Brain white matter changes in CPAP-treated obstructive sleep apnea patients with residual sleepiness.
To investigate white matter (WM) structural alterations using diffusion tensor imaging (DTI) in obstructive sleep apnea (OSA) patients, with or without residual sleepiness, following adherent continuous positive airway pressure (CPAP) treatment. Possible quantitative relationships were explored between the DTI metrics and two clinical assessments of somnolence.



Twenty-nine male patients (30-55 years old) with a confirmed diagnosis of OSA were recruited. The patients were treated with CPAP therapy only. The Psychomotor Vigilance Task (PVT) and Epworth Sleepiness Scale (ESS) were performed after CPAP treatment and additionally administered at the time of the magnetic resonance imaging (MRI) scan. Based on the PVT results, the patients were divided into a nonsleepy group (lapses ≤5) and a sleepy group (lapses >5). DTI was performed at 3T, followed by an analysis using tract-based spatial statistics (TBSS) to investigate the differences in fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (λ1), and radial diffusivity (λ23) between the two groups.



A higher MD (P < 0.05) was observed in the sleepy group than the nonsleepy group in the whole-brain TBSS analysis in the WM. The increased MD (17.8% of the fiber tracts; P < 0.05) was caused primarily by an elevated λ23. Axial diffusivity (λ1) exhibited no significant difference (P > 0.17). The alterations in FA or MD of individual fiber tracts occurred mainly in the internal/external capsule, corona radiata, corpus callosum, and sagittal stratum regions. The FA and MD values correlated with the PVT and ESS assessments from all patients (R ≥ 0.517, P < 0.05).



Global and regional WM alterations, as revealed by DTI, can be a possible mechanism to explain why OSA patients with high levels of CPAP use can have differing responses to treatment. Compromised myelin sheath, indicated by increased radial diffusivity, can be involved in the underlying WM changes. Evidence level: 1 J. MAGN. RESON. IMAGING 2017;45:1371-1378.
Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, Illinois, USA.|Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Ying
Y
Xiong
Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, Illinois, USA.|Department of Radiology, University of Illinois at Chicago, Chicago, Illinois, USA.|Department of Neurosurgery, University of Illinois at Chicago, Chicago, Illinois, USA.|Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, USA.
Xiaohong Joe
XJ
Zhou
College of Nursing, University of Illinois at Chicago, Chicago, Illinois, USA.
Robyn A
RA
Nisi
College of Nursing, University of Illinois at Chicago, Chicago, Illinois, USA.
Kelly R
KR
Martin
Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, Illinois, USA.
M Muge
MM
Karaman
Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, Illinois, USA.|Department of Radiology, University of Illinois at Chicago, Chicago, Illinois, USA.
Kejia
K
Cai
College of Nursing, University of Illinois at Chicago, Chicago, Illinois, USA.
Terri E
TE
Weaver
D000328:Adult; D016880:Anisotropy; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology*; D001931:Brain Mapping; D045422:Continuous Positive Airway Pressure; D003337:Corpus Callosum / Q000473:pathology; D003430:Cross-Sectional Studies; D004058:Diffusion; D056324:Diffusion Tensor Imaging / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009186:Myelin Sheath / Q000473:pathology; D012890:Sleep; D020181:Sleep Apnea, Obstructive / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D012894:Sleep Stages; D014851:Wakefulness; D066127:White Matter / Q000473:pathology*
CPAP; diffusion tensor imaging (DTI); obstructive sleep apnea (OSA); residual sleepiness; white matter