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Brain oxygenation responses to autonomic challenge: a quantitative fMRI investigation of the Valsalva manoeuvre

Lookup NU author(s): Dr Iwo Bohr, Dr Claire McDonald, Dr Jiabao He, Dr Simon Kerr, Professor Julia Newton, Professor Andrew Blamire

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Abstract

In late age the autonomic nervous system (ANS) has diminished ability to maintain physiological homeostasis in the brain in response to challenges such as to systemic blood pressure changes caused by standing. We devised an fMRI experiment aiming to map the cerebral effects of an ANS challenge (Valsalva manoeuvre; VM). We used dual-echo fMRI to measure the effective transverse relaxation rate (R2*, which is inversely proportional to brain tissue oxygenation levels) in 45 elderly subjects (median age: 80 years old, total range: 75-89) during performance of the VM. In addition we collected Fluid Attenuation Inversion Recovery (FLAIR) data from which we quantified white matter hyperintensity (WMH) volumes. We conducted voxelwise analysis of the dynamic changes in R2* during the VM to determine the distribution of oxygenation changes due to the autonomic stressor. In white matter we observed significant decreases in oxygenation levels. These effects were predominantly located in posterior white matter and to a lesser degree in the right anterior brain, both concentrated around the border zones (watersheds) between cerebral perfusion territories. These areas are known to be particularly vulnerable to hypoxia and are prone to formation of white matter hyperintensities. Although we observed overlap between localization of WMH and triggered deoxygenation on the group level we did not find significant association between these independent variables using subject-wise statistics. This could suggest other than recurrent transient hypoxia mechanisms causing/contributing to the formation of WMH.


Publication metadata

Author(s): Bohr I, McDonald C, He J, Kerr S, Newton J, Blamire AM

Publication type: Article

Publication status: Published

Journal: AGE

Year: 2015

Volume: 37

Print publication date: 01/10/2015

Online publication date: 29/08/2015

Acceptance date: 20/08/2015

ISSN (print): 0161-9152

ISSN (electronic): 1574-4647

Publisher: Springer

URL: http://dx.doi.org/10.1007/s11357-015-9833-6

DOI: 10.1007/s11357-015-9833-6


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