A look into the Laryngeal Electromyography world! Re: Influence of Superior Laryngeal Nerve Injury on Glottal Function

Summary

In a study by Dr. Armando De Virgilio from the September 2014 issue of “Otolaryngology - Head and Neck Surgery”[1], he enters the world of laryngeal electromyography (LEMG) in order to evaluate certain laryngeal functions to help enhance standard neurolaryngeal methodologies. He explains that Recurrent laryngeal nerve (RLN) injuries may induce unilateral vocal fold paralysis (UVFP). During thyroidectomy, the most common cause of UVFP, the superior laryngeal nerve (SLN), is also at risk of injury. In the literature, the influence of SLN injury on glottal configuration and function in patients with UVFP remains controversial. His study investigates SLN injury influence on glottal configuration and function in patients with UVFP after thyroidectomy.

The SLN and RLN function of 34 patients with UVFP after thyroidectomy was determined by laryngeal electromyography. The subjects were dichotomized into the isolated RLN injury group (n = 26) or the concurrent SLN/RLN injury group (n = 8). He evaluated glottal angle and paralyzed vocal fold shape during inspiration, normalized glottal gap area, and glottal shape during phonation. The glottal function measurements included voice acoustic and aerodynamic analyses and the Voice Handicap Index. The aforementioned parameters of the RLN and concurrent SLN/RLN injury groups were compared.

There were no statistical differences in glottal configuration such as glottal angle, paralyzed vocal fold shape, normalized glottal gap area, and glottal shape between the RLN and concurrent SLN/RLN injury groups. He explained that there were also no significant differences in other glottal function analyses including fundamental frequency, mean airflow rate, phonation quotient, maximal phonation time, and Voice Handicap Index. In the present study, Dr. De Virgilio did not find any evidence that SLN injury could significantly influence the glottal configuration and function in patients with UVFP.

Reflection

This study by Dr. Armando De Virgilio is fascinating and discovers underlying topics in glottal configuration aside from unilateral vocal fold paralysis patients. These results can help singers and speakers discover a thing or two. As the field of Neurolaryngology evolves, I find that literature is starting to understand the neurological role of intrinsic laryngeal muscles, which help us understand the overall function. In this study, laryngeal electromyography (LEMG) is used to report the integrity of the neuromuscular system in the larynx by recording action potentials generated in the laryngeal muscles during voluntary and involuntary contraction. LEMG is particularly useful for helping to differentiate between disorders involving upper motor neurons, lower motor neurons, peripheral nerves, the neuromuscular junction, muscle fibers, and the laryngeal cartilages and joints.

As I read this article, I cannot help but be happy that studies like Dr. De Virgilio exist so we can understand the exact mechanism of the problem and why it is important in helping the physician, speech language pathologist and singing teacher comprehend how to rehabilitate the voice by using neurological data. He strictly states that a study with a larger scale remains necessary to further clarify this specific topic. What about evaluating the breathing mechanism simultaneously with his LEMG data? What is lacking in Dr. De Virgilio’s study is muscle activity that can be recorded by an ambulatory monitoring system with surface EMG using silver/silver chloride bipolar electrodes. Laryngeal muscles (especially the phonatory/glottal process) cannot function without the breathing mechanism. This occurs when air is expelled from the lungs through the glottis, creating neurological connections to the brain and a pressure drop across the larynx. When this drop becomes sufficiently large, the vocal folds start to oscillate. If the breath is not sufficient, there will be a lacking result in neurological connectivity and pressure drop across the larynx.

If Dr. De Virgilio added breathing muscle activity to his study, would these results in unilateral vocal fold paralysis patients cause an alternative discussion and help enhance standard methodology for evaluating superior laryngeal nerve function? In 2005, Dr. De Viggo Pettersen did a SLN/RLN study[2] using LEMG but also connecting breathing muscles and thorax movement. It concluded that Sternocleidomastoideus and Scaleus muscle activity in classical singing is of greater functional significance in balancing the subglottal pressure than the role of Upper trapezius as a pressure generator during glottal configuration. Dr. De Virgilio may be lacking data from unilateral vocal fold paralysis patients without recorded data from these three breathing muscle groups.

Far more research is needed to fully understand the complex relations between posture, muscle usage and breathing in any patient, unilateral vocal fold paralysis or not. I appreciate how Dr. De Virgilio approached this study because I personally think he is enhancing standard methodologies in LEMG.

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[1] "Influence of Superior Laryngeal Nerve Injury on Glottal Configuration/Function of Thyroidectomy-Induced Unilateral Vocal Fold Paralysis." American Academy of Otolaryngology—Head and Neck Surgery September.2014 (2014). SAGE Publications. Web. <http://oto.sagepub.com/content/early/2014/09/11/0194599814549740.full.pdf>.

[2] Pettersen, Viggo. "From Muscles to Singing The Activity of Accessory Breathing Muscles and Thorax Movement in Classical Singing." University of Stavanger Department of Music and Dance. NTNU, 2005. Web. <http://www.diva-portal.org/smash/get/diva2:125600/FULLTEXT01.pdf>.

Sound-contingent visual motion aftereffect

Hidaka, S., Teramoto, W., Kobayashi, M., & Sugita, Y. (2011). Sound-contingent visual motion aftereffect. BMC Neuroscience,12, 44. doi:http://dx.doi.org/10.1186/1471-2202-12-44

Summary:

The authors analyze the new neural connections that can be created after a brief (3 min) exposure to simultaneous motion signals and sound frequencies. The main purpose of the study is to prove that the brain, regardless of age, can create interconnections between sound and movement when exposed to certain stimulus. They also prove how these interconnections are still present after 2 days of being exposed. This principle is based in the fact that visual movements are usually accompanied by some sound in real life. They emphasize in the concept of “contingent motion aftereffect” referring as an effect that is still present after a previous stimulus. More specifically, the authors refer to how the brain can easily associate information from combined sensory inputs. In their experiment they test how the brain can associate a series of dots moving in certain directions (left and right) with two different sound frequencies (2 kHz and 500 Hz).

In the first stage of the experiment the participants had to look at an area containing several dots moving in different directions every 500ms. The dots' movement coherence was alternated: 0%, 3.75%, 7.5% 15% or 30% moving leftwards or rightwards, while the rest of the dots were moving in random directions. The participants had to determine in which direction the majority of the dots were moving (left or right). During this phase, participants had an auditory stimulus of 500ms duration alternating randomly from 2 kHz or 500 Hz unrelated to dot movement. The second phase of the experiment consisted in exposing the participants to a similar experiment but with a 100% movement coherence (all points move either to the right or to the left). In this phase, high frequency 2 kHz is synchronized with leftward movement while low frequency is synchronized with rightward dot movement. The participants were exposed to these audio visual stimuli during 3 minutes. In the third stage of the test, participants were exposed to the same test as in the beginning (random movement, and no relation between tones and movement direction).

In order to determine the effects to the exposure, researchers elaborated a series of statistical tests to determine the failure of participants to determine the real direction of movement before and after the 3 min exposure. In this analysis they also included the results obtained when participants had no auditory stimulus. Surprisingly, results showed that the participant’s visual motion perception was heavily affected after the second phase of the test when they were exposed to direct correlation between movement and tones, meaning that their ability to identify the direction of movement was diminished. When they were hearing the 2 kHz tone they perceived it as a right movement regardless of real direction and vice versa with the low 500 Hz frequency. More importantly, this effect remained present after two days when the participants were tested again.

Reflection:

One important thing to notice is the short length of exposure vs. the effect duration.  So, if this kind of effect can be achieved under this short exposure to repeated sounds and images I wonder what would be the effect on doing this repetitively, once per day for example. Moreover, it will be interesting to see how this concept can be used in learning techniques or to improve some particular skills. I also found quite interesting how the authors discuss the validity of the results by comparing them with other studies that might suggest that the responses might be biased when the visual input is not completely clear. They reject the possibility of having a “biased decision” because of the participant uncertainty by doing additional focused vision tests. Nevertheless this particular experiment is based in the fact that there are no other visible objects in the periphery which is far from reality. I believe this kind of studies that explore the ability of the brain to create new neural representations relating sound and movement could be potentially useful for improving certain skills considering all the audio/visual media we are exposed every day.

Trauma-related dissociation as a factor affecting musicians’ memory for music: Some possible solutions

Summary:
Inette Swart, Caroline van Niekerk, Woltemade explores trauma-related dissociation, identified as a factor contribution to memory problems in this report and extensive study about the influence of trauma on musicians. They looked into musicians onstage, participants during practice and lessons, and temporary amnesia for music due to severe trauma (such as PTSD -- Post-Traumatic Stress Disorder).

The researchers investigated on and discussed the nature of memory function in the musician, optimal performance and focus, trauma and dissociation and the resultant ways in which it interferes with memory. The effects of trauma on the unconscious mind, nature of associations, its working memory, and also, the similarity of states of optimal concentration and pathological dissociation. These effects are discussed to potentially enhance understanding of how trauma can negatively affect musicians’ memory. Observations are made by extensive qualitative research survey, including students’ and teachers’ self-reports, and narratives of three musicians participating as case studies. In order to search for effective solutions, the researchers offered promising intervention strategies, such as Eye Movement Desensitization and Reprogramming, Eye Movement Integration, hypnosis, body therapies, and movement.

Reflection:
This article provides detailed information on trauma and how it affects the musicians’ music-making, focusing much on memory during music performance. What I found interesting was that, they did not focus much on the study and examples of the collection of data. The author stated that, “the study is also exploratory in nature,” (119)  making the assumption that the reader understands exactly, the procedure of this research.

The paper relies heavily on information based on other journals and researches. It compiles extensive literature and hence, providing the reader a vast amount of facts and possible solutions for trauma. In addition to short literature reviews of many researches, the authors also explore what dissociation and trauma is, while defining it and what happens. The authors explored in depth, of the possible therapeutic solutions, such as EMDR (Eye Movement Desensitization and Reprocessing) and EMI (Eye Movement Integration), hypnosis, body therapies and the role of movement (focusing on Dalcroze methods), with the emphasis on future directions of this research.

As mentioned, this research seems to be much more of a factual paper based on others’ researches rather than explaining the authors’ own research. It quickly explained the methodology but did not reveal results. I’m more interested to see their findings based on the results they received from the qualitative research (especially the results from the questionnaires), and the data they received from the three case studies (in which they did not cover in depth). Instead of a research paper focusing on their participants, it would be a much more successful paper that focused on others’ researches, and providing an analysis paper based on literature. Perhaps, using the participants may not have deemed necessary, or useful as information in another paper.

Works cited:
Swart, Inette., van Niekerk, Caroline and Hartman, Woltemade. “Trauma-related dissociation as a factor affecting musicians’ memory for music: Some possible solutions.” Australian Journal of Music Education (2010). Nedlands, Australia. 2:117-134.