Quantitative measurement of pain sensation in patients with Parkinson disease

Pain is common in patients with Parkinson disease (PD) and can precede the diagnosis of the disease. Experimental studies and clinical evidence indicate involvement of basal ganglia and dopaminergic pathways in central pain processing. To quantitatively assess and compare pain perception in patients with unilateral PD with and without pain and in patients with response fluctuations. Thirty-six patients with PD (mean age, 61.8 +/- 11.2 years) with predominantly unilateral disease, 15 patients with response fluctuations (mean age, 65.3 +/- 10.4 years), and 28 age-matched healthy control subjects participated in the study. Subjective pain was assessed using the visual analog scale with von Frey filaments for tactile thresholds and contact thermode for warm sensation (WS) and heat pain thresholds (HPTs). Tactile and WS thresholds did not differ between patients in both patient groups and control subjects nor between sides. HPT was lower in patients with PD who experienced pain (n = 21) compared with those who did not (42.6 +/- 3.0 degrees C vs 45.6 +/- 2.8 degrees C; p < 0.01) and those who experienced pain in the more affected side (41.4 +/- 2.6 degrees C vs 43.7 +/- 3.3 degrees C; p < 0.0001). In patients with fluctuations there were no side differences in WS and HPT or between "on" and "off" periods. Endogenous pain in patients with Parkinson disease is accompanied by increased sensitivity to some painful stimuli, suggesting that basal ganglia abnormality also involves pain encoding.