Narcolepsy alters the pulsations that maintain the brain’s waste clearance system, shows a new study from the University of Oulu.

Researchers at the University of Oulu in Finland imaged the brains of narcolepsy patients using fast functional magnetic resonance imaging (fMRI). The method has previously been used to study Alzheimer’s disease as well as epilepsy and normal sleep.

Three types of pulsations are associated with brain clearance: cardiovascular pulsations of the brain arteries produced by the heartbeat, respiratory pulsations of the veins and cerebrospinal fluid, and slow vasomotor fluctuation of the vessel walls. The study showed that people with narcolepsy experience changes in all three types of brain pulsation.

Changes in pulsations were associated with the severity of the disease. Abnormalities in cardiac pulsation in brain regions relevant to narcolepsy were associated with the severity of symptoms experienced by the patient, with lower variability in cardiac pulsation predicting more severe symptoms. According to the researchers, this finding could be useful in optimizing the treatment response to narcolepsy.

The study included 22 people with narcolepsy and an equal number of healthy sex- and age-matched controls.

The brain’s waste clearance or glymphatic system is a relatively new discovery and currently the subject of intense research. The University of Oulu’s Oulu Functional Neuroimaging (OFNI) research group has previously shown that brain pulsations are linked to the brain’s clearance system. They have also described pulsation abnormalities in people with Alzheimer’s disease. In the future, it is possible that brain pulsation optimization might lead to new treatments for different diseases.

Narcolepsy is a neurological disease that impairs a patient’s quality of life and causes chronic daytime sleepiness. It affects the state of alertness, the functioning of the involuntary nervous system, and the production of certain neurotransmitters in the brain. 

“What’s interesting is that the regulation of the brain’s clearance system is linked to these very same functions. This finding links narcolepsy to the brain’s clearance system, and this is also the main finding of our study: the pulsations that maintain the brain’s clearance system are altered in people with narcolepsy compared to healthy controls,” says Matti Järvelä, MD, PhD student from the Functional Neuroimaging research group, in a release.

Narcolepsy onset occurs at a young age. There is no cure for it, and it may take years to diagnose. Usually, a diagnosis of narcolepsy is based on clinical symptoms, tests measuring sleep, and the rate of falling asleep, and sometimes includes analysis of a spinal fluid sampling and determination of genetic susceptibility.

The brain imaging method used in the study was able to distinguish between patients with narcolepsy and healthy patients. It could therefore have potential in the future as a diagnostic tool. 

“In an ideal situation, the actual examination takes only ten minutes, which is a significant improvement in terms of time. The method is also noninvasive, so there is no need for sampling. However, the accuracy of the study is probably best when combined with other diagnostics, and the results are still preliminary at this stage,” Järvelä says.

Faster diagnosis of the disease would allow treatments to start earlier and reduce the burden of disease experienced by patients. Since problems with the waste clearance system are also linked to the brain’s ability to maintain homeostasis, narcolepsy patients are likely to benefit from early treatment in the long term.

The study was published in Communications Medicine, a part of Nature Publishing Group. The research was funded by the Academy of Finland, the Jane and Aatos Erkko Foundation and the Emil Aaltonen Foundation.

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