Anticholinergic-induced analgesia: possible role for the cholinergic system in abnormal sensory symptoms in Parkinson's disease.

Sensory symptoms related to pain perception have been reported to occur in 30-50% of parkinsonian patients. Two patients with Parkinson's disease are reported, in whom painful sensory phenomena preceded or accompanied the disease process. In both patients the sensory phenomena were unresponsive to therapy with oral narcotics, anti-inflammatory drugs or administration of levodopa/carbidopa. Benzhexol (4-6 mg/day) produced dramatic amelioration of symptoms, indicating a role for the cholinergic system in the pathophysiology of abnormal sensory symptoms in Parkinson's disease and possibly in human analgesia in general.