Short- and long-term dopaminergic effects on dysarthria in early Parkinson's disease

While the beneficial effect of levodopa on motor impairment in Parkinson's disease (PD) has been well documented, its effect on speech has rarely been examined and the respective literature is inconclusive. The aim of our study was to analyze the effect of short-term levodopa admission and long-term dopaminergic treatment on speech in PD patients in early stages of the disease. Motor examination according to UPDRS III and speech testing were performed in 23 PD patients (9 males; median age 68, 42-78 years) in the early morning after having abstained from dopaminergic medication overnight ("off" state, t0) after administration of 200 mg of soluble levodopa (t1), and at follow-up after 12-14 weeks under stable dopaminergic medication (t2). Speech examination comprised the perceptual rating of global speech performance and an acoustical analysis based upon a standardized reading task. While UPDRS III showed a significant amelioration after l-dopa application, none of the parameters of phonation, intonation, articulation and speech velocity improved significantly in the "on" state, neither under short-term levodopa administration (t1) nor on stable dopaminergic treatment (t2). However, there was a positive effect of dopaminergic stimulation on vowel articulation in individual patients. Results indicated significant beneficial effect of short-term levodopa administration or long-term dopaminergic medication on different dimensions of speech in PD patients. As some improvement of vowel articulation was seen in individual patients, the pre-existing pattern of speech impairment might be responsible for the different response to pharmacological treatment.