BOTOX® Injection for Laryngeal Spasmodic Dysphonia

Introduction

Spasmodic dysphonia (SD) is considered a type of focal dystonia, namely, laryngeal dystonia. The exact cause of this dystonia is currently unknown, but is believed to involve a region deep in the brain called the basal ganglia. This area of your brain is sending incorrect messages to the muscles controlling the movement of your vocal cords, causing them to contract inappropriately. (A description of the anatomy and function of the larynx is given elsewhere.) Briefly. if you have adductor-type SD, the muscles close your vocal cords too tightly and if you have the abductor-type the muscles open your vocal cords when they should be closed. Some individuals have mixed SD, or characteristics of both adductor- and abductor-type. Botulinum toxin (BOTOX® ) might minimize the symptoms of SD when injected into muscles involved with your disorder. This handout will provide you with some information about how BOTOX® works, the general technique of the botulinum toxin injections, as well as some of the possible complications.

[click picture to enlarge]
The image to the left shows a cross section of the vocal cords, viewed from above. For the most common type of SD, the thyroarytenoid muscle contracts too strongly, resulting in a strained voice. This is the muscle that is injected with BOTOX® .
The arytenoid is a small cartilage attached to the rear of the vocal cord. It rests on another piece of cartilage called the cricoid.
When breathing or speaking, the air passes through the region between the cords.

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General Information

The effect of the botulinum toxin is to weaken the involved muscles. Although the 'problem area' for dystonia appears to be at the base of the brain, we are only able to treat the disorder by injecting the involved muscle. Therefore it is important to remember that BOTOX® does not treat the cause of dystonia, but only provides temporary symptomatic relief. When the muscle is weakened, even though it is receiving abnormal signals from the brain, it cannot respond a strongly as before. This weakness provides the relief patients experience with BOTOX® treatments.

During the BOTOX® injection, you will lie down on an examination table with your head extended back over a pillow. It is helpful if you wear a shirt or blouse that has an open neck. For adductor-type SD, a local anesthetic is injected first so that the sensitive areas near the vocal cords is not stimulated when the BOTOX® needle is placed. The BOTOX® is injected through a very small needle which is connected by a wire to an electromyography (EMG) machine that records the activity of the muscle. The placement of the needle into the dystonic muscle is verified by the electrical signals shown on the EMG machine. At that point, through the same needle, the medication is injected. There generally is minimal discomfort associated with the injection.

[click picture to enlarge]
This image shows a side view of the manner in which the BOTOX® is injected. After numbing the area with a local anesthetic, the needle is passed under the thyroid cartilage into the muscles of the vocal cord. The entire procedure takes just a couple of minutes.

[click picture to enlarge]
The image to the left shows example of EMG recordings of the larynx. The recordings shown here are from three muscles; the left and right thyroarytenoid muscle, and one of the two posterior cricoarytenoid muscles. For the more common adductor spasmodic dysphonia, the injection is done into the thyroarytenoid muscle.

You should not eat or drink anything for 45-60 minutes after the injection. The anesthetic you received has numbed your throat and may cause you to cough if you try to swallow. Some patients may cough up some blood-tinged sputum during the first 24 hours after the injection. A small amount of bleeding, no more than a drop or two, occurs when the needle is inserted into the muscle, and this is what can appear in the sputum. Your neck may be slightly sore for a day or two from having the needles inserted, but this usually passes without any intervention needed.

You may begin to notice the effects of BOTOX® around 12-24 hours after the injection. It's effect is almost always noted by 48-72 hours and the full effect is established usually by one week, but sometimes as late as two weeks. Once the full effect is achieved, it slowly begins to wear off, although it is not noticeable in most cases for six to ten weeks.

BOTOX® prevents the release of the neurotransmitter at the connection between the nerve and the muscle, causing weakness of the muscle. Over time, the connection between the nerve and the muscle grows back, and therefore, the effect of BOTOX® is temporary. It generally lasts from 6 weeks up to 6-7 months. In most, the time between BOTOX® injections is about three to four months.

Since each muscle in each individual is different, the first one to three injections are calculated by estimating the severity of the dystonia Sometimes too little is given and relief is minimal. Sometimes, if an individual patient is very reactive to the botulinum toxin, an exaggerated response leading to significant weakness can be seen. Our hope is that after one or two sessions, the right dose for each individual can be found. There appears to be some variation even with identical injections so that in some eases, a greater effect or a lesser effect is experienced when compared to the previous identical injection.

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Possible Complications from BOTOX® Injection

There are two general complications associated with BOTOX® injections:

Antibody formation is noted only with higher, frequent doses of BOTOX® administration and is not generally found in patients who are receiving the medication for laryngeal dystonia.
The second effect, an exaggerated response to the medication, varies in terms of its effect by which set of muscles is injected:

Adductor spasmodic dysphonia: In this more common type, the muscles that bring the vocal cords together are the ones that are injected. If there is an exaggerated response to BOTOX® the vocal cords will not be able to get together during speech and swallowing. This results in a breathy voice or even in an inability to generate any voice at all. In addition, if the vocal cords do not get together during swallowing, some patients will experience choking when swallowing liquids. If swallowing problems occur, they are usually with handling liquids more than solids. In a few cases, although it is rare, some patients have required tube feedings. This was only temporary, until the effect of the BOTOX® wears off and swallowing function returns to normal. If you have difficulty swallowing after a BOTOX® injection, you should telephone us (Ms. Pat Waugh, 543-3134, Dr. Al Hillel, 548-4022) so that we can be sure that you are getting a safe, adequate diet.

Abductor spasmodic dysphonia: For this type of SD, the muscles that are injected are the muscles that move the vocal cords apart In the event of an exaggerated response, the vocal cords would not be able to move apart, therefore causing you to have difficulty breathing. It this occurs it is essential that you telephone us immediately (206/548-6190 - ask them to page otolaryngology resident) so that we can advise you of the proper action to take. Due to the significance of the effect we usually do not inject both muscles at the same visit with the same amount of medication. It is also essential that before each injection that the patient has a laryngeal examination to be sure that the muscles that move the vocal cords apart are working well.

The above information provides a general description about the effect of treatment with botulinum toxin. Although severe complications are not common, it is important that you know what they are so that you can be an active participant in your treatment. The more informed you are, the better you will be able to respond should a problem occur. It is important that you read the above information carefully and write down any questions for us that you might have regarding BOTOX® treatment.

DISCLAIMER:
It is always best to contact your own Otolaryngologist for questions you may have regarding health care. Each individual's situation is different and generalized answers are difficult to give in any aspect of medicine. The material given here may be helpful in providing additional information about common questions in Otolaryngology.