A Bicyclist with Advanced PD Takes Off
What the Unique Case Means
ARTICLE IN BRIEF
tinvestigators describe a case report of a patient with advanced Parkinson disease who has freezing gait but who can bicycle fluidly. Experts speculate why the patient can still ride a bicycle
What does one Parkinson disease (PD) patient with a bicycle have to teach movement disorders experts? Quite a lot, possibly. The patient, a 58-year-old man from the Netherlands, is incapacitated on foot, but rides a bicycle with confidence and ease. His case is featured in an April 1 online report in the New England Journal of Medicine, accompanied by a video available on the journal's Web site.
The video begins with the patient standing in a hospital hallway, frozen in place and unable to move. After 20 seconds, and only with assistance and repeated visual cuing, he succeeds in taking several small steps, but he quickly loses his balance, and is only rescued from falling by the intervention of an attendant. We next see him in the hospital parking lot, seated on a bicycle. With a push from two attendants, he is off pedaling down the pavement, as smooth and steady as can be.
After perhaps 100 meters, he coasts while executing a flawless 180 degree turn, then pedals back toward the camera, even elevating himself off the saddle at one point to gain extra power on the pedals. He glides to a stop, makes an agile hop off the saddle to dismount, and steps again onto the pavement. And he is once more frozen in place.
According to senior author Bastiaan Bloem, MD, professor of neurology at Radboud University Nijmegen Medical Center, in Nijmegen, the Netherlands, the patient is, like many in the Netherlands, an avid cyclist. He came to Dr. Bloem for severe freezing of gait, and in his initial interview, mentioned he had ridden 15 miles the previous day.
“I said, ‘That's impossible!’” But the patient insisted he could ride, so they went outside and borrowed the bicycle of resident and first author Anke Snijders, MD.
“We put him on the bike, gave him a push, and off he went! I was as stunned as everybody else is when they see the video. It's just an amazing sight,” Dr. Bloem said. And this was no one-off trick. The patient rides every day, accompanied by his wife, who helps with mounting and dismounting.
THEORIES ABOUT GAIT
There are multiple hypotheses for how such fluid movements are possible in a patient plagued with freezing of gait. “I think this video is telling us a little about how the brain is organized,” Dr. Bloem said, and how it responds in PD.
One of the leading hypotheses about freezing of gait concerns the mechanics of walking. In order to swing one leg forward, weight must be shifted to the other. “That combination of movements may be specifically disturbed in PD,” Dr. Bloem said. “When you are on a bicycle, you don't have to do this with your feet.” Another factor may be the benefit from a rhythmic tactile cue provided by the pressure from the pedals. It is well known that freezing may respond to a variety of such cues, including from music or visual patterns on the floor.
“A third explanation may be that the whole motor program for cycling may be stored in a different part of the brain,” he said. Normally, the basal ganglia oversee such repetitive tasks as stride length, freeing up the cortex for other activities. Degeneration of that programmed routine may underlie freezing, “but apparently people with Parkinson disease are able to use other, intact, neural circuitries that are not primarily involved in generating motion, to tap into the same motor cortex, to bring about the same movements,” Dr. Bloem said.
Remarkably, this cycling skill is not confined to this one patient. Dr. Bloem has since interviewed 20 of his patients with freezing of gait, and all of them could still ride, though not all did so regularly, and some confined themselves to a fixed bicycle at home. He has also learned from other PD experts of similar such patients, including one in the Czech Republic filmed riding his mountain bike down the steps of a cathedral.
For John Nutt, MD, professor of neurology at the Oregon Health and Science University and director of the Parkinson Center of Oregon, what is most striking about this case is that “it shows us that there is something very special about gait in Parkinson disease,” which is severely impaired even though strength and the ability to coordinate the legs is still intact. “There appears to be some problem specifically with stepping.”
“No one has an absolute answer” to the question of what underlies the selective preservation of cycling in such PD patients, said Mark Hallett, MD, senior investigator in neuroscience at the NINDS and chief of the Human Motor Control Section in the Medical Neurology Branch. “But different motor programs may be run by the nervous system differently,” he said. “Bicycle riding is a different task from walking, and the amount of impairment could be independent of the problem with walking.”
Not much is known about the physiology of such task specificity, he added. “But it has always been clear that Parkinson disease patients are capable of much more than they actually do.” Patients “underscale” in many activities, accounting for the hypophonia, the smaller steps, and other motor features of the disease.
As for the clinical implications, Dr. Bloem is emphatically not recommending that all PD patients hop on their bicycles, and is not even ready to say that more exercise is better. There is a concern about increasing hip fractures or myocardial infarctions that must be balanced against the benefits of exercise, and Dr. Bloem is currently embarked on a large study to directly address the risks and benefits of vigorous exercise in this population.•