Monday, November 10, 2014

Common Movement Disorders Affecting the Larynx: A Report from the Neurolaryngology Committee of the AAO-HNS

Albert L. Merati, MD, Yolanda D. Heman-Ackah, MD, Mona Abaza, MD, Kenneth W. Altman, MD, PhD, Lucian Sulica, MD, and Steven Belamowicz, MD. “Common Movement Disorders Affecting the Larynx: A Report from the Neurolaryngology Committee of the AAO-HNS.” Otolaryngology-Head and Neck Surgery (2005) 133, pp.654-665.

This article was written with the intention of detailing the necessity of a medical practitioner to become familiar with some impairments of the voice, brought on by various neurological disorders. While it is not a comprehensive list, it does highlight four of the most common disorders, and the idiosyncrasies of each. These include:
-       Stroke
-       Parkinson’s Disease
-       Voice Tremor
-       Spasmodic dysphonia
Interestingly enough, vocal fold paralysis, which is probably the most common impairment, is not discussed.

Albert L. Merati et al begin by mentioning the physical examinations a medical practitioner should take to become familiar with the nuances of each disorder. This starts by requesting a detailed history, evaluation of the voice, a neurolaryngological evaluation, and stroboscopic evaluation of the vocal folds. A typical evaluation includes a patient reading a text like the Rainbow Passage. This is because the Rainbow Passage is a standard exercise used to test the fundamental frequency of the voice, as well as ones ability to articulate. It achieves all goals thanks to it comprising all phonemes in the English language.

Then, the practitioner performs a neurolaryngeal examination in order to assess the mobility of the vocal folds, thus, revealing, or eliminating movement disorders. This is generally performed by using a flexible laryngoscope. Once the authors completed the discussion of the examination component, they moved onto the four disorders, starting with the “Stroke and the Larynx.” Points are made about the effects a stroke has on the voice and swallowing muscles, with specific attention to the neuroanatomy of phonation, speech, and language.

When the section “Dysphonia in Parkinson’s Disease” begins, the authors focus on the degeneration of the brainstem nuclei, and the signs one can observe in someone with this disorder. Apparently, this is the most common movement disorder in patients over the age of 55. Then, like the other disorders, the section on the “Essential Voice Tremor” addresses how to distinguish it from other underlying tremors such as, asymptomatic tremor, Parkinsonian tremor, myoclonus and tics, or spasmodic dysphonia. As is generally understood, by eliminating possible disorders and getting to the root of the issue determines the kind of treatment (or management) the will patient receive. This review not only focuses on laryngeal disorders stemming from a neurological impairment, and the ways in which we can discern them apart, but also, the methods of either treating, or managing the disorder.

Merati et al conclude this review by pointing out that they have only touched on four neuromuscular disorders, and in order for it to be more complete, they would have had to cover myasthenia gravis (grave muscle weakness), amyotrophic lateral sclerosis, multiple sclerosis and more. You see, many disorders impact on the “phonatory, respiratory, and deglutitive function of the larynx.”[1]

As a musician, who is placing a possible career in the reliance of two muscles (as well as others) that are only around 20mm long, it is easy to be scared by the various disorders that could possibly affect ones larynx. To think that you might be at the height of your career, only to experience a stroke, or suffer from Parkinson’s Disease. In an instant, you would have to reevaluate your career and choose something else. Yes, it is scary for anybody, and not just singers, for no-one wishes to be affected by such neurological disorders, but there is something about the individual voice for a singer. I believe singers are more in touch with their vocal apparatus than non-singers – it is part of our core being. For this reason, as a singer, I am pleases to see that “neuromuscular impairment continues to be such a dominant topic in the study of laryngeal disorders.” (Albert L. Merati et al.)

What was interesting to observe in this review was that during a neurolaryngeal examination, practitioners are diagnosing movement disorders (neurologic integrity) of the larynx, and relating them to the possible site of the brain causing this sign.

Here is the table represented in the review:

 Table 2
Upper motor neuron and lower motor neuron signs in the larynx
Upper motor neuron
Spastic paresis of muscle groups
Decreased agility
         Basal ganglia
Resting tremor
Intention tremor
Lower motor neuron
         Peripheral neuropathy
Isolated flaccid paresis or paralysis
Decreased agility
Normal coordination
         Neuromuscular junction
Fluctuating abnormalities

But what was really interesting was to see how these disorders are treated (or not). The stroke patient is advised to work with a speech pathologist; the Lee Silverman Voice Treatment is recommended to patients with Parkinson’s Disease; the initial stage of treatment for essential tremor is drug administration, primarily of a ß-adrenergic blocker that reduces tremor amplitude (while it is not highly successful, it does bring relief in 50% of patients[2]); and BOTOX is pointed out as a treatment in a variety of dystonias. In 2005, BOTOX was the primary choice for patients.

In my last review, I discussed focal dysphonia and how BOTOX (botulinum toxin) injections were the norm because “traditional therapy is often not successful.” However, Merati et al discuss the possibility of surgical management. Procedures include: a recurrent laryngeal nerve section, a recurrent laryngeal nerve resection, a thyroarytenoid muscle myectomy, an expansion laryngoplasty, and most recently, a selective laryngeal adductor denervation-reinnervation operation. While 41% of patients experience a mild to severe tightness in the laryngeal function, 83% of postoperative voice patients felt that their voice improved. While this seems to have made a significant difference in the lives of many people, I personally would not be quick to jump on board. Voice therapy with a speech pathologist, and perhaps BOTOX injections would be as far as I go. But surgery, no thank you! For someone who depends on their voice, I would choose anything that doesn’t have the opportunity to do further damage.

At this moment in the reading however, I started to remember our class with Dr. Sylvain Moreno (Research Scientist at the Baycrest Research Institute), where he discussed Brain Plasticity and its ability to adapt itself. It was mentioned that after a patient suffers from a stroke, through repetitive training, and creating stronger pathways between neurons each time, the brain can redevelop its skills. Sadly, not all treatments of a neurological disorder [affecting the larynx] have such positive results, but it is pleasing to note that neuroscience is advancing. And this is an assuring possibility that demonstrates a possible positive treatment outcome. But can this concept of brain plasticity relate to not just stroke patients, but to other patients suffering from neurolaryngeal disorders? How fantastic would it be if we did not need to resort to drugs, BOTOX and surgery?

I would be interested to see if newer research/reviews have been made on this topic, and if nearly 10 years since this review was printed, we have better options. I assume there would be, but I’ll save that for my next bit of research!

Works cited:
Albert L. Merati, MD, Yolanda D. Heman-Ackah, MD, Mona Abaza, MD, Kenneth W. Altman, MD, PhD, Lucian Sulica, MD, and Steven Belamowicz, MD. “Common Movement Disorders Affecting the Larynx: A Report from the Neurolaryngology Committee of the AAO-HNS.” Otolaryngology-Head and Neck Surgery (2005) 133, pp.654-665.

Koller WC, Hristova A, Brin M. Pharmacologic treatment of essential tremor. Neurology 2000: 54, S30-38

[1] Common Movement Disorders Affecting the Larynx: A Report from the Neurolaryngology Committee of the AAO-HNS p.664
[2] Koller WC, Hristova A, Brin M. Pharmacologic treatment of essential tremor. Neurology 2000: 54, S30-38

1 comment:

Eventide said...

I understand your concern as a singer when reading about the various disorders of the voice, and the need for noninvasive treatment options. You reference Sylvain Moreno’s lecture, and yes, the singing voice is much more resistant to the effects of stroke than the speaking voice. Because speech centers are so localized in the left hemisphere, a left hemispheric stroke can result in aphasia, but the client can still sing, and this becomes a vehicle for restoring language function. In professional singers like yourself, the arcuate fasciculus in the right hemisphere is much more developed than in the average population, and this links motor regions with the homologous speech language areas in the right hemisphere - MIT is used to develop this connection and promote speech using right hemispheric networks. So there’s a lot of potential in using the singing voice to restore speech/language function for certain types of left hemispheric strokes. I don’t know much about the other conditions - it would be interesting to find out - but one thing is certain, the less invasive the better, and if singing techniques work, then what better way!