L-Dopa decreases cutaneous nociceptive inhibition of motor activity in Parkinson's disease

OBJECTIVES: To estimate changes in motor inhibitory mechanisms at the spinal level in Parkinson's disease (PD) patients by measuring cutaneous silent responses to nociceptive stimuli in the course of L-Dopa therapy. MATERIALS AND METHODS: Fourteen patients with idiopathic PD (Group 1) and 13 patients with other forms of parkinsonism (Group 2) participated in the study. The cutaneous silent period (CSP) from the hand and clinical scores (UPDRS, part III) were measured "off" therapy (T0), after a single dose of L-Dopa (T1) and 3 months after the beginning of L-Dopa daily therapy (T2). RESULTS: At T0 the duration of the CSP was significantly prolonged in Group 1 and Group 2. At T1 and T2 the mean duration of the CSP significantly decreased in Group 1 (P < 0.05) and a significant correlation was found between the shortening of the CSP and the improvement of rigidity and bradikynesia in the upper limb. CONCLUSIONS: Our findings show that L-Dopa decreases the cutaneous nociceptive inhibition of motor activity in PD patients. CSP may be useful to assess L-Dopa responsiveness during the clinical course of PD.