spasmodic dysphonia. For example, voiced sounds are more affected in adductor spasmodic dysphonia, while unvoiced sounds are more affected in abductor spasmodic dysphonia. 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. The movements that are found in this disorder are typically rhythmic in nature, as opposed to the muscle spasms of spasmodic dysphonia. It is important to note that voice tremor and spasmodic dysphonia can co-occur in some patients. Differential diagnosis is particularly important for determining appropriate interventions, as the type and cause of the disorder determine the most effective treatment. Differences in treatment effectiveness are present even between the types of spasmodic dysphonia. Diagnosis of spasmodic dysphonia is often delayed due to these challenges, which in turn presents difficulties in choosing the proper interventions. Types The three types of spasmodic dysphonia (SD) are adductor spasmodic dysphonia, abductor spasmodic dysphonia, and mixed spasmodic dysphonia. A fourth type called whispering dysphonia has also been proposed. Adductor spasmodic dysphonia is the most common type. Adductor spasmodic