Spasmodic dysphonia, also known as laryngeal dystonia, is a rare neurological disorder characterized by involuntary muscle spasms of the larynx (voice box). Spasmodic dysphonia causes the voice to break, or to have a tight, strained or strangled quality. Patients with spasmodic dysphonia may have difficulty communicating clearly. The disorder appears most often in people between 30 and 50 years of age, and more frequently in women. It is a chronic lifetime condition whose cause is unknown.
Types of Spasmodic Dysphonia
There are two types of spasmodic dysphonia.
Abductor Spasmodic Dysphonia (AbSD)
In abductor spasmodic dysphonia, spasms cause the vocal folds to move apart (abduct) at the wrong time during speech, causing air leaks. The vocal cords cannot vibrate and produce sounds if they are too far apart. As a result, the voice frequently sounds breathy and weak. Spasms do not occur during laughing, shouting or crying.
Adductor Spasmodic Dysphonia (AdSD)
In the more common adductor spasmodic dysphonia, spasms in the vocal folds force them to come together (adduct) tightly at the wrong time during speech, making it difficult to produce sound. As a result, words are cut off and speech is choppy. Stress often exacerbates the condition. As with AbSD, spasms are not present during laughing, shouting or crying.
It is possible to have "mixed spasmodic dysphonia," a combination of AbSD and AdSD, which affects the muscles that both open and close the vocal folds. Cases of mixed spasmodic dysphonia are extremely rare.
Diagnosis of Spasmodic Dysphonia
The diagnosis of spasmodic dysphonia can be difficult because patients frequently have symptoms similar to those of other voice disorders. The diagnosis of spasmodic dysphonia is typically made by a team that includes an otolaryngologist (ear, nose and throat specialist); a speech-language pathologist; and a neurologist, who evaluates the patient for signs of other neurological disorders.
Treatment of Spasmodic Dysphonia
There is no cure for spasmodic dysphonia, so treatment options are designed to reduce or alleviate symptoms.
The most common spasmodic dysphonia treatment, which weakens or blocks nerve impulses to the muscle, is BOTOX® injection. BOTOX treatment is typically effective for 3 to 4 months, with continued injections necessary in order to keep symptoms at bay.
Voice therapy is another treatment option for mild cases of spasmodic dysphonia. In more severe cases, augmentative handheld devices can help to amplify speech. Assistive software can also be added to a computer or cell phone to translate text into synthetic speech.
When conventional treatment methods have failed, laryngeal surgery may be an option. Type I thyroplasty treats AbSD by implanting a shim that brings the vocal cords closer together to minimize the effect of spasms; type II thyroplasty uses a shim to keep the vocal cords from coming into contact with each other during spasms. Some patients have good results from thyroplasty, while others see little improvement.
Another surgical treatment is Selective Laryngeal Adductor Denervation-Reinnervation (SLAD/R), in which affected branches of laryngeal nerves are severed, and then reconnected to healthy nerves that are not involved in the dysphonia. According to the Dystonia Medical Research Foundation, studies indicate that the majority of patients are happy with the results of SLAD/R.