Maybe you have heard someone whose voice sounds tight, strangled, broken, whispery, or otherwise “not quite right.” It may be your own voice or that of someone you know. You may be trying to determine what is wrong, or a doctor may have already diagnosed the condition as spasmodic dysphonia (SD).
Spasmodic dysphonia belongs to a family of neurological disorders called dystonias. A dystonia is a movement disorder that causes muscles to contract and spasm involuntarily. Dystonias can be generalized, affecting the entire body, or focal, affecting only a specific area of the body or group of muscles. Following Parkinson’s disease and essential tremor, dystonia is the third most common movement disorder. The most common focal dystonia, cervical dystonia, causes the neck to twist or contort. Other dystonias can cause abnormal, involuntary blinking or spasm of the eyelids (blepharospasm), inappropriate contractions of the hand muscles (writer’s cramp), or uncontrolled movements from spasms in any of the muscles of the face, jaw, or tongue (oromandibular dystonia).
Certain dystonias, including SD, are task-specific, meaning that the muscles spasm only when they are used for particular actions and not when they are at rest. When a person with SD attempts to speak, involuntary spasms in the tiny muscles of the larynx cause the voice to break up, or sound strained, tight, strangled, breathy, or whispery. The spasms often interrupt the sound, squeezing the voice to nothing in the middle of a sentence, or dropping it to a whisper. However, during other activities, such as breathing and swallowing, the larynx functions normally.
Spasmodic dysphonia is estimated to affect approximately 50,000 people in North America, but this number may be somewhat inaccurate due to ongoing misdiagnosis or undiagnosed cases of the disorder. Although it can start at any time during life, SD seems to begin more often when people are middle-aged. The disorder affects women more often than men. Onset is usually gradual with no obvious explanation. Symptoms usually occur in the absence of any structural abnormality of the larynx, such as nodules, polyps, carcinogens, or inflammation. People have described their symptoms as worsening over an approximate 18-month period and then remaining stable in severity from that point onward. Some people have reported brief periods of remission, however this is very rare and the symptoms usually return.