Spasmodic Dysphonia Treatment Approach

The following is the fourth article in a series to address applications of Botulinum neurotoxin. We briefly presented the topic of Spasmodic Dysphonia in our post “Orofacial Applications Of Botulinum Neurotoxin”.  We will be delving into Spasmodic Dysphonia, in more detail, within this post.

Spasmodic Dysphonia, also known as Laryngeal Dystonia, is a neurological condition that affects a person’s speech.  This disorder is a focal dystonia and is due to the situation where the laryngeal muscles that are responsible for generating the voice, go into a period of spasm (1,2).

This results in breaks or interruptions in the voice, often occurring in every few sentences, which can create a situation where the afflicted become difficult to understand.  Onset is often gradual, and the condition that develops is lifelong.  The cause is unknown. 

Symptoms are less likely to occur at rest, while whispering, or on speech sounds that do not require phonation (9).  The thought it that this occurs because of an increase in sporadic, sudden, and prolonged tension found in the muscles around the larynx during phonation. This tension affects the abduction and adduction (opening and closing) of the vocal folds

Inability to retain subglottal air pressure required for phonation, and breaks in phonation, can be heard throughout the speech of people with spasmodic dysphonia (9).

Risk Factors include (10):

Being femaleInjury to the Larynx
Being middle aged (onset ~ 30-50 Years)Overuse of the voice
Family history of neurological diseasesCervical dystonia
Psychological stressChildhood measles or mumps
Upper respiratory tract infectionsPregnancy and delivery
Sinus and throat illnesses

The underlying mechanism is believed to involve the central nervous system.  Spasmodic Dysphonia is a type of Focal Dystonia, which affects approximately 2/100K people (1). 

Diagnosis may require a healthcare team, including:

NeurologistOtolaryngologist (ENT)
Physical Medicine and Rehabilitation (PM&R)Speech-language pathologist

There is no cure, however treatment may improve symptoms. 

There are three accepted types of Spasmodic Dysphonia: 

  • Adductor spasmodic dysphonia (most common)
  • Abductor spasmodic dysphonia
  • Mixed spasmodic dysphonia
Vocal Cord Anatomy graphic

Adductor Spasmodic Dysphonia

Adductor spasmodic dysphonia (ADSD) affects around 87% of individuals with SD and is the most common type (12).   ADSD is characterized by sudden involuntary muscle movements or spasms causing the vocal folds to squeeze together and stiffen (13).

ADSD is characterized by spasms that occur in the adductor muscles of the vocal folds, specifically the thyroarytenoid and the lateral cricoarytenoid (14).  These spasms make it difficult for the vocal folds to vibrate and produce voice. Words are often cut off or are difficult to start because of the muscle spasms.

Abductor spasmodic dysphonia

Abductor spasmodic dysphonia (ABSD) is the second most common type, affecting around 13% of individuals with SD (12) In ABSD, sudden involuntary muscle movements or spasms cause the vocal folds to open (12).

Here, 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.

Mixed spasmodic dysphonia

Mixed spasmodic dysphonia is the rarest 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 (12).  

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.

Treatment modalities include:

Injection of BoNT into the larynxCounselling
Voice therapyAmplification devices

The most common treatment involves injecting BoNT into the affected muscles of the larynx. 

This treatment approach generally last up to 3 months. There has been some evidence supporting better and longer lasting results when BoNT injections are paired with counselling (5,6,7,8).

The American Academy of Otolaryngology- Head and Neck Surgery, endorses the injection of Botulinum Toxin (BoTN) into the laryngeal muscles, as the primary treatment modality (5).

Botulinum toxin works by partially blocking the transmission of signals from the nerves to the muscles of the voice box.  This action helps to reduce the spasticity of these muscles by making them weaker, thereby smoothing speech.

This animated video illustrates the procedure, and in no way does this intend to be instructions as to how to carry out any procedure, as it is for illustration purposes only.

Myoguide™ EMG/ESTIM BoNT injection guidance system is designed to amplify EMG signals from muscle and provide audio and visual feedback to assist clinicians in locating areas of muscle activity.

Myoguide’s unique features support the clinician’s ability by providing a method to confirm the injection needle tip is inside the muscle before injecting the medication.

There are several advantages using The Myoguide Injection Guidance System when treating Spasmodic Dysphonia:

  • Myoguide bandwidth coverage ensures you will gain the widest spectrum of EMG signal and EMG audio feedback.
  • Myoguide has an AUDIO MUTE function, that will allow you to avoid startling your patient when the needle path moves from tissue to air, on the way to the vocal cords.  It is not uncommon to reach unstable amplifier states when the hypodermic needle electrode is disconnected from the patient (e.g. in air space).   This is one of the very unique conditions with this particular procedure.
  • Myoguide’s visual signal display allows viewing the EMG feedback, without the need for EMG audio.


  1. “Spasmodic Dysphonia”. NIDCD. 6 March 2017. Retrieved 16 June 2022.
  2. “Laryngeal Dystonia”. NORD (National Organization for Rare Disorders). 2017. Retrieved 16 June 2022.
  3. Murry, T (2014). “Spasmodic dysphonia: let’s look at that again”. Journal of Voice. 28 (6): 694–9. doi:10.1016/j.jvoice.2014.03.007. PMID 24972536.
  4. Albert, Martin L.; Knoefel, Janice E. (1994). Clinical Neurology of Aging. Oxford University Press. p. 512. ISBN 9780195071672.
  5. Antoine Eskander1, Kevin Fung, Simon McBride, Norman Hogikyan Current practices in the management of adductor spasmodic dysphonia.  J Otolaryngol Head Neck Surg. 2010 Oct;39(5):622-30.  PMID: 20828529
  6. 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
  7. 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
  8. 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
  9. Colton, R. H., & Casper, J. K. (2006). Understanding voice problems: A physiological perspective for diagnosis and treatment. Baltimore, MD: Lippincott Williams & Wilkins.
  10. Murry T (November 2014). “Spasmodic dysphonia: let’s look at that again”. Journal of Voice. 28 (6): 694–9. doi:10.1016/ j.jvoice. 2014.03.007. PMID 24972536.
  11. Childs L, Rickert S, Murry T, Blitzer A, Sulica L. Patient perceptions of factors leading to spasmodic dysphonia: A combined clinical experience of 350 patients. Laryngoscope. 2011 Jul 20.
  12. Kaye R, Blitzer A (November 2017). “Chemodenervation of the Larynx”. Toxins. 9 (11): 356. doi:10.3390/toxins9110356. PMC 5705971. PMID 29099066.’
  13. Definition of Spasmodic dysphonia”. MedTerms medical dictionary. Archived from the original on 2007-09-27. Retrieved 2007-05-11.
  14. van Esch BF, Wegner I, Stegeman I, Grolman W (2017). “Effect of Botulinum Toxin and Surgery among Spasmodic Dysphonia Patients”. Otolaryngology–Head and Neck Surgery. 156 (2): 238 254. doi:10.1177/0194599816675320. PMID 27803079. S2CID 4332852