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  • Updated 06.19.2024
  • Released 08.14.1995
  • Expires For CME 06.19.2027

Laryngeal dystonia

Introduction

Overview

A dystonia is characterized as involuntary muscle contractions. Dystonia can be divided into primary dystonia, in which there is no identified neurologic lesion, or a secondary dystonia, in which there is an identifiable lesion, such as lesions within the basal ganglia in Parkinson disease. Dystonia can also be focal, regional, or diffusely affect the entire body. Laryngeal dystonia, previously called spasmodic dysphonia, is a focal dystonia involving the intrinsic musculature of the larynx (thyroarytenoid, lateral cricoarytenoid, interarytenoid or posterior cricoarytenoid muscles). The more common type, adductor laryngeal dystonia, involves the muscles that adduct, or close, the vocal cords (thyroarytenoid, lateral cricoarytenoid, and interarytenoid muscles) and typically results in strained, strangled, effortful speech with breaks in phonation. Abductor laryngeal dystonia, which is less common, involves the paired posterior cricoarytenoid muscles, which are the only muscles that abduct, or open, the larynx for breathing. Abductor laryngeal dystonia generally causes breathy speech with voiceless pauses.

The task-specific nature of this condition means that the hyperfunctional muscular spasms occur with speech, but voice and function may be normal with other laryngeal activities, such as swallowing, coughing, laughter, yawning, and singing.

Laryngeal dystonia is typically diagnosed by history, listening to the voice, and laryngeal endoscopic videostroboscopy to exclude other disorders. Several causative genes have been identified for some forms of laryngeal dystonia, although it usually is idiopathic. As in other focal dystonia disorders, the mainstay of treatment for laryngeal dystonia is botulinum toxin injections into the affected musculature. Patients can experience side effects after botulinum toxin injections, although these are usually transient. Dosage of botulinum toxin is titrated to maximize improvement while minimizing side effects.

Key points

• The diagnosis of laryngeal dystonia is made clinically based on perceptual voice evaluation combined with laryngeal endoscopy.

• Adductor laryngeal dystonia typically results in strained, strangled, effortful speech with breaks in phonation.

• Abductor laryngeal dystonia generally causes breathy speech with voiceless pauses.

• Both adductor and abductor laryngeal dystonia are rare, with females more likely affected than males, although adductor laryngeal dystonia is more common than the abductor form.

• The disorder was initially considered psychogenic, but subsequent studies have confirmed the neurogenic origin.

• EMG-guided botulinum toxin injections into the intrinsic laryngeal musculature have become the mainstay of treatment for laryngeal dystonia.

Historical note and terminology

Laryngeal dystonia is a focal dystonia resulting in task-specific, action-induced spasm of the vocal cords. Historically, Tiberius Claudius Drusus Nero Germanicus, who became emperor of Rome 41 AD, has been suspected to have laryngeal dystonia (162). It was first described by Traube in 1871 as a “nervous hoarseness” in a young girl and assigned the label of spastic dysphonia (205). The patient only spoke with great effort, and “the laryngoscopic examination revealed spastic closure of the vocal cord, whereby the left arytenoid cartilage shifted in front of the right one while probably also the vocal cords were particularly overlapping of each other” (178). Schnitzler may be the first one to suspect organic etiology, in 1895, in two patients with “cramping of the vocal cord and forced voice” (181), who also had synkinesis of facial muscles and abnormal movements of the arms and legs (104). Schnitzler termed the condition “aphonia spastica” or spastic dysphonia. Due to the lack of other coexisting neurologic deficits, the disorder continued to be considered psychogenic (74; 178; 11). A century later, Aronson pointed out the wax and wane characteristic and proposed the term “spasmodic” instead of “spastic,” which implies rigidity (08; 09). Robe and colleagues were the first to postulate that this disorder was related to the central nervous system (163). Although, credit for reviving interest in laryngeal dystonia as a medical disorder belongs to Dedo with the proposed recurrent laryngeal nerve resection, which was a bold decision at the time when most of his contemporaries still believed in a psychiatric etiology (45).

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