REM sleep behaviour disorder and Parkinson’s

Most people with REM sleep behaviour disorder (RBD), which makes them act out their dreams, later develop Parkinson’s disease or related conditions such as multiple systems atrophy or Lewy body dementia. At Western University, Dr. Penny MacDonald, a neurologist and Canada Research Chair, is using imaging technology to check for structural changes in the striatum region of the brains of people with this sleep disorder. If she finds these changes, they could be used to predict who will develop Parkinson’s and start treatment before motor symptoms emerge. 

REM sleep behaviour disorder is a relatively uncommon condition during which people act out their dreams while asleep, sometimes injuring their partners or themselves. Up to 80 percent of people with this disorder later develop Parkinson’s disease, multiple systems atrophy or Lewy body dementia.  

At Western University, Dr. Penny MacDonald, a neurologist, uses sophisticated Magnetic Resonance Imaging (MRI) technology to scan the brains of people with this sleep disorder. She’s checking for differences in the striatum region and sub-regions of the brain. Her research is made possible through a Parkinson Canada Pilot Project Grant funded by Pedaling for Parkinson’s in honour of Dr. Robert Lorne Alexander, in the amount of $32,984 over one year.

“One of the problems is that most therapies that we’ve tried to either slow, halt, or reverse Parkinson’s disease are not effective,” says MacDonald.

Part of the difficulty is that by the time people are diagnosed, researchers estimate they have already lost 60 to 80 percent of the dopamine-generating brain cells critical for motor control.

“If we could find a biomarker that predicts people who will develop Parkinson’s, that would allow us to start trying therapies at an earlier disease stage when they might be more effective,” says MacDonald.

MacDonald suspects that her imaging studies will show that the caudal motor portion of the striatum in people with this sleep disorder is smaller and has fewer nerve endings that connect to other regions of the brain. If she is correct, then this structural difference in the striatum could serve as a biomarker.  

By administering an MRI, doctors could then determine who is at risk for Parkinson’s and start treatment sooner.

“Maybe they (medications) would have greater efficacy before widespread loss of dopamine-producing cells occurs,” she says.

MacDonald earned a PhD in experimental psychology before she went to medical school to become a neurologist, because her first love was learning about the brain. But she thought research alone would not enable her to make a difference in this crucial field.

“I like to have the opportunity to apply the things that I know,” she says.

She now sees patients one day a week and spends the remainder of her time on research and teaching graduate and medical students. “It gives me more freedom to do whatever research I want, because I know that at least one day a week, I will be doing something very practical to help people, so I can be more adventurous in terms of the research that I pursue.”

Read about other researchers recently funded by the Parkinson Canada Research Program by visiting the research section of