Chronic pain in Parkinson's disease: Clinical and pathophysiological aspects.

Pain is an increasingly recognized non-motor symptom of Parkinson's disease (PD), with significant prevalence and strong impact on quality of life of patients. Moreover, pain can occur with various features in PD and several subtypes may coexist in a same patient, leading to a complex presentation and difficult diagnosis and treatment. In this paper we review the clinical manifestations of painful phenomena in PD, with focus on classifications and algorithms allowing to standardize the diagnosis of pain and PD. We also discuss the pathophysiological mechanisms underlying pain in PD, particularly parkinsonian central pain, in regard to recent clinical, neurophysiological and imaging studies.