Muscle Tension Dysphonia (Muscular Tension Dysphonia)
In my opinion, muscle tension dysphonia (MTD) is a loose term that describes hoarseness resulting from inappropriate muscle contractions of the voicebox and/or neck while talking. Another key feature of MTD is that on examination, the voicebox anatomy is essentially normal, but functionally pathologic. Such a voicebox examination is performed by endoscopy. There are several different forms of muscle tension dysphonia which need to be clarified.
Compensatory MTD is when the body inappropriately contracts the muscles in and around the voicebox in a vain attempt to increase vocal volume or attain normal vocal quality to compensate for some type of hypofunction. Such hypofunction may be due to glottal incompetence or insufficient breath support. The resulting appearance of such compensatory behavior is the supraglottic squeeze where the sides and/or front and back of the larynx squeezes together (see pics below). Video example.
The video depicts a woman with severe lung disease with very poor vocal volume. Her body attempts to increase the vocal volume inappropriately by squeezing the voicebox ever tighter but inevitably fails. The key concept here is that the lungs power the voice. An analogy would be blowing a whistle very forcefully to create a loud noise versus blowing the whistle very gently which would result in a very soft noise. In fact, blowing a whistle is a good test to see what kind of volume one can attain with the voice. If you can't blow the whistle very loudly, one cannot obtain a strong voice.
Compensatory MTD is corrected by treating the underlying hypofunction.
Supraglottic MTD is also known as non-organic hyperfunction or non-organic dysphonia. Just as in compensatory MTD, there is a supraglottic squeeze present. In fact, when comparing photos depicting compensatory and supraglottic MTD, they may be indistinguishable. The first and fourth photos depict supraglottic MTD. The second and third photos depict compensatory MTD. The pictures below depict the varying appearances of supraglottic/compensatory MTD. The first picture/video is predominantly an anterior-posterior squeeze such that the back part of the voicebox is almost touching the front (AP squeeze). The second picture/video is predominantly a lateral squeeze such that the false vocal cords are touching and completely obscuring the true vocal cords (lateral squeeze). Most patients have varying combinations of both types. Click on the picture to view the video. Click here to see normal appearance.
The key concept here is that supraglottic MTD is a learned behavior. Most often, this type of MTD occurs after a viral upper respiratory infection (cold, flu, laryngitis, etc). In the initial setting of infection, the vocal cords become edematous and the person's voice becomes hoarse. In more rare situations, the viral infection may even temporarily induce a weakness or paralysis of the vocal cord. In either situation, some individuals continue to talk and constantly adjust their hoarse voice to try to attain a normal sounding voice. Such a strategy, which may initially improve their hoarse voice, ultimately backfires as once the infection resolves and the vocal cords return to normal, the person inappropriately continues to talk as if their vocal cords were still swollen/weakened.
Another cause for supraglottic MTD is stress. When an individual is under a lot of stress and having difficulty coping, the entire body starts to tighten up, but especially the muscles in the neck and at times, even the muscles of the voicebox. Such muscular tension may be so severe that the voice may even completely disappear. More commonly, swallowing may become affected with many individuals complaining of a lump in the throat (aka, globus pharyngeus).
In any case, this disorder is easily treated with voice therapy. Typically (though not always), people with supraglottic MTD have BETTER sounding voices at the upper range. As such, voice therapy begins where the voice sounds good (upper range) and the therapist attempts to help the patient carry the upper range good voice quality down into their normal voice range. It may take only one or two sessions to more than a dozen. Just like learning to sing, the patient MUST practice at home if they want their voice to recover as quickly as possible.
Before Voice Therapy
Voice Therapy Session
Performed by Dr. James Thomas
After Voice Therapy
In a nutshell, glottic MTD results in a gap between the vocal cords posteriorly (posterior glottic gap) during phonation due to inappropriate activation of the muscles that pulls the vocal cords apart (posterior cricoarytenoid muscles). In other words, as the body tries to bring the vocal cords together to phonate, other muscles inappropriately tries to pull them apart. The result is a somewhat breathy voice. I don't have a good example of this, but there is an excellent video discussing glottic MTD on a different website. In this video, the narrator defines the terms differently than I, but the concepts are still the same.
Now I added this disorder to this article since it is often erroneously confused with muscle tension dysphonia. They are two totally different entities and each are treated very differently from the other. Spasmodic dysphonia are involuntary spasms of the muscles causing sudden breaks in the voice while talking. Such breaks may be strangled/strained or breathy (audio/video examples). These spasms are no different than the involuntary eyelid twitches of blepharospasm. Just like blepharospasm, spasmodic dysphonia is treated with BOTOX injections. More information on this disorder can be found here.
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