Glottographic measures before and after levodopa treatment in Parkinson's disease

Objectives: Investigate the usefulness of acoustic and glottographic measur es for detecting effects of levodopa (L-dopa) treatment on vocal function o f individuals with idiopathic Parkinson's disease. Study Design: Compare re cordings of vowels sustained at a target comfortable loudness level obtaine d before and after L-dopa treatment from 15 individuals with idiopathic Par kinson's disease showing signs of tremor. Methods: A simultaneous acoustic, airflow, and electroglottographic recording technique was employed to reco rd vowels phonated by subjects before and after L-dopa treatment. Algorithm s were developed to derive from the recorded signal measures of fundamental frequency, SPL, airflow rate, speed quotient (ratio of glottal opening to closing time time), and short- and long-term phonatory instability, A serie s of paired Student t tests or signed rank tests were performed to compare the pretreatment and posttreatment groups on these measures. Results: Measu res of speed quotient, acoustic shimmer (cycle-to-cycle amplitude perturbat ion), and the extent of tremor derived from acoustic intensity contours wer e found to significantly decrease after medication. Sound pressure level te nded to increase after medication, The acoustic jitter (cycle-to-cycle freq uency perturbation) and the extent of tremor derived from airflow signals d id not significantly differentiate between premedication and postmedication voices. Conclusions: Objective measures of acoustic and electroglottograph ic signals are useful in monitoring the pharmacologic response of Parkinson 's disease, reflecting decrease of laryngeal rigidity and short- and long-t erm acoustic amplitude fluctuation after L-dopa treatment.