Among the different types of pain observed in Parkinson's disease, primary parkinsonian pain (PPP) is the most severe, the most difficult to treat, but also the least well characterized and the hardest to describe, not only by patients but also by neurologists. Consequently, PPP remains difficult to identify, even for clinicians with expertise in Parkinson's disease.

Nevertheless, patients with Parkinson's disease who experience PPP appear to exhibit certain demographic and clinical characteristics that may help distinguish them from other patients, including a poorer motor response to levodopa, a stronger association with sleep disturbances, and cognitive and behavioral features such as impulse control disorders (ICDs). PPP may therefore be associated with a specific disease phenotype supported by distinct pathophysiological mechanisms.

Recently, a disease progression model proposed the existence of a "Brain-First" subtype (characterized by disease onset in the brainstem) and a "Body-First" subtype (characterized by disease onset in the gastrointestinal system). Several clinical markers appear to distinguish these subtypes, notably the presence of REM sleep behavior disorder (RBD), which has been associated with the Body-First phenotype.

The association between PPP and RBD, as well as between PPP and the Body-First subtype, has never been investigated. We hypothesize that PPP may be associated with several clinical markers of the Body-First phenotype. Identifying such associations could facilitate the routine clinical diagnosis of PPP and, consequently, improve its management, which remains inadequate at present.

The primary objective is to assess the proportion of patients with primary parkinsonian pain according to the presence of probable RBD in Parkinson's disease.

This prospective, cross-sectional, non-interventional category 3 study (RIPH 3) will be conducted in 300 patients. Patients contacted through the France Parkinson Association and interested in participating in the study will be able to access the online questionnaire via a QR code or a web link. Completion of the questionnaire is expected to take no more than 15 minutes. This self-administered questionnaire will include collection of general data (age, sex, disease duration, initial motor symptoms, side of symptom onset predominance, and comorbidities), assessments of pain, migraine, sleep, constipation, olfaction, anxiety and depression and impulse control disorders.

Inclusion Criteria:

• Age ≥ 18 years.
• French-speaking.
• Diagnosis of Parkinson's disease confirmed by a neurologist.

Exclusion Criteria:

• Atypical parkinsonian syndrome.
• Patients under legal protection (guardianship, curatorship, or legal safeguard measures).

Patients will be contacted through the France Parkinson Association. If interested in the study, they will be able to access the online questionnaire hosted on the REDCap platform via a QR code or a web link.