Reduction in regional cerebral blood flow in obstructive sleep apnea during wakefulness: A high-resolution SPECT study

Abstract

Introduction Obstructive sleep apnea (OSA) is characterized by recurrent respiratory pauses that cause hypoxemia and sleep fragmentation. OSA is known to be associated with daytime sleepiness, cognitive deficits, and altered brain functioning. The objective of this study is to investigate changes in regional cerebral blood flow (rCBF) at rest using a high- resolution single photon emission computed tomography (SPECT) system in patients with OSA, compared to healthy subjects. Materials and methods rCBF of 9 OSA patients (apnea- hypopnea index (AHI): 39.7 ± 16.9; age: 66.1 ± 7.8 years) and 9 control subjects (AHI 2.5 ± 1.8; age: 67.9 ± 9.0 years) matched for body mass index were evaluated with 99Tc-HMPAO SPECT. Hypoperfusions in OSA subjects were compared to control subjects using statistical parametric mapping with independent t-tests with a significance threshold of 0.05 corrected for multiple comparisons for clusters and 0.001 uncorrected for peaks. Results OSA subjects showed significant reductions of rCBF in bilateral inferior parietal lobules (Brodmann area (BA): 40), left superior temporal gyrus (BA: 39) and left medial frontal gyrus (BA: 6) compared to control subjects. Conclusion These preliminary results show that OSA is associated with reduction of rCBF in several cortical regions that are known to be part of the default mode network. This network is a set of associative structures involved in internal cognition (e.g. planning and episodic memory). Altered rCBF in this network could be associated with cognitive deficits generally observed in OSA or with early signs of neurodegenerative disorders, but further studies with larger samples will be needed to investigate this relationship. Acknowledgements Supported by the Canadian Institutes of Health Research and the COPSE of the Faculty of Medicine of Universite de Montreal.