ENS 2009: Parkinson's Patients Have Reduced Pain Threshold

Allison Gandey

June 24, 2009

June 24, 2009 (Milan, Italy) — Patients with Parkinson's disease appear to have a lower threshold for pain and less tolerance, report researchers. Presenting here at the 19th Meeting of the European Neurological Society, investigators suggest that nociceptive information is altered in Parkinson's disease.

"This abnormality appears to be greater in the presence of muscular or neuropathic pain," lead author Sandro Zambito Marsala, MD, from San Martino Hospital, in Belluno, Italy, told Medscape Neurology.

Investigators studied 78 patients with Parkinson's disease. Of these, 28 had no pain, 29 patients had arthralgic pain, and 21 had muscular or neuropathic pain. Pain was present in 1 body part at the time of the study and had developed after the onset of Parkinson's motor symptoms.

The researchers excluded patients with headache or other facial pain, medical conditions associated with or predisposing to painful symptoms, cognitive impairment, and depression.

Altered Nociceptive Information

After an overnight withdrawal of all dopaminergic medications, investigators assessed pain threshold and tolerance. Testing involved delivering electrical stimulations to the little finger and big toe. Researchers evaluated both the right and left hand and foot of each patient. They then compared the results with those obtained in 45 aged-matched controls.

Dr. Sandro Zambito Marsala at the meeting.

"This is a very simple and reliable method that can be conducted in any hospital," said Dr. Zambito Marsala.

Investigators found that pain threshold and tolerance were significantly lower in patients with Parkinson's disease for both right and left hand and foot than healthy subjects. In Parkinson's patients with preexisting pain, the threshold and tolerance obtained from the painful limb were even lower.

The researchers suggest their findings extend previous data reporting nociceptive information is altered in Parkinson's disease. They point to a recent case-control study of a large number of subjects reporting a significant association between Parkinson's disease and nondystonic pain (Defazio G et al. Arch Neurol. 2008;65:1191-1194).

Dr. Zambito Marsala and his team also recently reported on abnormal pain-evoked responses to laser stimulation in Parkinson's patients. That study suggested alterations to nociceptive processing (Tinazzi M et al. Pain. 2008;136:117-124).

Asked by Medscape Neurology to comment, Sarah Grace Wesley, MD, from the Royal College of Surgeons in Dublin, Ireland, said this latest study has "great relevance for clinical practice." She applauded the work for its statistical significance and objective measures of pain.

It is, however, a small study, she adds, and will require further investigation in a larger sample. But she said, "It's a very good start."

The researchers have disclosed no relevant financial relationships.

19th Meeting of the European Neurological Society: Abstract P400. Presented June 23, 2009.

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