Effects of Levodopa on Vowel Articulation in Patients with Parkinson’s Disease

摘要

Objectives. The effects of levodopa on articulatory dysfunction in patients with Parkinson's disease remain inconclusive. This study aimed to investigate the effects of levodopa on isolated vow el articulation and motor performance in patients with moderate to severe Parkinson's disease, excluding speech fluctuations caused by dyskinesia. Methods. 21 patients (14 males and 7 females) and 21 age- and sex- matched healthy subjects were enrolled. Together w ith motor assessment, the patients phonated five Japanese isolated vow els (/a/, /i/, /u/, /e/, and /o/) 20 times before and 1 h after levodopa treatment. We made the frequency analysis of each vowel and measured the first and second forma nts. From these formants w e co nstructed the pentagonal vo wel space area w hich should be the good indicator for articulatory dysfunction of vowels. In control subjects, only speech sa mples were analyzed. To investigate the sequential relationship between plasma levodopa concentrations, motor performances, and acoustic mea surements after treatment, entire drug cycle tests were performed in 4 patients. Results. The pentagonal vowel space area was significantly expanded together with motor amelioration after levodopa treatment, although the enlargement is not enough for the space area of control subjects. Drug cycle tests revealed that sequential increases or decreases in plasma levodopa levels after treatment correlated well with expansion or decrease of the vowel space areas and improvement or deterioration of motor manifestations. Conclusions. Levodopa expanded the vowel space area and ameliorated motor performance, suggesting that dysfunctions in vowel articulation and motor performance in patients with Parkinson's disease are based on dopaminergic pathology.