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
Abductor spasmodic dysphonia (ABSD) is the second most common type, affecting around 13% of individuals with SD. In ABSD, sudden involuntary muscle movements or spasms cause the vocal folds to open. As the name suggests, these spasms occur in the single abductor muscle of the vocal folds, called the posterior cricoarytenoid. 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 is the most rare type. 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. Some researchers believe that a subset of cases classified as mixed spasmodic dysphonia may actually be ADSD or ABSD subtype with the addition of compensatory voice behaviours that make it appear mixed.
Following speech assessment, the otolaryngologist conducts a flexible transnasal laryngoscopy to view the vocal folds and activity of the muscles controlling them in order to eliminate other possible causes of the voice disorder. In spasmodic dysphonia, producing long vowels or speaking sentences results in muscle spasms which are not observed during other vocal activities such as coughing, breathing, or whispering. To evaluate the individual for any other neurological problems, this examination is followed up with an assessment by the neurologist. Voice quality symbol
The voice quality symbol for spasmodic dysphonia is ꟿ. Differential diagnosis
Because spasmodic dysphonia shares many characteristics with other voice disorders, misdiagnosis frequently occurs. A common misdiagnosis is muscle tension dysphonia, a functional voice disorder which results from use of the voice, rather than a structural abnormality. Some parameters can help guide the clinician towards a decision. In muscle tension dysphonia, the vocal folds are typically hyperadducted in constant way, not in a spasmodic way. Additionally, the voice difficulties found in spasmodic dysphonia can be task specific, as opposed to those found in muscle tension dysphonia. Being able to differentiate between muscle tension dysphonia and spasmodic dysphonia is important because muscle tension dysphonia typically responds well to behavioural voice treatment but spasmodic dysphonia does not. This is crucial to avoid providing inappropriate treatment, but in some cases a trial of behavioural voice treatment can also be helpful to establish a differential diagnosis.Spasmodic dysphonia can also be misdiagnosed as voice tremor.