The three types of spasmodic dysphonia (SD) are adductor spasmodic dysphonia, abductor spasmodic dysphonia and mixed spasmodic dysphonia.
Adductor spasmodic dysphonia
In adductor spasmodic dysphonia (ADSD), sudden involuntary muscle movements or spasms cause the vocal folds (or vocal cords) to slam together and stiffen.These spasms make it difficult for the vocal folds to vibrate and produce voice. Words are often cut off or difficult to start because of the muscle spasms. Therefore, speech may be choppy but differs from stuttering. The voice of an individual with adductor spasmodic dysphonia is commonly described as strained or strangled and full of effort. Surprisingly, the spasms are usually absent while laughing, speaking at a high pitch, or speaking while singing, but singers can experience a loss of range or the inability to produce certain notes of a scale or with projection. Stress, however, often makes the muscle spasms more severe.
Abductor spasmodic dysphonia
In abductor spasmodic dysphonia, sudden involuntary muscle movements or spasms cause the vocal folds to open. The vocal folds cannot vibrate when they are open. The open position of the vocal folds also allows air to escape from the lungs during speech. As a result, the voices of these individuals often sound weak, quiet and breathy or whispery. As with adductor spasmodic dysphonia, the spasms are often absent during activities such as laughing or singing, but singers can experience a loss of range or the inability to produce certain notes of a scale or with projection.
Mixed spasmodic dysphonia
Mixed spasmodic dysphonia involves both muscles that open the vocal folds and those that close them and therefore has features of both adductor and abductor spasmodic dysphonia