ABductor spasmodic dysphonia involves the muscles that open the voice box for breathing. If they spasm while speaking the person develops an involuntary whisper while trying to speak. For more detail, listen to a sample of ABductor spasmodic dysphonia.

What to expect from a Botox injection for ABductor spasmodic dysphonia

The PCA muscle

The main muscle causing ABductor spasmodic dysphonia is the Posterior Cricoarytenoid Muscle (PCA), see photos below. It is located on the back of the voice box. It is the muscle that widely opens the vocal folds for breathing. It is at its most active during sniffing. It should be basically at rest during speaking. If it contracts during the making of a sound (phonation), then the vocal cords open and a breath of air comes out. That is an ABductor spasm. To hear a sample of a female voice with ABductor spasms, play the following.

Left: the relaxed right PCA muscle’s bulk between the left arrows is small. Right: the right PCA muscle has contracted, (pulling the vocal cords slightly apart) and the increased thickness of the right PCA muscle is visible between the right arrows.

Left: the relaxed right PCA muscle’s bulk between the left arrows is small. Right: the right PCA muscle has contracted, (pulling the vocal cords slightly apart) and the increased thickness of the right PCA muscle is visible between the right arrows.


Learn more about the anatomy of the voice box in this picture.

The injection

There are two common methods for injecting the muscles causing ABductor spasmodic dysphonia. The original and most widely used method is for the physician to grasp the voice box (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 that Dr. Thomas uses 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. This causes a brief cough (and a bitter taste from the medication) and then numbs the lining of the voice box, which is otherwise very sensitive. 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 is used to ascertain the needle placement in the muscle and you may be asked to sniff. This activates the muscle and causes more activity on the EMG. If the needle goes too far, it may still be in a muscle, but that muscle would be the swallowing tube (the esophagus). It would not activate with a sniff.

Typically, both sides (both PCA muscles) are injected. There are two exceptions. In some patients, only one side is spasming. However, the most common reason is fear on the part of the physican or patient. When the muscles opening the voice box widely are weakened, they cannot open widely. This leads to noisy breathing, most particularly when breathing in. Breathing out is fine, but normally the vocal folds move away from each other on breathing in and when they do not, they will vibrate. This creates a sound during breathing that can be frightful if one is unprepared. Usually, the dose of Botox is low enough that the PCA muscles still work a bit. However, with exercise, there will tend to be shortness of breath. This is the opposite of Botox injections for ADductor spasmodic dysphonia which cause a breathiness when there is a bit too much medication. Keep in mind that the slower you breathe, the less the vocal cords will pull together and the less noise you will make breathing. 

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 a shortness of breath. In other words, 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/short of breath" phase

This phase may last from a few days up to many weeks. Again, some do not experience any shortness of breath. During this phase, you will notice that your voice is better, even though some spasms remain. You may also experience some involuntary vocal sounds when you breathe in suddenly.

The "talking is golden" phase

For 1-3 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 increase" 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, because you may still have several to many weeks of reasonable vocal function. As spasms become more noticeable, you should arrange another injection appointment.

The unsatisfying response

Achieving a good result for ABductory spasmodic dysphonia can be more difficult than for ADductory spasmodic dysphonia. It usually requires more than one injection to get the correct dose. Generally everyone involved is hesitant to give too big 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.