Functional central nervous system imaging in the investigation of obstructive sleep apnea

Purpose of review This review summarizes recent neuroimaging research into cerebral alterations observed in obstructive sleep apnea. Studies applying neuroimaging techniques over the past 10 years have made important contributions to our understanding of the neurocognitive changes associated with this disorder. Recent findings Converging experiments using different methods (transcranial Doppler, event-related potentials, magnetic resonance spectroscopy, and structural and functional magnetic resonance imaging) demonstrated changes in cerebral blood flow, metabolism, morphology, and brain activation in response to cognitive challenges in patients with obstructive sleep apnea. Summary Obstructive sleep apnea is associated with unique cerebral alterations that may explain the changes in behavior and cognition observed. Their high temporal and spatial resolution mean that functional magnetic resonance imaging techniques may provide important information regarding the cerebral changes associated with cognitive performance in obstructive sleep apnea. Studies should control for obstructive sleep apnea-associated changes in basal cerebral blood flow, however. In addition, further research using standardized morphologic techniques is needed to better localize and characterize the pattern of neuronal loss in obstructive sleep apnea. Likewise, techniques to examine cerebral white matter integrity will be important in fully elucidating the impact of obstructive sleep apnea on the brain, as well as any recovery in brain function and cognitive performance following treatment.