Impact of Vagal Nerve Stimulation on Objective Vocal Quality, a Pilot Study

The purpose of this study was to determine the impact of vagal nerve stimulation (VNS) on the vocal quality using the dysphonia severity index (DSI). It was hypothesized that the objective vocal quality and other vocal characteristics are disordered in comparison with an age- and gender-matched control group. In addition, the acoustic vocal parameters were compared during three conditions: at rest, during normal stimulation, and raised stimulation. A significant relation between the amount of stimulation and the presence of disturbed acoustic parameters was hypothesized.

Subjective (auditory-perceptual evaluation and voice handicap index) and objective (aerodynamic, vocal range, acoustic measurements and determination of the DSI) measurements were used to determine the vocal quality in 13 subjects with VNS in three different conditions (at rest and during normal and raised stimulation) and the age- and gender-matched control group.

The subjects with VNS had a disordered perceptual vocal quality mainly characterized by the presence of a moderate roughness and slight breathiness, and the objective vocal quality by means of the DSI value is -2.4. During stimulation and especially during raised stimulation, the fundamental frequency is significantly increased. However, the subjects experienced no psychosocial handicapping effect of the vocal quality on the quality of life.

Subjects with VNS have typical vocal characteristics. Ear, nose, and throat specialists and voice therapist must be aware of the presence of this vocal pattern at rest and during normal and raised stimulation. Especially, professional voice users and elite vocal performers must be informed before implantation.