title: Neuroimaging Assessment of Cerebrovascular Reactivity in Concussion: Current Concepts, Methodological Considerations, and Review of the Literature.
abstract: Concussion is a form of traumatic brain injury (TBI) that presents with a wide spectrum of subjective symptoms and few objective clinical findings. Emerging research suggests that one of the processes that may contribute to concussion pathophysiology is dysregulation of cerebral blood flow (CBF) leading to a mismatch between CBF delivery and the metabolic needs of the injured brain. Cerebrovascular reactivity (CVR) is defined as the change in CBF in response to a measured vasoactive stimulus. Several magnetic resonance imaging (MRI) techniques can be used as a surrogate measure of CBF in clinical and laboratory studies. In order to provide an accurate assessment of CVR, these sequences must be combined with a reliable, reproducible vasoactive stimulus that can manipulate CBF. Although CVR imaging currently plays a crucial role in the diagnosis and management of many cerebrovascular diseases, only recently have studies begun to apply this assessment tool in patients with concussion. In order to evaluate the quality, reliability, and relevance of CVR studies in concussion, it is important that clinicians and researchers have a strong foundational understanding of the role of CBF regulation in health, concussion, and more severe forms of TBI, and an awareness of the advantages and limitations of currently available CVR measurement techniques. Accordingly, in this review, we (1) discuss the role of CVR in TBI and concussion, (2) examine methodological considerations for MRI-based measurement of CVR, and (3) provide an overview of published CVR studies in concussion patients.
authors.affiliation: Department of Surgery, University of Manitoba, Winnipeg, MB, Canada; Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, MB, Canada; Section of Neurosurgery, University of Manitoba, Winnipeg, MB, Canada; Pan Am Concussion Program, University of Manitoba, Winnipeg, MB, Canada; Childrens Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, MB, Canada; Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ellis
authors.affiliation: Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; Department of Radiology, University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Lawrence N
authors.initials: LN
authors.lastname: Ryner
authors.affiliation: Institute of Medical Sciences, University of Toronto , Toronto, ON , Canada.
authors.forename: Olivia
authors.initials: O
authors.lastname: Sobczyk
authors.affiliation: Department of Neurosurgery, University Hospital Zurich , Zurich , Switzerland.
authors.forename: Jorn
authors.initials: J
authors.lastname: Fierstra
authors.affiliation: Department of Medical Imaging, University of Toronto, Toronto, ON, Canada; University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada.
authors.forename: David J
authors.initials: DJ
authors.lastname: Mikulis
authors.affiliation: University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Anesthesia, University of Toronto, Toronto, ON, Canada.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
authors.affiliation: University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada.
authors.forename: James
authors.initials: J
authors.lastname: Duffin
authors.affiliation: Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada; Department of Anesthesia and Perioperative Medicine, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: W Alan C
authors.initials: WA
authors.lastname: Mutch
keywords: blood oxygen level-dependent imaging; carbon dioxide; cerebrovascular reactivity; concussion; magnetic resonance imaging