Sniffing out Parkinson’s disease
Chemosensory impairment in Parkinson's disease
Losing their sense of smell is an early symptom that most people with Parkinson’s disease experience. That’s why some researchers are targeting the olfactory system, to use it to predict who will develop the disease.
Because there are many other reasons besides Parkinson’s that people lose their sense of smell, however, Dr. Johannes Frasnelli is hoping another sensory system will provide better diagnostic clues. Frasnelli, a neuroscientist and professor at the Université de Montréal at Trois-Rivières, is focused on the trigeminal chemosensory system. The trigeminal system—which most people aren’t even aware they use—is a part of the nervous system that helps us perceive the spiciness of hot peppers or the freshness of peppermint.
Frasnelli is trying to pinpoint patterns of impairment affecting the trigeminal system that are specific to Parkinson’s disease. Recognizing that pattern could form the basis of a diagnostic test or marker.
“The benefit of early detection would be to develop tools so we could at least stop the progress of this disease,” Frasnelli says.
The trigeminal system consists of receptors in the nose and mouth that are independent of our sense of smell and taste. Typically, though, someone who has lost their sense of smell would also become less sensitive to spiciness, burning and cooling sensations.
But Frasnelli suspects that people with Parkinson’s disease do not have a reduction in the trigeminal system, meaning they can still perceive those sharp and spicy sensations. He’s comparing groups of people who have lost their sense of smell for another reason to those with Parkinson’s disease, and to healthy people, to try to isolate a unique pattern or profile of those who are at risk of developing Parkinson’s.
If he discovers that people with Parkinson’s can’t smell most odours but can still perceive the fresh, burning or spicy sensation, testing that might provide a good diagnostic marker.
“We will then have a better way of evaluating who are most at risk and those who are less at risk,” Frasnelli says.
That evaluation is critical because by the time Parkinson’s is diagnosed, most people have already lost 60 percent of their dopamine-producing brain cells.
Frasnelli, who trained as a doctor in Germany, prefers research to clinical work with patients because he can satisfy his curiosity about problems that affect people, including those with Parkinson’s he says.
“With research, you can ask questions where there is no answer, and you have to find the answer yourself,” he says. “That’s extremely interesting.”