HSC Section 6 Nov2016 Green Book

Akihito Yamauchi, et al

HSDI Analysis of VFA

vocal fold scar or sulcus vocalis) will be called for in the near future to further validate its utility. The study design in which the HSDI study and acoustic or aerodynamic studies were performed on separate occasions may be a limitation of the present study, however. Although the effort was made to make the conditions of examination equal as much as possible, there could be a minor variation in F 0 or sound pressure level, leading to relatively low corre- lations between HSDI parameters and acoustic/aerodynamic parameters. Another limitation may be the use of a rigid endoscope for the HSDI recording, which could yield unde- sirable laryngeal tension during the study. The short time in- terval for HSDI analysis as well as the relatively limited subject number (especially of male vocally healthy subjects) may be other limitations. Furthermore, the heterogeneity in the VFA group in the present study may have existed, although the selection of recruited subjects and the diagnosis was based on the agreement of three or four certified otorhi- nolaryngologists specializing in vocal treatment: Because the differential diagnosis among VFA, sulcus vocalis, and vocal fold scar is not always clear-cut, there is inevitable room for subjectivity. In the future study, the improvement of the study design by an introduction of simultaneous recording system of HSDI and acoustic signal or aerodynamic data, the introduction of trans- nasal flexible HSDI, the further refinement of analysis tech- nique with more automation that allows much extended time interval for analysis, and the expansion of subject number will be warranted. CONCLUSION The quantitative HSDI analysis of VFA revealed larger open quotients, lateral phase difference and integral glottal width (the average glottal width over a glottal cycle), and smaller speed index than vocally healthy subjects. Gender difference was noted in lateral phase difference, integral glottal width, and speed index. Correlation study revealed mild-to- moderate correlations between HSDI-derived parameters and conventional acoustic or aerodynamic parameters, and moderate-to-strong correlation among HSDI parameters. The combination of multiple HSDI analysis methods was effective in the objective documentation of vocal fold vibra- tions in VFA.

Phase difference With relatively larger N G

-lateral phase difference, vocal fold vi- brations in patients with VFA were more asymmetrical than those of vocally healthy subjects. Left-right difference of mass, tension, mucoelasticity of the vocal fold resulting from a different degree of muscular atrophy, and muscular/mucosal degeneration as well as asymmetry of the laryngeal frame may play a role here. 1,18,19 GAW parameters The GAW parameters failed to reveal significant intergroup dif- ferences although N L -minimal glottal area and N L -maximal glottal area were larger, and glottal area difference index was smaller in the VFA group as a trend. This result was consistent with the study of Bloch and Behrman 6 that reported no signif- icant difference in N L -minimal glottal area between the control and VFA groups. Larger N L -maximal glottal area found in the present study may be owing to an increased glottal flow in pa- tients with VFA ( Table 1 ), and decreased muscular tension of the vocal fold resulting from the muscular atrophy, leading to a greater lateral excursion of the vocal folds. 18 The smaller glottal area difference index observed in VFA signifies the decreased alternating current of glottal flow, the glottal flow ef- ficiency in other words. Glottal gap The result that 30% of elderly vocally healthy subjects had a glottal gap in the present study was consistent with the findings in the literature: Pontes et al 10 reported that the incidence of glottal gap in normal elderly population was 58%, for instance. Strictly speaking, the vocally healthy subjects with a glottal gap in the present study (as well as those in the study of Pontes et al, 10 perhaps) should be termed as ‘‘pathological but asymp- tomatic’’ rather than ‘‘normal,’’ though. Because the prepon- derant glottal gap was different between the control (anterior) and VFA groups (spindle shaped), the location of the glottal gap may serve as a clue to differentiate VFA from normal aging. Glottal outlet No significant intergroup difference of N L -glottal outlet in the present study was a contradictory result to the report by Bloch and Behrman, 6 who reported significantly smaller N L -glottal outlet in the VFA group than the normal group. One possible explanation is an interindividual difference of a maladaptive supraglottal hyperactivity as a compensatory strategy for incomplete or decreased glottal closure. 6 Another possible explanation is the posterior displacement of the petiole of epiglottis associated with a descension of the larynx observed in a male low-pitch phonation, 17 or an elevated laryngeal posi- tion observed in high-pitch phonation. 22 Limitations Overall, the combination of multiple HSDI analysis methods adopted in the present study was effective in the objective docu- mentation of vocal fold vibrations in VFA. Applying the same technique to the evaluation of other laryngeal pathology (eg,

Acknowledgments This research was not funded by any organization or grant. There was no conflict of interest to be disclosed.

REFERENCES 1. Kendall K. Presbyphonia: a review . Curr Opin Otolaryngol Head Neck Surg . 2007;15:137–140. 2. Yamauchi A, Imagawa H, Sakakibara K-I, et al. Vocal fold atrophy in a Jap- anese tertiary medical institute: status quo of the most aged country . J Voice . 2014;28:231–236. 3. Takano S, Kimura M, Nito T, et al. Clinical analysis of presbylarynx-vocal fold atrophy in the elderly individuals . Auris Nasus Larynx . 2010;37: 461–467.

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