Patient Perception of Vocal Tremor Severity and its Relationship to Acoustic Voice Outcomes: An Exploratory Study

Vocal tremor profoundly impacts communication, social participation, and quality of life. Although expert auditory-perceptual ratings of vocal tremor severity align with acoustic voice outcomes (e.g., extent of frequency (f _o) and intensity modulation), patient perception of their voice remains unexamined despite its clinical importance. This study aimed to characterize the relationship between patient-reported vocal tremor severity and acoustic voice outcomes at baseline and after botulinum toxin injections.

Patients diagnosed with vocal tremor affecting multiple structures (ETvt) or tremor only observed in the larynx (LDvt) were recruited. Participants completed the voice section of the Quality of Life in Essential Tremor questionnaire to assess patient perception and performed sustained /ɑ/ at a comfortable pitch and volume, from which acoustic voice outcomes (rate and extent of fundamental frequency [f_o ] and amplitude [dB] modulation) were derived. A subset of participants received botulinum toxin injections and were reassessed within the therapeutic window (within 12 weeks).

Thirty participants (29 females; mean age = 72 years, SD = 11.40) were analyzed. Participants who rated their vocal tremor as "severe" demonstrated higher rate f_o (β = 1.20, 95% CI: -0.10, 2.60 Hz) and rate dB (β = 2.30, 95% CI: 0.50, 4.10 Hz) compared to participants who rated their tremor as "moderate". Participants who rated their tremor as "marked" demonstrated higher rate f_o (β = 1.50, 95% CI: 0.30, 2.60 Hz) compared to "moderate" ratings. Improvements in patient perception of vocal tremor and acoustic outcomes were highly heterogenous among seven participants who received botulinum toxin.

Participants reporting more severe vocal tremor demonstrated more aberrant acoustic voice outcomes. After botulinum toxin injection, substantial heterogeneity was observed in acoustic voice measures which varied based on patient perception of change. These preliminary, exploratory findings provide a foundation for future investigations to define meaningful change in this population.