Pain Is Symptom of Parkinson's Disease

By Michael Smith
BARI, Italy, 09 sept 2008 -- Pain should be considered as a non-motor symptom of Parkinson's disease, researchers here said.
In a multi-center case-control study, volunteers with Parkinson's experienced pain more often than did age-matched controls, mainly because of the frequency of pain associated with dystonia, according to Giovanni Defazio, M.D., Ph.D., of the University of Bari, and colleagues.
But although the frequency of non-dystonic pain was similar between the cohorts, it was significantly associated in the Parkinson's cases with the clinical onset of disease, they said in the September issue of Archives of Neurology.
The findings "support the hypothesis that pain begins at clinical onset of Parkinson's disease or thereafter as a non-motor feature of Parkinson's disease," Dr. Defazio and colleagues concluded.
The study may also have implications for understanding "pain mechanisms in Parkinson's disease and identifying specific treatment strategies," the researchers said.
They looked at pain in 402 volunteers with Parkinson's disease selected from consecutive outpatients at participating centers from Nov. 1, 2006 through March 31, 2007, and compared such variables as frequency, type, and location with 317 healthy controls.
The cohorts were similar with respect to age, sex, and years of schooling, but significantly more Parkinson's patients had depression (16.7% versus 6%, significant at P=0.001) and medical conditions associated with painful symptoms (24.6% versus 35.3%, significant at P=0.02).
The researchers found:
More patients than controls reported experiencing pain for at least three months (69.9% versus 62.8%, significant at P=0.04).
Pain associated with visible dystonia was more frequent among patients than controls (6.7% versus 0%, significant at P<0.001).
Non-dystonic pain was reported with comparable frequency by case and control subjects (66.4% versus 62.8%).
However, when the researchers considered those without pain as a reference group and asked if the pain appeared before or after a reference age, they found a significant association between Parkinson's and non-dsytonic pain arising after the reference age.
In the case of patients, the reference age was the year of onset of symptoms. It was obtained for controls by subtracting the average disease duration of case patients included in the corresponding age stratum from the age of the control.
Specifically, the analysis showed:
There was no difference between patients and controls if the pain appeared before the reference age.
Pain appeared after the reference age twice as often in patients as in controls. The odds ratio was 2.1, with a 95% confidence interval from 1.4 to 2.9, which was significant at P<0.001.
Patients were more likely to have pain from cramping and central neuropathic pain. (The odds ratios were 2.5 and 2.9, significant at P=0.005 and P=0.04.)
There was little difference in arthalgic or peripheral neuropathic pain.
Patients were more likely to have pain in the shoulder, back, leg or foot.
The researchers did not report any external support for the study, nor any disclosures.
Primary source: Archives of NeurologySource reference:Defazio G, et al "Pain as a Nonmotor Symptom of Parkinson Disease: Evidence From a Case-Control Study" Arch Neurol 2008; 65(9): 1191-1194.