De forma prospectiva, los investigadores realizaron un estudio observacional de 156 pacientes que presentaban parkinsonismo, pero que aún no tenían un diagnóstico definitivo. A todos se les realizó una entrevista estructurada, una evaluación neurológica completa y una resonancia magnética cerebral al inicio del estudio. Una de las preguntas estándar en la entrevista fue cuándo y por qué el ciclismo se había convertido en imposible para ellos.
De los 111 pacientes que habían montado una bicicleta antes de la primera manifestación de su enfermedad, 45 desarrollaron EP y 64 alguna forma de parkinsonismo atípico, sobre todo atrofia sistémica múltiple o parkinsonismo vascular. De los 64 pacientes diagnosticados de parkinsonismo atípico, 34 habían dejado el ciclismo en comparación con sólo 2 de los 45 pacientes con EP.
The “bicycle sign” for atypical parkinsonism
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.
Table
We suggest that loss of the ability to cycle after disease onset might serve as a new red flag, signalling the presence of atypical parkinsonism. The diagnostic value of the “bicycle sign” was good: its presence was highly specific for the diagnosis of atypical parkinsonism. This observation does not stand alone. Patients with Parkinson's disease have few balance problems moving sideways,2 their gait is typically narrow-based,3 their tandem gait is usually normal,4 and they can show a remarkable ability to ride a bicycle.5 Cycling requires a highly coordinated interplay between balance, coordination, and rhythmic pedalling of the legs. This skilled task is probably sensitive to subtle problems with balance or coordination, caused by the more extensive extranigral pathology in 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.
This work was supported financially by a research grant from the Internationaal Parkinson Fonds. We declare that we have no conflicts of interest.
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