Differentiation of Parkinson's disease from atypical parkinsonism is important clinically, for adequate patient counselling, and scientifically, to ascertain proper inclusion in clinical trials. The differential diagnosis remains challenging, even with current clinical insights and modern ancillary investigations.1 Here, we suggest that the answer to one simple question—“Can you still ride a bicycle?”—offers good diagnostic value for separating Parkinson's disease from atypical parkinsonism.
We did a prospective observational study in 156 consecutive patients with parkinsonism, but without a definitive diagnosis. At baseline, patients received a structured interview, comprehensive neurological assessment, and cerebral MRI. The interview included a standard question about whether, when, and why cycling had become impossible. The gold standard was the diagnosis after 3 years, which was based on the clinical follow-up including repeat neurological examination, response to treatment, and MRI. All assessments were done by a single, experienced examiner. All patients gave informed consent, as approved by the local ethics committee.
Before their first disease manifestation, 111 patients rode a bicycle (table). 45 went on to develop a gold-standard diagnosis of Parkinson's disease and 64 a form of atypical parkinsonism. At the time of inclusion (median disease duration 30 months), 34 of the 64 patients with atypical parkinsonism had stopped cycling, as opposed to only two of the 45 patients with Parkinson's disease (sensitivity 52%, specificity 96%; AUC 0·74, 95% CI 0·64—0·83). The loss of cycling abilities was present for all forms of atypical parkinsonism. Regression analysis revealed no significant effect of age, parkinsonism, or ataxia on the ability to cycle, suggesting that this was an independent marker of atypical parkinsonism.
