.initials: WA
authors.lastname: Mutch
authors.affiliation: Department of Surgery, Section of Neurosurgery, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ellis
authors.affiliation: Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: M Ruth
authors.initials: MR
authors.lastname: Graham
authors.affiliation: Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Wourms
authors.affiliation: Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Roshan
authors.initials: R
authors.lastname: Raban
authors.affiliation: Department of Anesthesia and Pain Management, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
authors.affiliation: Department of Radiology, Section of Neuroimaging, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Mikulis
authors.affiliation: Department of Surgery, Pan Am Clinic, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Leiter
authors.affiliation: Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Ryner
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001924:Brain Concussion / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000097:blood* / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000097:blood*; D016857:Hypocapnia / Q000097:blood*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging; D010865:Pilot Projects; D038223:Post-Concussion Syndrome; D011859:Radiography; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002245:Carbon Dioxide