Voice disturbances in Parkinson's disease and essential tremor: A cross-sectional acoustic comparison

Dysphonia is frequent in Parkinson's disease (PD) and essential tremor (ET), the most prevalent movement disorder entities. Direct comparisons of acoustic speech features between them are scarce. This study aimed to establish an objective basis for distinguishing these forms of pathological speech.

We performed an observational cross-sectional study with 33 PD patients, 32 ET patients, and 38 healthy controls (HC). We assessed subjective voice impairment using the Voice Handicap Index (VHI) and objective voice parameters with a sustained phonation vocal task. Clinical severity was evaluated using established scales.

Compared to HC, ET patients exhibited higher jitter, shimmer and modulation depth of frequency tremor. And lower harmonics-to-noise ratio. PD patients showed higher shimmer and lower first spectral moment of mean long-term average spectra, cepstral peak prominence, and harmonics-to-noise ratio. In the comparison between patients, ET subjects had higher modulation depth of frequency tremor than PD. PD and ET patients scored higher than HC in total VHI and its subscores. Functional subscore was higher in PD than in ET. Significant correlations were found between acoustic parameters and VHI, especially in the ET group, with the strongest correlation for LTAS first spectral moment with VHI-emotional (r = 0.56,P = 0.002).

While ET and PD patients overlap in acoustic voice abnormalities that affect voice quality, a higher extent of frequency tremor was distinctive for ET. Both cohorts reported a higher subjective impact of voice tremor in comparison with HC. Acoustic parameters seemed to align more with patient reported outcomes in ET than in PD.