This page was written in response to an article from the Pittsburgh Post-Gazette, “The Hoarse Whisperer,” and has since been expanded to address issues relevant to informed consent. Dosing botulinum toxin for spasmodic dysphonia is a bit of an art — and one that is perhaps not well explained by some physicians. The major complaint of losing one’s voice is a side effect of the dosing, not the disorder itself. Commonly, patients receive too large a dose.
Variable Effects
Botulinum toxin has a variable effect on different people but is usually consistent in a given individual. This makes getting the proper dose a trial-and-error procedure at the beginning, since the amount needed by any one person may vary by a factor of 20 or more. The best dosage does not seem to be related to sex, age, weight, or any of the other usual measures physicians use.
Side Effects: The Core Trade-off
Since the medication treats the symptoms of the disorder and not its cause (which remains unknown), the goal of treatment should be in the hands of the patient. The two opposing factors are side effects versus duration of benefit. A large dose gives a longer beneficial effect but more initial side effects. A smaller dose gives fewer side effects but shorter benefit.
More specifically, the maximum duration of benefit for the average person with adductor spasmodic dysphonia is about 18 weeks — roughly four months. Once the dose is large enough to reach this duration, a diminishing return is obtained by going larger. To get four months of benefit, a typical patient will suffer through about a week of hoarseness — a breathy voice, a high-pitched squeaky voice, a non-projecting voice, or trouble swallowing liquids. Decreasing the dose can eliminate these side effects, though at the price of more frequent injections. By the time the dose is low enough to eliminate all breathiness, benefit typically shortens to about three months, meaning four shots per year instead of three.
If the First Dose Is Too Large
You will likely have side effects: a laryngitis-type voice, a squeaky voice, a whispery voice, or hoarseness. These occur because the initial weakness of the vocal folds prevents them from closing well — the weaker the folds from the injection, the worse the voice. When the vocal folds fail to come together for speech, it requires a lot of air to talk; patients complain of running out of breath, exhaustion when talking, and general fatigue. If the folds do not close well, swallowing becomes a problem — liquids tend to leak into the windpipe and cause choking and coughing.
If the dosage is way too much, these vocal effects might last three to four weeks and the swallowing problems one to two weeks. These side effects can be managed by talking less and thickening liquids, or by tucking the chin to the chest when swallowing. Fortunately, Botox treatments are temporary and all side effects will resolve. The most important next step is to decrease subsequent doses.
If the First Dose Is Too Small
Side effects are not an issue here. You may note improvement in your voice within one to seven days, but the improvement will be short-lived — perhaps as little as a week or two. The difficult judgment is whether the dose was too low or whether it was a missed injection. If in doubt, a small increase with the next dose is appropriate. If more than one injection is unhelpful, another consideration is to make sure the diagnosis is correct.
Patients Who May Prefer a Large Dose
Patients make decisions based on many factors. Consider a patient who lives alone, talks little, and has to travel a long distance to get the medication. Her insurance coverage is not wonderful and she abhors needles. She chooses a dose large enough that she loses her voice for a month and has to avoid thin liquids for a week after the injection. She waits six months before returning for another treatment. This is the best scenario in her mind, given that she has this disorder. The price: a roller-coaster voice and two injections per year.
Patients Who May Prefer a Small Dose
Another patient sells financial investment advice. His job suffers when his voice is strained. When he no longer sounds confident about his advice, no one trusts him, and he loses income. He chooses a very low dose of botulinum toxin that gives him no hoarseness at all. He returns for another injection at the tiniest vocal struggle. Thus, he has almost no dips and peaks in terms of vocal performance. The price: perhaps four injections per year.
Technique Issues
Injection technique also affects the outcome. If injections have extremely variable results despite the same dosage each time, it is possibly a result of more or less medication actually reaching the intended muscles. A person who is hoarse for a month after one injection and then has a perfect result with no breathiness at the next likely received two different amounts in the muscle rather than the medication having a different effect each time.
Dr. Thomas’s Approach
Philosophy of the injecting physician has a role at the initial treatment. Some physicians treat the patient with a dose that is sure to have an effect, given that the patient has traveled far or paid a large amount. Many of these patients will have a marked amount of initial breathiness. Other physicians start with a lower-than-average dosage so the patient gets a sense of the benefit without the side effects, then increase the dose to give a longer beneficial effect.
For Dr. Thomas, an average dosage is about 2¼ units total, split into two parts — one for each vocal fold. He usually starts at a low dosage and increases. He recommends a starting dose of about 1.8 units total, with a range from ½ unit total up to 20 units total. Following patient requests with appropriate precautions is the priority. Patients seem most satisfied with this approach.
What If I Decide Not to Have Treatment?
At this time, we do not know the cause of spasmodic dysphonia and so we do not have a cure. Botox treatments are directed at relieving symptoms. The condition tends not to be progressive and many patients have tolerated its difficulties for many years. As far as we know, nothing should happen if you decide not to treat with Botox. Those who do undergo treatment tend to have return spasms after several months, but they are usually not as severe as they were initially — so there seems to be some small prolonged benefit from the injections.
Cost of Treatment
The treatment is relatively expensive, and costs vary markedly across the United States and other countries. There are typically three or four costs associated with the injection: the physician’s injection charge, the EMG machine charge, and the medication charge. A significant amount of one vial (100 units, wholesale approximately $400 at year 2001 prices) is usually split among multiple patients injected on the same day, since the medication loses potency after thawing. Medicare guidelines require that the insurer of the last patient injected on a given day cover the cost of any unused medication remaining in the vial — a longstanding frustration. Patients are encouraged to ask about pricing before their injection.
Regulatory Status
The US Food and Drug Administration has not approved Botox specifically for laryngeal dystonia. However, once a drug is approved for any indication, physicians may apply their judgment and use it for other conditions at their reasonable discretion. Botox has been used successfully by many physicians for many dystonias beyond blepharospasm (its only FDA-approved indication). When Medicare began covering charges for Botox use in spasmodic dysphonia, most insurance companies followed. Patients should confirm their coverage before proceeding with an injection.
This article by James P. Thomas MD is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.