What dose of botulinum toxin should I receive?
There is no standard Botulinum toxin dose. The dose for each patient with SD has to be customized for the patient due to the severity of his or her SD, the patient's voice demands and response to Botulinum toxin. The most common doses range from 1.0 to 2.5 units placed in the right and left vocal fold muscles for the treatment of AdSD. The range for a unilateral injection for AdSD is typically from 2.5 to 10 units.
Should I be receiving unilateral or bilateral Botulinum toxin injections for my SD?
Once again, there is no standard rules for injecting Botulinum toxin regarding dose or number of locations. Most commonly, bilateral injections are done for adductor spasmodic dysphonia. This is based on the notion that the disorder is bilateral and symmetric. However, in certain patients a unilateral injection may be preferable to minimize side effects. For AbSD, it is typical to inject either one side only or one side with a large dose and the other side a small dose. The patient will then return approximately three weeks following this procedure for a repeat injection, depending upon the response to the first injection.
What happens if I do not get treatment?
Available treatments for both forms of SD are able only to alleviate symptoms. Opting not to be treated has no effect on the underlying central nervous system disorder. Patients should only continue with treatment if they feel it is of benefit to them.
What are the common complications?
Most complications of treatment are the result of either inaccuracy of injection or inappropriate dosing of botulinum toxin.If an injection is not well placed, the toxin may have no effect, or it may be reduced. This can be corrected by repeating the injection.
Difficulty swallowing is probably the most common side effect. Since the larynx lies next to the entrance of the esophagus, and since laryngeal muscles are small and located fairly deep within the neck, toxin may inadvertently reach the esophageal or pharyngeal muscles. Weakening of these muscles, when added to the weakening of the vocal folds that results from treatment, can result in altered or impaired swallowing. Some temporary change in swallowing is reported by up to 17% of patients treated. In the vast majority of cases, this is more of an inconvenience than a danger. However, it is possible to impair swallowing more severely, and even theoretically to cause a lung infection from food entering the trachea (windpipe). Because the effect of botulinum toxin is temporary, it is usually necessary only to exercise caution while eating or drinking until the situation returns to normal. This is usually a matter of days or weeks, although in very rare cases, the problem may persist for the entire three months that the toxin has effect. Difficulty with swallowing (especially liquids) following botulinum toxin injection is often most noticeable with the first injection and may decrease with subsequent injections.
Infection as a result of botulinum toxin injection performed in the office with normal attention to cleanliness and sterile technique has not been reported.
Minor bleeding and bruising at the injection site may occur, especially in those patients who take aspirin or blood thinners. Serious bleeding has not been reported.
There are side effects specific to each type of SD as a result of over-dosing the affected muscles. Because botulinum toxin has a very pronounced effect for the first several days, some minor unwanted effects are often seen following injection. In AdSD, these consist of a soft, breathy voice and difficulty when drinking liquids. Both of these occur because the treated vocal folds are not able to come together completely. In AbSD, there may be some breathing restriction because the treated vocal fold is not able to move aside fully. Administering too much toxin results in these effects becoming more pronounced and lasting longer. Obviously, great care is used in the treatment of AbSD so as to avoid breathing difficulties.
Side effects can be minimized and sometimes even eliminated by altering dose or injection pattern feedback. Information from the patient's experience with the previous injection is essential in making the necessary adjustments and each new injection should be preceded by a discussion between patient and physician about the effects of the previous one.
What about surgical treatments for SD?
Surgery for SD, like surgery for all dystonias, is a second-choice treatment, used in those cases in which botulinum toxin treatment is, for one reason or another, not possible, ineffective or poorly tolerated. This is because in the past, a disappointingly large number of patients have had a recurrence of symptoms months to years after surgery. In this respect as well, surgery for SD is like surgery for other dystonias.
The idea behind surgery for SD is the same as the one behind botulinum toxin treatment: the weakening of muscles that spasm. Surgeons initially cut or crushed the nerve to the vocal fold, called the recurrent laryngeal nerve. Despite encouraging initial results, about two-thirds of patients developed symptoms of SD again within three years. Furthermore, one vocal fold remained paralyzed by this procedure, a condition that has its own drawbacks (link to Vocal Fold Paralysis). Surgeons have also tried cutting the secondary nerve to the larynx, known as the superior laryngeal nerve; thinning the muscle of the vocal fold (myectomy); and manipulating the larynx so that the vocal folds lie farther apart (lateralization thyroplasty) or are under less tension (anterior commissure release). None of these techniques has resulted in satisfactory long-term control of symptoms.