Cause of spasmodic dysphonia is unknown. Patients often describe the onset of symptoms following an upper respiratory infection, a period of excessive voice use, or occupational or emotional stress. As a localized form of movement disorder, spasmodic dysphonia has an onset between ages 30 and 50 years, and about 60% of patients are women.
There are two forms:
In adductor spasmodic dysphonia, patients attempt to speak through the spasmodic closure of the vocal cords with a voice that sounds squeezed, effortful, or strained. These spasmodic episodes usually occur when vowel sounds are being formed, particularly at the beginning of words.
In abductor spasmodic dysphonia, which is less common, sudden interruptions of sound caused by momentary abduction of the vocal cords are accompanied by an audible escape of air during connected speech.
(See also Overview of Laryngeal Disorders.)
For adductor spasmodic dysphonia, surgery has been more successful than other approaches. Injection of botulinum toxin into vocal adductors has restored a normal voice in 70% of patients for up to 3 months. Because the effect is temporary, injections may be repeated.
For abductor spasmodic dysphonia, no known treatment permanently alleviates the disorder, but temporary improvement has been achieved with botulinum toxin delivered to the posterior cricoarytenoid muscle (sole vocal abductor, 1, 2). Surgical medialization (shifting toward the midline by inserting an adjustable spacer laterally) of both vocal cords appears to be promising (3).
Mor N, Simonyan K, Blitzer A: Central voice production and pathophysiology of spasmodic dysphonia. Laryngoscope 128(1):177-183, 2018. doi:10.1002/lary.26655
Dharia I, Bielamowicz S: Unilateral versus bilateral botulinum toxin injections in adductor spasmodic dysphonia in a large cohort [published online ahead of print, 2019 Dec 14]. Laryngoscope 10.1002/lary.28457, 2019. doi:10.1002/lary.28457
Dewan K, Berke GS: Bilateral vocal fold medialization: a treatment for abductor spasmodic dysphonia. J Voice 33(1):45-48, 2019. doi:10.1016/j.jvoice.2017.09.027