"Atypical parkinsonism patients do tend to have more balance issues, and a complicated motor task requiring intact balance may provide a reasonable prognostic clue," said Dr. Mark Stacy of Duke University in an e-mail.
Dr. Paul Tuite of the University of Minnesota in Minneapolis echoed the comment. "The differences in the onset of postural impairment is already a key distinguishing feature between Parkinson's disease and atypical parkinsonism and this may be brought out by the bicycle question," he said in an e-mail.
But the fact that most U.S. adults haven't ridden bicycles in a very long time could stand in the way of broader application of what Bloem and colleagues called "the bicycle sign."
In fact, Tuite said he thought the sign would be "hard to utilize" because of the "rarity of cycling for people in their 40s, 50s and 60s."
Daniel Tarsy, MD, of Beth Israel Deaconess Medical Center in Boston, suggested that ability to perform other simple tasks requiring balance might work as well as the bike question.
"One example is whether a man finds it difficult to balance on one leg while putting on his trousers one leg at a time," he told MedPage Today and ABC News.