Voice Quality Outcomes Of Idiopathic Parkinson'S Disease Medical Treatment: A Systematic Review

IntroductionTo investigate voice quality (VQ) impairments in idiopathic Parkinson's disease (IPD) and to explore the impact of medical treatments and L-Dopa challenge testing on voice.MethodsRelevant studies published between January 1980 and June 2017 describing VQ evaluations in IPD were retrieved using PubMed, Scopus, Biological Abstracts, BioMed Central and Cochrane databases. Issues of clinical relevance, including IPD treatment efficiency and voice quality outcomes, were evaluated for each study. The grade of recommendation for each publication was determined according to the Oxford Centre for Evidence-Based Medicine evidence levels.ResultsThe database research yielded 106 relevant publications, of which 33 studies met the inclusion criteria, for a total of 964 patients with IPD. Data were extracted by 3 independent physicians who identified 21, 11 and 1 trials with IIIb, IIb and IIa evidence levels, respectively. The main VQ assessment tools used were acoustic testing (N=27), aerodynamic testing (N=10), subjective measurements (N=8) and videolaryngostroboscopy (N=3). The majority of trials (N=32/33) identified subjective or objective VQ improvements after medical treatment (N=10) or better VQ evaluations in healthy subjects compared to patients with IPD (N=22). Especially, our analysis supports that VQ overall improves during the L-Dopa challenge testing, making the VQ evaluation an additional tool for the IPD diagnosis. The methodology used to assess subjective and objective VQ substantially varied from 1 study to another. All of the included studies took into consideration the patient's clinical profile in the VQ analysis.ConclusionThe majority of studies supported that VQ assessments remain useful as outcome measures of the effectiveness of medical treatment and could be helpful for the IPD diagnosis based on L-Dopa challenge testing. Further controlled studies using standardised and transparent methodology for measuring acoustic parameters are necessary to confirm the place of each tool in both IPD diagnosis and treatment evaluation.