Healthcare: Neurology

Spasmodic Dysphonia


What Is Spasmodic Dysphonia?


Spasmodic dysphonia is a neurological disorder caused by a dystonia (abnormal sustained muscle contraction) of the vocal cords. Depending on the vocal cord muscles that are affected, there are three types: adductor (involuntary vocal cord closing), abductor (involuntary vocal cord opening), or mixed. Adductor SD is more common and presents with a strained or strangled voice with irregular voice breaks. The severity of spasmodic dysphonia varies throughout the day and from day to day. Abductor dysphonia presents as excessive breathiness, pauses in the middle of the word, and difficulty in generating adequate volume of speech. Mixed dysphonia patients often have a chaotic combination of inappropriate adduction and abduction, resulting in halting speech and variable breathiness and tightness. Singing, shouting, and laughter may change the characteristics of all three types of dysphonia. In addition to their phonation difficulties, many patients with SD have an associated tremor of the voice, hands and head. This condition may be very debilitating especially for professionals such as teachers, trial attorneys or performers.

Little is currently known about the incidence and prevalence of SD. There may be between 10,000 to 30,000 affected individuals in the United States as reported by the National Spasmodic Dysphonia Association, although this may grossly underestimate the true prevalence. Spasmodic dysphonia, like most focal dystonias, tends to emerge gradually in young adulthood or midlife (peak time of onset age 30-50 years) and then reaches a plateau, when the severity of symptoms remains constant. The disorder predominantly affects women (2.5:1). Spontaneous remission occurs in a small percentage of patients, but it is usually transient and the symptoms may recur after a few weeks or months. Repetitive vocal cord strain and laryngeal trauma may precipitate SD.




The diagnosis of SD is challenging. Individuals suffering from this disorder are often initially misdiagnosed as psychogenic (so-called muscle tension dysphonia). An accurate diagnosis is critical as misdiagnosis delays the time to initiation of effective therapy. Most commonly, SD is diagnosed based on the clinical evaluation (see characteristics of the different types of SD above) combined with direct visualization of the vocal cords (videolaryngoscopy).




The cause of SD remains unknown, but the disorder is classified as a form of focal dystonia (syndrome of abnormal sustained muscle contractions) involving the vocal muscles. This neurologic disorder is probably caused by impairment in the normal motor control mechanisms within the basal ganglia (deep brain structures which help regulate movement). A few cases with single mutations in THAP1, a gene involved in transcription regulation, suggest that there may be a weak genetic predisposition. SD may occur isolated or as part of a segmental dystonia, when it is associated with involuntary spasms of the face, jaw and neck muscles (cranial or craniocervical dystonia). SD may also occur in patients with more generalized dystonia, also involving the trunk and limbs. This form of dystonia is often of genetic origin with several genes or gene markers already identified. (See related information on dystonia.)




Minor adductor overactivity may improve with speech therapy, relaxation techniques or alteration of vocal pitch. Oral medications (such as trihexyphenidyl or benzodiazepines) may be effective in mild cases, but botulinum toxin injections are clearly the treatment of choice for most patients. Techniques of injecting botulinum toxin into the vocal cords include percutaneously (through the skin) unilaterally or bilaterally, or through a transnasal fiberoptic approach. The effect may last up to three months and most patients are able to sustain a benefit with two to four injections per year. Voice therapy and voice rest following the injections of botulinum toxin may prolong the benefit of botulinum toxin. Treatment with botulinum toxin injections is proven to be effective in treating SD, and it has markedly changed the prognosis of the disease. Finally, surgical treatments, such as neuromodulation (direct electrical stimulation of the muscle) and muscle surgery, has been attempted with mixed results.


Selected References


Bielamowicz S, Squire S, Bidus K, Ludlow CL. Assessment of posterior cricoarytenoid botulinum toxin injections in patients with abductor spasmodic dysphonia. Ann Otol Rhinol Laryngol. 2001 May;110(5 Pt 1):406-12.

Brin MF, Blitzer A, Stewart C. Laryngeal dystonia (spasmodic dysphonia): observations of 901 patients and treatment with botulinum toxin. Adv Neurol. 1998;78:237-52.

Chang CY, Chabot P, Thomas JP. Relationship of botulinum dosage to duration of side effects and normal voice in adductor spasmodic dysphonia. Otolaryngol Head Neck Surg. 2007 Jun;136(6):894-9.

Chitkara A, Meyer T, Keidar A, Blitzer A. Singer's dystonia: first report of a variant of spasmodic dysphonia. Ann Otol Rhinol Laryngol. 2006 Feb;115(2):89-92.

Djarmati A, Schneider SA, Lohmann K, Winkler S, Pawlack H, Hagenah J, et al. Mutations in THAP1 (DYT6) and generalised dystonia with prominent spasmodic dysphonia: a genetic screening study. Lancet Neurol. 2009 May;8(5):447-52.

Fahn S, Jankovic J, Hallett M, eds. Principles and Practice of Movement Disorders, 2nd ed., Churchill Livingstone, Elsevier, Philadelphia, PA, 2011. (Accompanied by a DVD of movements disorders.)

Gündel H, Busch R, Ceballos-Baumann A, Seifert E. Psychiatric comorbidity in patients with spasmodic dysphonia: a controlled study. J Neurol Neurosurg Psychiatry. 2007 Dec;78(12):1398-400.

Jankovic J, Schwartz K, Donovan DT. Botulinum toxin treatment of cranial-cervical dystonia, spasmodic dysphonia, other focal dystonias and hemifacial spasm. J Neurol Neurosurg Psychiatry. 1990 Aug;53(8):633-9.

Ludlow CL. Spasmodic dysphonia: a laryngeal control disorder specific to speech. J Neurosci. 2011 Jan 19;31(3):793-7.

Murry T, Woodson GE. Combined-modality treatment of adductor spasmodic dysphonia with botulinum toxin and voice therapy. J Voice. 1995 Dec;9(4):460-5.

Nomoto M, Tokashiki R, Hiramatsu H, Konomi U, Motohashi R, Sakurai E, et al. The Comparison of Thyroarytenoid Muscle Myectomy and Type II Thyroplasty for Spasmodic Dysphonia. J Voice. 2015 Jul;29(4):501-6.

Pitman MJ. Treatment of spasmodic dysphonia with a neuromodulating electrical implant. Laryngoscope. 2014 Nov;124(11):2537-43.

Simpson DM, Blitzer A, Brashear A, Comella C, Dubinsky R, Hallett M, et al. Assessment: Botulinum neurotoxin for the treatment of movement disorders (an evidence-based review): report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology. 2008 May 6;70(19):1699-706.

Whurr R, Lorch M. Review of differential diagnosis and management of spasmodic dysphonia. Curr Opin Otolaryngol Head Neck Surg. 2016 Jun;24(3):203-7.

Wong DL, Adams SG, Irish JC, Durkin LC, Hunt EJ, Charlton MP. Effect of neuromuscular activity on the response to botulinum toxin injections in spasmodic dysphonia. J Otolaryngol. 1995 Aug;24(4):209-16.