ABductor spasmodic dysphonia involves spasms of the muscles that open the vocal folds — the opposite of the more common adductor form. During phonation, the PCA muscle fires involuntarily, pulling the cords apart and producing breathy breaks, most noticeably on voiceless consonants. It is rarer, more technically demanding to inject, and often requires more than one treatment to achieve the right dose.
The Injection
There are two common methods for injecting the muscles causing abductor SD. The original and most widely used method is for the physician to grasp the voicebox (the thyroid cartilage) and rotate it toward one side. A long needle is then passed in from the side of the neck until it reaches the back side of the voice box. When the muscle is identified by an EMG (electromyographic) signal, the Botox medication is instilled. The procedure is repeated from the opposite side.
The method Dr. Thomas uses — taught to him by Bob Bastian (Meleca, et al) — is translaryngeal, meaning through the voice box. It is similar to the adductor approach. Numbing medication is placed in the skin over the front of the voice box and then squirted into the voice box, causing a brief cough (and a bitter taste) before numbing the lining of the larynx.
After it is numb, a needle is passed through the front of the voice box and out the back. As the needle passes through the cartilage at the back of the voice box, it should be in the PCA muscle. The EMG confirms correct placement, and you may be asked to sniff — this activates the PCA and creates more activity on the EMG. If the needle goes too far, it may enter the esophagus, which would not activate with a sniff.
Most typically, both PCA muscles are injected. When these muscles are weakened, they can no longer open the vocal folds widely, which leads to noisy breathing — particularly on inhalation. Usually the dose is low enough that the PCA muscles still work partially, but with exertion there will be some shortness of breath. If you notice this, breathing more slowly is helpful: slower airflow through the narrowed airway creates less of the Bernoulli effect that draws the weakened cords together.
What to Expect After the Injection
The Initial Wait
For a day or two after the injection your voice will usually be unchanged. Approximately 24–72 hours from the injection the spasms begin to diminish and the voice may be stronger and steadier. At the same time you may — but not necessarily — start to experience shortness of breath. The breathing symptoms may not happen at all; they may be subtle; or they could be very noticeable and even uncomfortable and anxiety-provoking.
The Better Voice but Short of Breath Phase
This phase may last from a few days up to many weeks. Some patients experience no shortness of breath at all. During this phase you will notice that your voice is better, even though some spasms may remain. You may also experience some involuntary vocal sounds when you breathe in suddenly.
The “Talking Is Golden” Phase
For one to three months after the initial side-effect phase has passed, the voice often seems virtually normal. Talking is a pleasure, and some almost forget they even have spasmodic dysphonia during this time.
The Spasms Are Increasing Phase
Typically, during the second to fourth month after your injection you may find that your voice is again worsening. When you notice this happening, you may not need to return immediately for another injection — you may still have several to many weeks of reasonable vocal function. As spasms become more noticeable, arrange another injection appointment.
The Unsatisfying Response
Achieving a good result for abductor SD can be more difficult than for adductor SD. It usually requires more than one injection to arrive at the correct dose. Generally everyone involved is hesitant to give too large a dose because of the discomfort of the side effects and because there is no good treatment for the side effects — only waiting for them to resolve on their own.
The PCA Muscle
The main muscle that causes abductor SD is the PCA (Posterior Cricoarytenoid Muscle), located on the back of the voice box. It is the muscle that opens the vocal folds widely for breathing and is at its most active during sniffing. It should be basically at rest during speaking. If it contracts during phonation, the vocal cords open and a burst of air escapes — that is an abductor spasm.
This article by James P. Thomas MD is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.