Laryngeal dystonia (vocal fold spasms) is intermittent spasm of laryngeal muscles that causes an abnormal voice.
Laryngeal dystonia is an idiopathic dystonia that affects the muscles of the larynx during specific movements of the larynx. As a localized form of movement disorder, laryngeal dystonia has an average age of onset of 51 years, and approximately 80% of patients are women (1). A family history of neurological disorders (including dystonia and tremor), recent viral illness, and heavy voice-use have been implicated as risk factors.
Reference
1. Patel AB, Bansberg SF, Adler CH, Lott DG, Crujido L. The Mayo Clinic Arizona Spasmodic Dysphonia Experience: A Demographic Analysis of 718 Patients. Ann Otol Rhinol Laryngol. 2015;124(11):859-863. doi:10.1177/0003489415588557
Symptoms and Signs of Laryngeal Dystonia
There are 3 main forms of laryngeal dystonia:
Adductor laryngeal dystonia
Abductor laryngeal dystonia
Mixed laryngeal dystonia
In adductor laryngeal dystonia, a patient's voice sounds squeezed, effortful, or strained due to uncontrolled closure of the vocal folds during speech. These spasmodic episodes usually occur when vowel sounds are being formed, particularly at the beginning of words.
In abductor laryngeal dystonia, which is less common, sudden interruptions of sound caused by uncontrolled opening of the vocal folds are accompanied by an audible escape of air during connected speech.
Those with mixed laryngeal dystonia may display features of both adductor and abductor laryngeal dystonia to varying degrees and at different times.
Diagnosis of Laryngeal Dystonia
History and physical examination
The diagnosis is primarily clinical and involves a history of physical examination, including laryngoscopy to visualize and assess the vocal folds and their movement during phonation. Diagnostic confusion may arise when distinguishing between laryngeal dystonia and muscle tension dysphonia (1). The symptoms of laryngeal dystonia are associated with specific speech sounds, while muscle tension dysphonia does not have this correlation. Voice assessment by a speech-language pathologist may be helpful in guiding diagnosis as well as treatment.
Diagnosis reference
1. Hintze JM, Ludlow CL, Bansberg SF, Adler CH, Lott DG. Spasmodic Dysphonia: A Review. Part 2: Characterization of Pathophysiology. Otolaryngol Head Neck Surg. 2017;157(4):558-564. doi:10.1177/0194599817728465
Treatment of Laryngeal Dystonia
Botulinum toxin injection
Selective laryngeal nerve section and reinnervation surgery
For adductor laryngeal dystonia, injection of botulinum toxin (BoNT) into vocal adductors has become the standard of care. Targeted injections are generally safe and improve symptoms in the majority of patients for up to 12 weeks (1, 2). Because the effect of BoNT is temporary, injections must be repeated to maintain the improvement. Selective laryngeal nerve section with reinnervation surgery is also an option in certain centers. Laryngeal nerve section without reinnervation has been shown to result in synkinesis and is not the preferred approach to this condition.
For abductor laryngeal dystonia, 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) (3, 4).
Treatment references
1. Hyodo M, Nagao A, Asano K, et al. Botulinum toxin injection into the intrinsic laryngeal muscles to treat spasmodic dysphonia: A multicenter, placebo-controlled, randomized, double-blinded, parallel-group comparison/open-label clinical trial. Eur J Neurol. 2021;28(5):1548-1556. doi:10.1111/ene.14714
2. Stachler RJ, Francis DO, Schwartz SR, et al. Clinical Practice Guideline: Hoarseness (Dysphonia) (Update) [published correction appears in Otolaryngol Head Neck Surg. 2018 Aug;159(2):403. doi: 10.1177/0194599818766900.]. Otolaryngol Head Neck Surg. 2018;158(1_suppl):S1-S42. doi:10.1177/0194599817751030
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
4. 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
