Monday, October 20, 2014

Sonographic detection of basal ganglia abnormalities in spasmodic dysphonia

U. Walter, A. Blitzer, R. Benecke, A. Grossmann and D. Dressler. “Sonographic detection of basal ganglia abnormalities in spasmodic dysphonia.” European Journal of Neurology 2014, 21: pp.349–352

A voice disorder characterized by involuntary contraction or spasms of the vocal cords causing interruptions of speech and affecting the voice quality, spasmodic dysphonia is an extremely focal form of dystonia. The exact cause of spasmodic dysphonia (SD) is unknown, but “research has revealed increasing evidence that most cases of spasmodic dysphonia are in fact neurogenic or have to do with the nervous system.” The authors of this study/communication, knowing that abnormalities of the lenticular nucleus are a finding in dystonia, wanted to study whether Transcranial Sonography detects basal ganglia abnormalities also.

Fourteen patients with spasmodic dysphonia were studied – 10 women, 4 men, who had experienced the disease for 16.5 +/- 6.1 years, as well as 14 healthy patients. Transcranial sonography of the basal ganglia, substantia nigra and ventricles was performed bilaterally through the pre-auricular acoustic bone windows. Where the sonography is of benefit is that it can image blood flow in the major intercranial arteries rapidly, and non-invasively. An increased echo response was reported in the lenticular nucleus (LN) in 12 spasmodic dysphonia patients but only one from the group of healthy patients, therefore revealing that there was a correlation between LN hyperechogenicity and adductor spasmodic dysphonia.

The authors discuss the idea that the extent of the correlation between the two – the severity of spasmodic dysphonia, “conforms to the idea that copper accumulation might directly influence symptom severity…copper accumulation in the LN could explain disinhibition of the thalamus via disturbed functions of neurons of the globus pallidus internus.” Studies have also shown that there is a reduction of the copper-transporting protein, Menkes, in the basal ganglia in dystonia patients.

Through digital analysis, the area of lesions revealed a link with spasmodic dysphonia severity, allowing the researchers the chance to link the underlying pathology of spasmodic dysphonia to that of more widespread forms of dystonia. The larger the echo response on an ultrasound had a direct relation to the severity of the dysphonia.

Last year, the first year Master of Voice Performance and Pedagogy students had the opportunity to be instructed by Aaron Low (Speech Pathologist) at The Voice Clinic in Toronto. For eight, two hour classes, we not only studied the anatomy and function of breathing, the larynx, vocal folds, pharynx, vowels and articulation, but we also looked at voice assessment techniques and the possible causes of voice problems. When it came to discussing the possible causes of voice problems, we referred to “The Voice: A Medical Guide for Achieving and Maintaining a Healthy Voice” by Yolanda D. Heman-Ackah, Robert T. Sataloff, and Mary J. Hawkshaw. In chapter 7, they talk about Spasmodic Dysphonia, what it is, and that the most common treatment is an injection of botulinum toxin, simply because “traditional voice therapy is often not successful.”

As someone who is intrigued with the singing voice and of teaching singing, I believe it falls upon the instructor to know not only of various speech ‘defects,’ but to learn of how to recognize it, and of the treatments available. The things to look for include: in the more common adductor type of spasmodic dysphonia, a tight, strained voice quality, often characterized by excessive closure of the vocal folds during speech (abrupt starting and stopping of the voice), whereas the abductor type causes a breathy, whispering voice, un-phonated bursts. However, this book doesn’t state how it is caused. It only mentions that it is a neurological disorder. It is for this reason that this Journal Article titled “sonographic detection of basal ganglia abnormalities in spasmodic dysphonia” was an interesting read.

If you observe the ultrasounds, as well as the graphs, one is able to see that the area of lesions revealed on digital analysis a link with spasmodic dysphonia severity. In this instance, for those patients whose grade of spasmodic severity was higher, echo response in the basal ganglia would also be larger. And on the other end of the scale, LN hyperechogenicity was a lot smaller for a patient whose severity of spasmodic dysphonia was less pronounced. This clearly shows that there are abnormalities of the basal ganglia in spasmodic dysphonia patients. Also, the authors suggest, “copper accumulation might directly influence symptom severity.” As we may be aware, the Menkes protein helps regulate the copper levels in the body. With a reduction of the Menkes protein in the basal ganglia, there is an increased level of copper, which modulates synaptic function and acts as an inhibitor of several receptor types.

It is fantastic that discoveries (or hypotheses) like these are being made. Medicine and science advances when people look for answers and it seems this group of neuroscientists have made a link between the severity of the dysphonia and an increased level of copper. When a cause is discovered, it seems possible to find a way to diminish the problem. In this instance, perhaps we should look for a way to diminish copper levels, for not only does it have an affect on Spasmodic Dysphonia, but also on Alzheimer’s Disease and Wilson’s Disease.

As someone who is interested in the human voice, and who comes from a pedagogical background, to explore spasmodic dysphonia further through this study was absolutely fascinating. It seems like there is more research out there, as well as research that needs to be done. I look forward to being provided with more answers on this topic in due course.

Works cited:

Yolanda D. Heman-Ackah, Robert T. Sataloff, and Mary J. Hawkshaw. “The Voice: A Medical Guide for Achieving and Maintaining a Healthy Voice” Narberth, PA: Science and Medicine Inc., 2013

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