People who have muscle disorders that cause excessive contraction or tightening of the muscles are said to have dystonia. When these kinds of contractions take place in the muscles that control the vocal cords, the patient may have a neurological disorder known as spasmodic dysphonia.
Spasmodic dysphonia, or SD, is a disorder of the central nervous system. There is no known cause for this disorder, although it is believed to be a type of dystonia, which originates in the portion of the brain that coordinates muscle movement. People of all ages, races, and ethnicities can have SD. Symptoms usually appear between age 30 and 50 and are more common in women than in men.
The anatomy of talking
During normal speech, air passes through the larynx or voice box in the throat. Inside the larynx, two vocal cords or folds lie opposite each other. The vocal folds are bands of smooth muscle that are attached to other muscles in the larynx. When we breathe, these folds open to allow the air to pass through. When we speak, the folds press against each other. The air passing between them causes them to vibrate, which produces the sounds of speech or singing.
What happens during spasmodic dysphonia
There are three types of spasmodic dysphonia:
• Adductor SD – In this type of SD, the muscles that control the vocal folds spasm and force the folds to slam together and stiffen. This makes it difficult for them to vibrate and produce sounds. People with this type of SD may have speech that is choppy and may sound similar to stuttering. The voice may sound strained, as though it takes great effort to speak. Stress can make these spasms worse. Symptoms may go away while whispering, laughing, singing, or speaking in a high pitch voice or speaking while breathing in.
• Abductor SD – In this type of SD, spasms in the muscles cause the vocal folds to open, which prevents them from vibrating. The open folds also allow air to escape during speech, so people with this type of SD may sound whispery, breathy, quiet, or weak.