'Bicycle Sign' May Distinguish Parkinson's From Atypical Parkinsonism

Susan Jeffrey

January 07, 2011

January 7, 2011 — New research suggests the preserved ability to ride a bicycle after onset of symptoms may accurately differentiate between Parkinson's disease (PD) and atypical parkinsonism.

The investigators, with senior study author Bastiaan R. Bloem, MD, PhD, medical director of the Parkinson Center Nijmegen at Radboud University Nijmegen Medical Center, the Netherlands, had previously reported a case study of a patient with advanced PD who showed an astonishing residual ability to ride a bicycle.

Now they have found in a new series of patients that preserved cycling ability is limited to patients with PD but is already lost early after disease onset among those with atypical parkinsonism.

"Simply asking about cycling abilities could be added to the list of red flags that can assist clinicians in their early differential diagnosis of parkinsonism," the study authors conclude.

"Importantly, this simple question turned out to have better diagnostic value than a combined set of expensive and partially invasive ancillary examinations: MRI [magnetic resonance imaging] scan of the brain, nuclear brain imaging, electromyography, and a spinal tap," Dr, Bloem told Medscape Medical News. "The simple question about cycling can thus help to save money, while reducing the burden for patients."

They report their findings as correspondence in the January 8 issue of The Lancet.

Asked for comment on these findings, Marc Y. Wasserman, MD, a neurologist at Phoenix Neurology and Sleep Medicine in Litchfield Park, Arizona, and a member of the American Academy of Neurology called this a "wonderful observation."

"The ability to ask a simple question that can help with differentiation of a complex neurological disorder is always helpful, and this is a delightful, simple observation that genuinely helps with diagnosis," he told Medscape Medical News.

Freezing of Gait

In April 2010, Dr. Bloem and colleague Anke Snijders, MD, reported the case of a 58-year-old man with advanced PD and severe freezing of gait who could nonetheless ride his bicycle for up to 15 miles per day. After meeting this patient, Professor Bloem reported having found an additional 20 PD patients in his outpatient clinic, where he specializes in gait and balance disorders, all of whom could still ride a bicycle (N Engl J Med. 2010;362:13).

"In hindsight, it's not a unique observation, and we've just missed out, maybe because we failed to ask about it or patients fail to volunteer this, but it's certainly not a unique observation," he told Medscape Medical News at that time.

Making the differential diagnosis between PD and atypical parkinsonism disorders, such as progressive supranuclear palsy, multiple system atrophy, or Lewy body dementia, is important clinically for counseling patients and accurate inclusion of suitable patients into trials but remains challenging, they note.

"Here, we suggest that the answer to 1 simple question — 'Can you still ride a bicycle?" — offers good diagnostic value for separating Parkinson's disease from atypical parkinsonism," they write.

To look at this prospectively, investigators performed an observational study of 156 consecutive patients who presented with parkinsonism but did not yet have a definitive diagnosis. All had a structured interview, comprehensive neurological assessment, and cerebral MRI, nuclear brain imaging, electromyography, and lumbar puncture at baseline. Standard questions in the interview asked "whether, when, and why" cycling had become impossible for them.

The gold standard for diagnosis was at 3 years of follow-up, based on clinical examination, response to treatment, and MRI.

Of these patients, 111 had ridden a bicycle before first manifestation of their disease; 45 developed PD and 64 some form of atypical parkinsonism, mostly multiple system atrophy (n = 35, 31.5%) or vascular parkinsonism (n = 17, 15.3%).

At the time of inclusion in the study, occurring at a median disease duration of about 30 months, 34 of 64 patients ultimately diagnosed as having atypical parkinsonism had stopped cycling compared with only 2 of the 45 PD patients, yielding a sensitivity of 52%, and a specificity of 96% (area under the curve, 0.74; 95% confidence interval, 0.64 – 0.83).

The loss of cycling ability was seen with all atypical parkinsonism conditions, they note, and regression analysis showed no significant effect of age, parkinsonism, or ataxia on this ability, "suggesting this was an independent marker of atypical parkinsonism," they write.

Cycling requires a highly coordinated interplay among balance, coordination, and rhythmic pedaling of the legs, Dr. Bloem and colleagues point out. "This skilled task is probably sensitive to subtle problems with balance or coordination, caused by the more extensive extranigral pathology in atypical parkinsonism," they speculate.

"We suggest that loss of the ability to cycle after disease onset might serve as a new red flag, signaling the presence of atypical parkinsonism," the study authors conclude. "The diagnostic value of the 'bicycle sign' was good: its presence was highly specific for the diagnosis of atypical parkinsonism."

The study was supported by a research grant from the Internationaal Parkinson Fonds. The study authors have disclosed no relevant financial relationships.

Lancet. 2011;377:125-126.