Otolaryngology head and neck surgery: an integrative view of the larynx

Looking for an Objective Parameter to Identify Early Vocal Dysfunctions in Healthy Perceived Singers

The finding of minimal laryngeal dysfunctions in professional voice users is essential to prevent the onset of organic vocal pathologies. The purpose of this study is to identify an objective parameter that supports the phoniatric evaluation in detecting minimal laryngeal dysfunctions in singers. 54 professional and non-professional singers have been evaluated with laryngostroboscopy, Multi-Dimensional Voice Program (MDVP), Dysphonia Severity Index (DSI), maximum phonation time (TMF), minimum intensity of sound emission (I-min), maximum frequency (F-max), voice handicap index (VHI), singing voice handicap index (SVHI), manual phonogram and audiometric examination. The SVHI of all the "healthy" singers was on average 23.7 ± 22.5, while that of the "dysfunctional" 20.9 ± 18. No statistically significant difference was found between the SVHI scores of the total of healthy singers compared to the scores of the dysfunctional ones on the VSL (p = 0.6). The between-group comparison of the means of individual parameter values of DSI, TMF, F-max, Jitter, Shimmer, NHR, and SPI was not statistically significant (respectively p = 0.315, 0.2, 0.18, 0.09, 0.2, 0.08, 0.3). The only parameter analyzed that was statistically significant was the I-min (p < 0.05). SVHI is a valid instrument for the evaluation after a therapy but in our experience, it is not useful in distinguishing healthy from dysfunctional patients. The minimum intensity of sound emission measured with the sound level meter (I-low2) resulted a reliable parameter to identify minimal laryngeal dysfunctions and a useful tool in supporting the phoniatric diagnostic-therapeutic process in singers.

Aesthesiometer-Based Testing for Laryngopharyngeal Hyposensitivity

OBJECTIVES/HYPOTHESIS

To develop a method for threshold estimation of the laryngeal adductor reflex (LAR) response using Cheung-Bearelly monofilaments.

STUDY DESIGN

Cross-sectional.

METHODS

Twenty-two healthy adults (12 men, 10 women) were tested for LAR response outcome using 30 mm 5-0 and 4-0 nylon monofilaments. Tactile stimuli were delivered to the aryepiglottic (AE) fold and medial pyriform sinus (MPS). Dichotomous classifier features and performance (area under the curve (AUC)), the LAR response outcome agreement and disagreement matrix, and test-retest reliability were examined. From those data, a test protocol that would minimize patient burden to estimate the LAR triggering threshold was formulated.

RESULTS

Classifier performance of 5-0 monofilament stimulation of the AE fold (sensitivity = 0.63, specificity = 0.63, PPV = 0.74, NPV = 0.25) and MPS (sensitivity = 0.45, specificity = 0.77, PPV = 0.74, NPV = 0.23,) was slightly below that of 4-0 monofilament stimulation of the AE fold (sensitivity = 0.82, specificity = 0.50, PPV = 0.82, NPV = 0.50) and MPS (sensitivity = 0.84, specificity = 0.64, PPV = 0.90, NPV = 0.56), based on AUC. LAR response outcome agreement for 5-0 and 4-0 stimulations was high (93%) for 5-0 positive response, but low (29%) for 5-0 negative response. Aesthesiometer test-retest reliability for LAR response outcome was excellent (Cronbach's alpha = 0.97).

CONCLUSIONS

Threshold estimation of the LAR response may be operationalized by adopting a decision tree protocol. For negative LAR response to initial 5-0 monofilament stimulation and positive response to subsequent 4-0 monofilament stimulation, the higher threshold is confirmed. Positive LAR response to 5-0 or 4-0 monofilament stimulation is expected in over 90% of asymptomatic adults. Negative LAR response to 4-0 monofilament stimulation identifies patients at risk for laryngopharyngeal hyposensitivity.

LEVEL OF EVIDENCE

3b Laryngoscope, 2021.

Laryngeal Adductor Reflex Movement Latency Following Tactile Stimulation

OBJECTIVE

To measure the latency of laryngeal adductor reflex (LAR) motion onset at 2 laryngopharyngeal subsites using calibrated aesthesiometers.

STUDY DESIGN

Cross-sectional.

SETTING

Academic institution.

METHODS

Twenty-one asymptomatic, healthy subjects (11 male, 10 female) underwent laryngopharyngeal sensory testing with tactile stimuli delivered to the aryepiglottic fold and medial pyriform sinus using 30-mm Cheung-Bearelly monofilaments (4-0 and 5-0 nylon sutures) via channeled flexible laryngoscope. The LAR onset latency, defined as the first visual detection of ipsilateral vocal fold adduction following tactile stimulation, was measured with frame-by-frame analysis of video recordings.

RESULTS

The overall mean LAR latency across both subsites and stimulation forces was 176.6 (95% CI, 170.3-183.0) ms, without significant difference between subsites or forces. The critical value for LAR response latency prolongation at the .01 significance level was 244 ms. At 30 frames/s video capture resolution, LAR response latency ≥8 frame intervals would indicate abnormal prolongation.

CONCLUSION

Aesthesiometer-triggered LAR latency appears to be invariant over an 8.7-dB force range and between the aryepiglottic fold and medial pyriform sinus subsites in controls. Laryngeal adductor reflex latency incongruences between stimulation forces or laryngopharyngeal subsites may serve as pathophysiological features to dissect mechanisms of upper aerodigestive tract disorders.

LEVEL OF EVIDENCE

Level 3B.

Optogenetic control of contractile function in skeletal muscle

Optogenetic stimulation allows activation of cells with high spatial and temporal precision. Here we show direct optogenetic stimulation of skeletal muscle from transgenic mice expressing the light-sensitive channel Channelrhodopsin-2 (ChR2). Largest tetanic contractions are observed with 5-ms light pulses at 30 Hz, resulting in 84% of the maximal force induced by electrical stimulation. We demonstrate the utility of this approach by selectively stimulating with a light guide individual intralaryngeal muscles in explanted larynges from ChR2-transgenic mice, which enables selective opening and closing of the vocal cords. Furthermore, systemic injection of adeno-associated virus into wild-type mice provides sufficient ChR2 expression for optogenetic opening of the vocal cords. Thus, direct optogenetic stimulation of skeletal muscle generates large force and provides the distinct advantage of localized and cell-type-specific activation. This technology could be useful for therapeutic purposes, such as restoring the mobility of the vocal cords in patients suffering from laryngeal paralysis.

Quantifying contributions of the cricopharyngeus to upper esophageal sphincter pressure changes by means of intramuscular electromyography and high-resolution manometry

OBJECTIVES

We sought to determine whether the association between cricopharyngeus muscle activity and upper esophageal sphincter pressure may change in a task-dependent fashion. We hypothesized that more automated tasks related to swallow or airway protection would yield a stronger association than would more volitional tasks related to tidal breathing or voice production.

METHODS

Six healthy adult subjects underwent simultaneous intramuscular electromyography of the cricopharyngeus muscle and high-resolution manometry of the upper esophageal sphincter. Correlation coefficients were calculated to characterize the association between the time-linked series.

RESULTS

Cricopharyngeus muscle activity was most strongly associated with upper esophageal sphincter pressure during swallow and effortful exhalation tasks (r = 0.77 and 0.79, respectively; P < .01). The association was also less variable during swallow and effortful exhalation.

CONCLUSIONS

These findings suggest a greater coupling for the more automatic tasks, and may suggest less coupling and more flexibility for the more volitional, voice-related tasks. These findings support the important role of central patterning for respiratory- and swallow-related tasks.