Emory University researchers find that functional imaging of the brain could shed light on the underlying disease in hypersomnolence disorders.

By Lisa Spear

Emerging research is exploring how functional imaging can reveal insights about brain metabolism in people with hypersomnia disorders.

An abstract published in a recent edition of SLEEP, FDG-PET Imaging In Narcolepsy Type 1, Idiopathic Hypersomnia, And Non-Sleepy Controls, finds different patterns of metabolic activity in narcolepsy and in idiopathic hypersomnia. According to the authors, these results imply disease-specific activity rather than non-specific sleepiness.

“PET [positron emission tomography] imaging doesn’t have a role in the clinical evaluation of narcolepsy type 1 (or idiopathic hypersomnia) right now. But these types of studies may help advance our scientific understanding of these disorders in ways that ultimately advance clinical care,” says coauthor Emory University neurologist Lynn Marie Trotti, MD, MSc.

“We’re not to the point of applying this clinically, but there is so little that is known about the biology of idiopathic hypersomnia that I hope this will be one piece of a much larger puzzle that leads to better treatment options.”

The researchers compared narcolepsy type 1 and hypersomnia patients against a control group of non-sleepy subjects. The fluorodeoxyglucose (FDG)-PET imagining showed differences in brain activation in all of the groups, suggesting that each hypersomnolence disorder has a different pattern of brain activation.

Trotti explains that future research is needed to better understand how this information can be used in clinical settings.

“We definitely need to know more about neurologic function in both of these disorders.  My hope was that by comparing and contrasting these two groups of sleepy participants—and a group of non-sleepy control participants—we could identify areas of regional hyper- or hypo-metabolism that are shared across both disorders and those that might be a more unique signature of one or the other,” says Trotti.

“The main point is that we don’t see identical patterns in the two hypersomnolence disorders.  Some of the differences between sleepy patients and controls that we see on PET are likely non-specific manifestations of sleepiness (or of trying to stay awake). But, because the two sleepy groups don’t have identical patterns, PET is still potentially telling us something about the underlying disease states—not just sleepiness itself—and larger studies are worth pursuing.”

Lisa Spear is associate editor of Sleep Review.