Characterizing the Normative Voice Tremor Frequency in Essential Vocal Tremor | Laryngology | JAMA Otolaryngology–Head & Neck Surgery | JAMA Network
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Original Investigation
December 2018

Characterizing the Normative Voice Tremor Frequency in Essential Vocal Tremor

Author Affiliations
  • 1Division of Otolaryngology, Department of Surgery, Duke University, Durham, North Carolina
  • 2Department of Otolaryngology, The University of Alabama at Birmingham
  • 3currently an undergraduate student at Vanderbilt University, Nashville, Tennessee
  • 4Department of Otolaryngology, Vanderbilt University Medical Center, Vanderbilt University, Nashville, Tennessee
  • 5Division of Otolaryngology, Department of Surgery, Wisconsin Surgical Outcomes Research Program, University of Wisconsin–Madison
JAMA Otolaryngol Head Neck Surg. 2018;144(12):1169-1173. doi:10.1001/jamaoto.2018.2566
Key Points

Question  What is the normative frequency range in essential vocal tremor?

Findings  In a cross-sectional observational study, the normative frequency of essential vocal tremor in 160 participants was 3.8 to 5.5 Hz. Small within-patient differences (range, 0.1-0.5 Hz) were not clinically meaningful.

Meaning  The frequency of essential vocal tremor is narrow. The results of this study may better characterize this disease and its pathophysiology and assist in differential diagnosis.

Abstract

Importance  Essential vocal tremor (EVT) is a neurologic voice disorder characterized by periodic fluctuations in pitch and loudness that can hinder intelligibility. Defining the normative range of vocal tremor frequency may assist in diagnosis and provide insight into disease mechanisms.

Objective  To characterize the normative voice tremor frequency in EVT (in hertz).

Design, Setting, and Participants  Cross-sectional observational study of 160 patients with EVT. The setting was a tertiary voice center. Participants were identified from a database of consecutive patients diagnosed as having laryngeal movement disorders between January 1, 1990, and April 1, 2017.

Main Outcomes and Measures  The following 3 methods measured the frequency of tremor experienced by patients with EVT: perceptual method, computerized peak detection method, and laryngeal electromyography method. Within-person and population-level tremor frequencies were compared across modalities to assess measurement reliability and consistency and to characterize the normal distribution of tremor frequencies in this population.

Results  Among 160 participants (median age, 70 years; interquartile range [IQR], 64-77 years; 90.6% female [n = 145]), the median frequency of EVT was consistently between 4 and 5 Hz across all 3 methods (perceptual, 4.8 Hz [IQR, 4.4-5.5 Hz]; computerized peak detection, 4.6 Hz [IQR, 4.2-5.0 Hz]; and laryngeal electromyography, 4.3 Hz [IQR, 3.8-5.0 Hz]). The mean in-person differences between each measurement method were not clinically meaningful (range, 0.1-0.5 Hz). Including all interquartile ranges across measurement modalities, the normative tremor frequency range for EVT was 3.8 to 5.5 Hz.

Conclusions and Relevance  To our knowledge, this is the largest study to date to characterize the normal frequency of tremor in patients with EVT. The normative frequency of EVT (range, 3.8-5.5 Hz) falls within a much narrower range than previously reported. Those whose frequency is outside this range may still have EVT but should be carefully evaluated for potential other causes of vocal tremor. Defining characteristics of EVT may aid appropriate diagnosis and improve understanding of this disease.

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