Clinical Features of Essential Voice Tremor and Associations with Tremor Severity and Response to Octanoic Acid Treatment.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to characterize the clinical features, tremor variability, and factors related to octanoic acid (OA) treatment response in essential voice tremor (EVT). STUDY DESIGN: Prospective, double blind, placebo-controlled, crossover study with secondary analysis. METHODS: Clinical tremor features in 16 individuals with EVT were comprehensively assessed, and correlations with acoustic tremor severity were determined. Intrasubject and intersubject variability measures were analyzed from 18 repeated measures for each acoustic tremor variable. Clinical correlates of treatment response were evaluated, and cumulative effects over a 2-week period of OA drug dosing were assessed. RESULTS: Participants with EVT were 90% female with a mean age of 70.31 (±8.68) years at the time of testing. Neurologist-rated body tremor beyond the vocal tract region was present in 69% of participants, and multiple vocal tract regions contributed to the voice tremor. The mean frequency of amplitude tremor was 4.67 Hz (±0.88). Respiratory tremor was evident in 50% of participants. Participants experienced moderate voice-related disability as assessed on the Voice Handicap Index-10 (19.38, ±8.50), and increased speaking effort. Acoustic tremor severity was significantly associated with severity of tremor affecting vocal tract structures. Overall intrasubject consistency was strong (single measures intraclass correlation coefficient = 0.701, P < .01), with high intersubject variability. Acoustic tremor severity was significantly, positively associated with treatment response, and results suggested a cumulative OA benefit for magnitude of amplitude tremor. CONCLUSIONS: This study identified common clinical correlates of EVT and demonstrated positive associations between acoustic tremor severity, severity of affected vocal tract structures, and response to treatment. LEVEL OF EVIDENCE: 2 Laryngoscope, 131:E2792-E2801, 2021.

The effect of anchors on reliability of endoscopic tremor ratings.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to determine the effects of anchors and training on intrarater and inter-rater reliability for visual-perceptual, endoscopic tremor ratings. STUDY DESIGN: Prospective cohort study. METHODS: Nasoendoscopy recordings of 10 participants with a diagnosis of essential voice tremor were evaluated by five voice specialists using the Vocal Tremor Scoring System. Ratings were performed before, immediately after, and 4 weeks after implementation of a training program with anchor stimuli. Immediate and long-term post-training ratings were performed with simultaneous use of anchor samples for each rating. RESULTS: Intrarater reliability showed significant improvement from pretraining to immediate and long-term post-training. Mean correlation coefficients (Spearman's rho) increased from 0.71 at pretraining to 0.84 and 0.90 at immediate and long-term post-training, respectively. Inter-rater reliability was not affected by training with anchors, with mean correlation coefficients ranging from 0.62 at pretraining to 0.58 and 0.64 at immediate and long-term post-training, respectively. CONCLUSIONS: Consistent, reproducible ratings are critical for the interpretation and comparison of endoscopic tremor data. Reliability findings from this study indicate that the use of anchor samples as referents for making ordinal judgments about the severity of tremor in oropharyngeal and laryngeal regions was helpful for improving internal standards and consistency but less useful for calibrating across different raters. LEVEL OF EVIDENCE: 4 Laryngoscope, 2016 127:411-416, 2017.

A Preliminary Quantitative Comparison of Vibratory Amplitude Using Rigid and Flexible Stroboscopic Assessment.

STUDY OBJECTIVE: The purpose of this study was to establish preliminary, quantitative data on amplitude of vibration during stroboscopic assessment in healthy speakers with normal voice characteristics. Amplitude of vocal fold vibration is a core physiological parameter used in diagnosing voice disorders, yet quantitative data are lacking to guide the determination of what constitutes normal vibratory amplitude. METHODS/STUDY DESIGN: Eleven participants were assessed during sustained vowel production using rigid and flexible endoscopy with stroboscopy. Still images were extracted from digital recordings of a sustained /i/ produced at a comfortable pitch and loudness, with F0 controlled so that levels were within ±15% of each participant's comfortable mean level as determined from connected speech. Glottal width (GW), true vocal fold (TVF) length, and TVF width were measured from still frames representing the maximum open phase of the vibratory cycle. To control for anatomic and magnification differences across participants, GW was normalized to TVF length. GW as a ratio of TVF width was also computed for comparison with prior studies. RESULTS: Mean values and standard deviations were computed for the normalized measures. Paired t tests showed no significant differences between rigid and flexible endoscopy methods. Interrater and intrarater reliability values for raw measurements were found to be high (0.89-0.99). CONCLUSIONS: These preliminary quantitative data may be helpful in determining normality or abnormality of vocal fold vibration. Results indicate that quantified amplitude of vibration is similar between endoscopic methods, a clinically relevant finding for individuals performing and interpreting stroboscopic assessments.