Voice Quality and Orofacial Strength as Outcome of Levodopa Effectiveness in Patients with Early Idiopathic Parkinson Disease: A Preliminary Report

Abstract

Sixty to 90% of patients with idiopathic Parkinson disease (IPD) developed early dysphonia and subtle speech impairment, which is usually related to orofacial muscular dysfunctions. The aim of this preliminary study is to assess the usefulness of voice quality and orofacial strength (involved in speech) as outcome of levodopa challenge test used for the IPD diagnosis. A total of 20 patients with early IPD were recruited and evaluated for clinical findings (Hoehn and Yahr scale), voice handicap index, maximal phonation time, phonation quotient, percent jitter, percent shimmer, noise-to-harmonic ratio, and orofacial muscular strength (Iowa Oral Performance Instrument) at baseline, throughout the levodopa challenge test and after therapeutic stabilization. The intake of a standardized dose of levodopa (levodopa challenge test) significantly improved phonation quotient and percent shimmer. We did not find similar improvement after medical stabilization of patients (based on levodopa medication) despite an improvement of Hoehn and Yahr mean score. The intake of levodopa significantly improved cheeks and lips strength involved in speech quality both along the challenge test and after the therapeutic stabilization. These preliminary findings support a differential impact of levodopa on voice and speech functions in early diagnosed IPD and a mismatch between the clinical examination, orofacial strength, and voice quality improvements once the patient is medically stabilized.