Water Exchange across the Blood-Brain Barrier in Obstructive Sleep Apnea: An MRI Diffusion-Weighted Pseudo-Continuous Arterial Spin Labeling Study

BACKGROUND AND PURPOSEObstructive sleep apnea (OSA) subjects show brain injury in sites that control autonomic, cognitive, and mood functions that are deficient in the condition. The processes contributing to injury may include altered blood-brain barrier (BBB) actions. Our aim was to examine BBB function, based on diffusion-weighted pseudo-continuous arterial spin labeling (DW-pCASL) procedures, in OSA compared to controls. METHODSWe performed DW-pCASL imaging in nine OSA and nine controls on a 3.0-Tesla MRI scanner. Global mean gray and white matter arterial transient time (ATT, an index of large artery integrity), water exchange rate across the BBB (Kw, BBB function), DW-pCASL ratio, and cerebral blood flow (CBF) values were compared between OSA and control subjects. RESULTSGlobal mean gray and white matter ATT (OSA vs. controls; gray matter, 1.691 .120 vs. 1.658 +/- .109 second, P = .49; white matter, 1.700 +/- .115 vs. 1.650 +/- .114 second, P = .44), and CBF values (gray matter, 57.4 +/- 15.8 vs. 58.2 +/- 10.7 ml/100 g/min, P = .67; white matter, 24.2 +/- 7.0 vs. 24.6 +/- 6.7 ml/100 g/min, P = .91) did not differ significantly, but global gray and white matter Kw (gray matter, 158.0 +/- 28.9 vs. 220.8 +/- 40.6 min(-1), P = .002; white matter, 177.5 +/- 57.2 vs. 261.1 +/- 51.0 min(-1), P = .006), and DW-pCASL ratio (gray matter, .727 +/- .076 vs. .823 +/- .069, P = .011; white matter, .722 +/- .144 vs. .888 +/- .100, P = .004) values were significantly reduced in OSA over controls. CONCLUSIONSOSA subjects show compromised BBB function, but intact large artery integrity. The BBB alterations may introduce neural damage contributing to abnormal functions in OSA, and suggest a need to repair BBB function with strategies commonly used in other fields.