Spasmodic dysphonia (SD) is a neurological voice disorder characterized by spasms in the vocal cords, which result in halting, jerky, hoarse, tight or gravelly speech. SD is believed to be caused by inappropriate signals sent from the brain’s basal ganglia, which is the area of the brain that governs voluntary motor control.

One manuscript published by the National Institutes of Health describes the use of diffusion tensor imaging (DTI) that may indicate abnormalities of the structure of the brain in patients diagnosed with SD. However, pinpointing the abnormalities remains out of reach.

Origins of SD

Spasmodic dysphonia, also called laryngeal dystonia, is one of a group of neurological disorders called dystonias. SD is referred to as a focal dystonia, because it affects (or focuses on) a single muscle or small group of muscles. The origins of SD are unclear, although researchers believe that there is a genetic link (as there is with generalized dystonias), it has not yet been identified. However, 12 percent of patients diagnosed with SD have reported relatives with similar voice problems or other dystonias.

Types of SD

There are two main types of spasmodic dysphonia:

» Adductor dysphonia (AdSD) — The more common type of SD, adductor dysphonia, is characterized by spasms that force the vocal cords closed, cutting off parts of speech, resulting in a strangled, strained voice. The speech may be uninterrupted, but sound strained or as if a lot of effort is made to speak.

» Abductor dysphonia (AbSD) — This form of SD is more rare, affecting about 1 in 9 people diagnosed with SD. The spasms involved in abductor dysphonia force the vocal cords open, resulting in a whispery voice, sometimes punctuated by near-normal speech.

The severity of symptoms varies with both types of SD; some cases present very mild symptoms that are barely noticed, with others more severe, causing pronounced speech problems. Some patients have both types of SD, called mixed dysphonia.

Although believed to be a rare disorder, affecting 50,000 to 100,000 people in the United States, recent research indicates that it is more likely that the disorder is frequently undiagnosed or misdiagnosed. Spasmodic dysphonia often develops in people ages 30 to 50, although younger people in their 20s and older people in their 90s can develop the disorder. Four times more women than men are diagnosed with SD.

Symptoms of SD

The onset of SD symptoms is usually gradual, exhibiting these qualities:

» Intermittent breaks in the voice while speaking that sound strangled, tremulous, hoarse, strained, jerky or nasal.

» Straining of voice, with excessive contractions of the vocal cords while speaking.

» Failure to maintain the voice while speaking, with increased effort to produce words beyond a whisper.

The muscle spasms of SD occur only while speaking. Spasms do not occur during exercise or normal breathing. Many patients report a lessening or absence of symptoms while singing or speaking in a high-pitched voice. Symptoms may periodically improve at random intervals and may worsen when tired or under stress.

Diagnosis of SD

There is no set diagnostic procedure for SD. If the condition is suspected, a number of tests conducted by specialists including ear, nose and throat specialists, neurologists and speech pathologists may be required to eliminate other voice disorders. A nasolaryngoscopy exam confirms the diagnosis. Click here to read more.

Treatment Options for SD

There is no cure for SD. Treatment often requires a multipronged approach. Coping skills, such as relaxation and stress reduction exercises, go a long way toward reducing symptoms. Voice therapy is also helpful in training the patient to speak in a manner that does not induce symptoms. In addition, injections of Botulinum toxin (Botox) into the muscles on both sides of the larynx have been proven to be effective in about 90 percent of patients with AdSD, while it is less effective for those with AbSD. Botox injections are a temporary treatment, requiring administration every three to six months.

The cost of Botox injections varies around the country. Administration is measured in units, with the cost ranging between $10 and $15 per unit. For patients undergoing treatment for SD, it may take 30t o 50 units or more to complete one treatment.

In severe cases, surgery to cut one or more of the muscles or nerves of the vocal folds may be required. This treatment may need to be repeated several months or years later, as symptoms often return.

— Lisa Moore is a senior writer for