The epidemiology of pain in Parkinson's disease.

Pain occurring in Parkinson's disease (PD) may affect a large proportion of patients. Based on the results of the methodologically more robust case-control studies that detected a significantly greater frequency of pain in PD patients than in control subjects, pain should now be considered as a non-motor symptom of PD. The heterogeneous quality of pain, the variable relationship of pain with parkinsonian motor signs, and the mixed response of pain to dopaminergic drugs suggest complex mechanisms for pain in PD. Some evidence raises the possibility of common mechanisms shared by pain patients, regardless of the clinical heterogeneity of pain and its variable relationship with motor signs.