What is Spasmodic Dysphonia?
Spasmodic Dysphonia is a type of dystonia, a class of disorders of central motor processing (the part of the brain that controls movement) that cause involuntary movements in the affected body part. Dystonias can affect the entire body (generalized dystonia) or just one part (focal or segmental dystonia). Spasmodic Dysphonia is a dystonia that is limited to the larynx.
Examples of other dystonias include blepharospasm (involuntary eye blinking) and torticollis (wry neck). Among neurologists, Spasmodic Dysphonia is known as focal laryngeal dystonia. Spastic dysphonia is an older term that is synonymous with spasmodic dysphonia. There are two types: Adductor spasmodic dysphonia (AdSD), so named because it affects the muscles that bring together (adduct) the vocal folds during speech, is the more common of the two (85-90% of cases). Abductor spasmodic dysphonia (AbSD) affects the opposite muscle group, which moves apart (abducts) the vocal folds during speech. These involuntary movements cause the symptoms of Spasmodic Dysphonia, which are discussed below. The condition usually occurs by itself, and is very rarely associated with other, more serious neurologic diseases.
Spasmodic Dysphonia Causes
There do not appear to be any behaviors or environmental factors that increase the chance of contracting Spasmodic Dysphonia. Researchers believe that the disorder stems from abnormal brain cell activity in a part of the brain called the basal ganglia. The cause of this is unknown. Spasmodic Dysphonia, like all focal dystonias, is a disorder of unknown cause. Affected persons have reported the onset of symptoms following trauma to the head, common upper respiratory infections, routine intubation for general anesthesia and dental work. However, no clear relationship between any of these conditions and Spasmodic Dysphonia exists.
Symptoms of Spasmodic Dysphonia
Involuntary, abnormal motion of the vocal folds (spasms) causes the characteristic voice changes of Spasmodic Dysphonia. In AdSD, the vocal folds come together with too much force and at inappropriate times, producing strained, strangled breaks in connected speech. In AbSD, the vocal folds spread apart inappropriately during speech, causing breathy or soundless breaks. In both cases, voice breaks, or spasms in the voice occur irregularly. The voice will usually "break" or be interrupted on specific sounds and parts of the word. This occurs typically during voiceless to voiced transitions during speech (i.e. "T" and "P" sounds followed by a vowel). For example, when an AbSD patient says the sentence "Pay Paul a penny" there will usually be a breathy, voice break immediately after each "P".
The severity of the symptoms usually varies from day to day, and even over the course of a single day. It is possible for the voice to be normal sometimes, and affected at other times. It is clear that anxiety or fatigue causes symptoms to be more noticeable. Speaking to strangers, public speaking, or speaking in unaccustomed situations often makes symptoms worse, probably because all of these situations increase anxiety. Most people with Spasmodic Dysphonia report that using the telephone is especially difficult. Conversely, symptoms are usually mildest in familiar situations. Anything that functions as a sedative, including a glass of wine or beer, can improve symptoms.
Most people gradually become aware that their speech is requiring more conscious effort. Over weeks to months, the characteristic voice breaks become more noticeable and pronounced. The severity of the voice disturbance may vary considerably in the initial stage of the disorder. Over time, it becomes more consistent. There is no evidence that the disorder worsens over the course of a person's life, nor, unfortunately, is there evidence that it improves or resolves. Patients with Spasmodic Dysphonia almost never lose completely the ability to communicate.
Spasmodic Dysphonia Treatment
There is no cure for Spasmodic Dysphonia. Available treatment is intended only to improve symptoms, and happily, that is almost always possible. It is important to understand that treatment does not affect the course of the disorder. In other words, if a person elects not to be treated, the symptoms will not become worse.
Voice therapy, by itself, has not been useful in controlling the symptoms of Spasmodic Dysphonia. Voice therapy can help control side effects of treatment discussed below, and can help a person manage the anxiety that often make the symptoms worse. Voice therapy may be helpful following botulinum toxin treatment (see below) by helping the person to: (1) eliminate the body's poor compensation behaviors; (2) adjust to the changes in the voice from treatment and; (3) maximize the beneficial effects of the treatment.
Spasmodic Dysphonia is an organic disorder of the central nervous system. As a result, psychological/psychiatric treatment is not an effective primary treatment. However, any chronic condition can be emotionally and psychologically draining. Because Spasmodic Dysphonia affects the voice, it is especially so. A mental health professional may help affected people better handle the stresses associated with this disorder.
Many medications that act on the central nervous system may be beneficial in dystonia. Unfortunately, at doses that relieve symptoms, there are often significant side effects like sedation and memory loss. Direct treatment of the involved muscles has generally proven to be of greater benefit. In most cases of Spasmodic Dysphonia, oral medication is not used at all, or is used only as an auxiliary therapy.
Botulinum Toxin Treatment
Laryngeal injections of botulinum toxin are the main therapy for Spasmodic Dysphonia. Botulinum toxin is a naturally occurring substance that weakens muscle by blocking the release of acetylcholine from nerve endings. Acetylcholine is a substance that triggers muscle contraction. The effects of botulinum toxin are temporary, lasting about three months, and dose-dependent, so that the muscle weakness is proportional to the amount of toxin used. Research has found that there is a "plateau effect" at higher doses of botulinum toxin; however, at the typical low doses used for the treatment of Spasmodic Dysphonia, there is a consistent dose dependent response. Of the eight types of botulinum toxin that exist, two are available for use in humans - botulinum toxin type A (Botox®, Allergan Inc., Irvine, California, and Dysport®, Ipsen Ltd., United Kingdom) and botulinum toxin type B (Myobloc®, Elan Pharmaceuticals, Dublin, Ireland). Botox® is the formulation most often used in the United States.
Botulinum toxin has been used in humans since 1979, and in Spasmodic Dysphonia since 1984. In that time, it has been shown to be safe and effective in the treatment of Spasmodic Dysphonia, and is recognized as such by the American Academy of Otolaryngology - Head and Neck Surgery. Botulinum toxin is not approved by the United States Food and Drug Administration for use in Spasmodic Dysphonia, and none of the companies that produce it have plans to pursue such approval, probably because the relatively small amount used to treat this condition makes this process financially unrewarding. Because the use of botulinum toxin to treat Spasmodic Dysphonia is not FDA approved, the manufacturers are not permitted (in the U.S. ) to discuss information related to this use. Nevertheless, general information is available from each company (see below). The principle behind botulinum toxin treatment is to weaken the muscles that are hyperactive. In the case of AdSD, these are muscles that bring the vocal folds together, and in AbSD, muscles that bring the vocal folds apart. Botulinum toxin is usually injected through the skin of the neck into the appropriate spots with the aid of electromyography (EMG). (LEMG link) This is an office procedure. Afterwards, the patient may usually go on with the normal activities of the day. The discomfort associated with the injection commonly disappears after a day or two.
In AdSD, because the muscles that bring the vocal folds together are initially "over weakened," injection is normally followed by a period of breathy, whispery voice and sometimes coughing when drinking liquids. This may last for up to two weeks. Most otolaryngologists aim to adjust the botulinum toxin dose to limit the "breathy" period to one week. In AbSD, the situation is more complicated, as inadequate parting of the vocal folds might result in difficulty breathing. For this reason, AbSD injections are often staggered, with one vocal fold injected one or two weeks after the first. Sometimes, a treating physician may prefer to treat just one side per three-month "cycle" to minimize these effects. Often, the dose of botulinum toxin can be adjusted to minimize unwanted effects. In the case of AdSD, for instance, decreasing the dose can usually shorten the duration of the breathiness, but the overall length of benefit may be decreased. Obviously, each person prefers to be injected as infrequently as possible, but each has a different tolerance for the breathy voice period following the injection. People to whom voice is crucial, like lawyers or schoolteachers, may opt for smaller doses at more frequent intervals.