Pain in Parkinson disease: A review of the literature

Abstract

Parkinson's disease (PD) is a degenerative neurological disease presenting with motor and non-motor signs and symptoms. Approximately 30-50% of the patients experience pain. There is no consensus regarding the mechanisms and classification of pain in PD. This paper reviews current data on the possible mechanisms, classifications, evaluation and potential risk factors for pain in PD. Literature searches were performed to identify clinical trials and reviews covering patho-physiology, classification, type, evaluation and risk factors associated with pain in PD. Pain in PD could be related to pathologic changes in the anatomic structures involved in nociceptive mechanisms. Studies on pain mechanisms have been mostly conducted in animals. The mechanism of pain is complicated and influenced by different factors. There are several methodological differences between the studies trying to classify pain and to characterize its subtypes. Potential risk factors for pain in PD include: age, gender, and duration of the disease. Although pain is one of the non-motor symptoms most frequency experienced by patients, it is often under recognized and inadequately treated in contrast to motor symptoms Multicenter studies are needed that include a large cohort of subjects evaluated in multiple dimensions including pain in order to obtain more data and to allow improved management of pain in patients with PD.

Pain perception in Parkinson’s disease: A systematic review and meta-analysis of experimental studies

“…These variables were examined to provide preliminary data on any potential moderating influence, as all have been suggested as possible influences [19]. Additionally, meaningful study validity criteria were assessed as moderators, such as case and control selection, criteria-based PD diagnosis, explicit mentioning of disallowing pain medications.…”

“…Pain often appears early in the development of PD and may be present years before clinical diagnosis [49]. Pain has been rated as the most burdensome non-motor symptom [7], and contributes to PD-related disability, sleep disturbance, and impaired quality of life [9,19,46]. Non-motor symptoms including pain are also a frequent cause of hospitalisation and institutionalisation of PD patients and can increase healthcare costs by up to four times [9].…”

“…While pain in PD is often precipitated by muscular rigidity and/or postural abnormalities [22], neurodegenerative processes could potentially affect not only motor function, but also peripheral [43] and brain [19] pathways involved in pain processing. For example, degradation of dopamine-producing cells in the substantia nigra may impair natural analgesia by disrupting the dopamine-mediated descending pathways that block transmission of ascending nociceptive signals from the spinal cord [19].…”

“…For example, degradation of dopamine-producing cells in the substantia nigra may impair natural analgesia by disrupting the dopamine-mediated descending pathways that block transmission of ascending nociceptive signals from the spinal cord [19]. A role of dopamine in pain is consistent with reduced pain sensitivity seen in schizophrenia [53], a disorder linked to dopamine dysregulation, and the possible partial restoration of normal pain thresholds in PD during functional ON states following treatment with dopaminergic agents [13].…”

“…While several studies have found increased pain sensitivity in PD patients compared to healthy controls (HCs) in response to noxious experimental stimulation [10,32,39], others have failed to find such an effect [25,35,61]. This inconsistency may be influenced by methodological differences across studies, including variation in sample size, dopaminergic and analgesic medications, disease duration and symptom severity [19,45].…”