title: Impaired cerebrovascular reactivity in multiple sclerosis.
abstract: OBJECTIVE
  Cerebrovascular reactivity (CVR) is an inherent indicator of the dilatory capacity of cerebral arterioles for a vasomotor stimulus for maintaining a spontaneous and instant increase of cerebral blood flow (CBF) in response to neural activation. The integrity of this mechanism is essential to preserving healthy neurovascular coupling; however, to our knowledge, no studies have investigated whether there are CVR abnormalities in multiple sclerosis (MS).
  
  
  OBJECTIVE
  To use hypercapnic perfusion magnetic resonance imaging to assess CVR impairment in patients with MS.
  
  
  METHODS
  A total of 19 healthy volunteers and 19 patients with MS underwent perfusion magnetic resonance imaging based on pseudocontinuous arterial spin labeling to measure CBF at normocapnia (ie, breathing room air) and hypercapnia. The hypercapnia condition is achieved by breathing 5% carbon dioxide gas mixture, which is a potent vasodilator causing an increase of CBF.
  
  
  METHODS
  Cerebrovascular reactivity was calculated as the percent increase of normocapnic to hypercapnic CBF normalized by the change in end-tidal carbon dioxide, which was recorded during both conditions. Group analysis was performed for regional and global CVR comparison between patients and controls. Regression analysis was also performed between CVR values, lesion load, and brain atrophy measures in patients with MS.
  
  
  RESULTS
  A significant decrease of mean (SD) global gray matter CVR was found in patients with MS (3.56 [0.81]) compared with healthy controls (5.08 [1.56]; P = .001). Voxel-by-voxel analysis showed diffuse reduction of CVR in multiple regions of patients with MS. There was a significant negative correlation between gray matter CVR and lesion volume (R = 0.6, P = .004) and a significant positive correlation between global gray matter CVR and gray matter atrophy index (R = 0.5, P = .03).
  
  
  CONCLUSIONS
  Our quantitative imaging findings suggest impairment in functional cerebrovascular pathophysiology, by measuring a diffuse decrease in CVR, which may be the underlying cause of neurodegeneration in MS.
authors.affiliation: Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York.
authors.forename: Olga
authors.initials: O
authors.lastname: Marshall
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas.
authors.forename: Hanzhang
authors.initials: H
authors.lastname: Lu
authors.affiliation: Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Brisset
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas.
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas.
authors.forename: Peiying
authors.initials: P
authors.lastname: Liu
authors.affiliation: Department of Neurology, Multiple Sclerosis Comprehensive Care Center, New York University School of Medicine, New York.
authors.forename: Joseph
authors.initials: J
authors.lastname: Herbert
authors.affiliation: Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Grossman
authors.affiliation: Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Ge
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D002245:Carbon Dioxide; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D066128:Gray Matter / Q000098:blood supply / Q000473:pathology; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D020528:Multiple Sclerosis, Chronic Progressive / Q000473:pathology / Q000503:physiopathology*; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000473:pathology / Q000503:physiopathology*; D012044:Regression Analysis; D014664:Vasodilation / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide