Perfusion MRI shows CPAP healing the brains of apnea patients

It’s well established that widely used CPAP devices help give a good night’s rest to people with obstructive sleep apnea. Now an MRI-based study has shown the breathing assistance provided by continuous positive airway pressure also increases blood flow to, and blood volume in, the brain.

The result may be the restoration of brain tissue damaged by hypoxemia.

That’s according to researchers at the University of Toronto and Tel Aviv University whose pilot study is set to run in the May edition of Sleep Medicine.

Hillel Maresky, MD, Sigal Tal, MD, and colleagues recruited seven patients with obstructive sleep apnea from a sleep center, treating them with six weeks of CPAP.  

The researchers scanned the participants (six men, one woman, mean age 51) with perfusion MRI of the brain before and after the treatment. They quantified microstructural changes using fractional anisotropy and mean diffusivity while quantifying brain perfusion using cerebral blood flow as well as volume.

Post-treatment, the team found several brain changes. Among these were increases in both cerebral blood flow and cerebral blood volume, indicating increases in brain perfusion capability.

Additionally, they observed that increases in fractional anisotropy corresponded with decreases in mean diffusivity in regions of the brain relating to cognition, memory, vision and language.

Also, decreases in fractional anisotropy showed up with corresponding increases in mean diffusivity, which the researchers observed in regions of the brain relating to sensory and motor functions.

In their discussion, the authors noted that the brain consumes more oxygen than any other organ, underscoring that decreased oxygenation associated with obstructive sleep apnea creates a state of persistent oxygen deprivation. This may lead to damage of the cerebral vasculature and loss of autoregulatory mechanisms.

“Continued hypoxia results in reactive oxygen species production, which may further limit brain repair mechanisms,” they added. “CPAP treatment … addresses the source of the problem by reversing the mechanism underlying hypoxia, thus increasing oxygenation. This likely limits reactive oxygen species production, a factor contributing to hypoxia-induced cellular damage, which can then allow for the activation of the brain’s repair mechanisms.”