What is the diagnosis and treatment for spasmodic dysphonia (SD), a neurological disorder affecting speech?

From the Guidelines

Spasmodic dysphonia is a neurological voice disorder that is most effectively treated with botulinum toxin (Botox) injections directly into the affected laryngeal muscles, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery 1. The standard dosage ranges from 1-5 units per injection site, with adductor dysphonia (the most common type) requiring injections into the thyroarytenoid muscles. Some key points to consider in the treatment of spasmodic dysphonia include:

• Botulinum toxin injections are typically administered every 3-4 months by an otolaryngologist 1.
• Speech therapy is recommended as a complementary treatment to help patients develop compensatory voice techniques and manage symptoms between injections 1.
• In severe cases unresponsive to Botox, surgical options like selective laryngeal denervation may be considered 1.
• Patients should be aware that while Botox provides significant relief for most people, temporary side effects may include breathy voice, mild swallowing difficulties, or cough for 1-2 weeks after injection 1. The condition results from dysfunction in the central nervous system's control of laryngeal muscles, specifically in the basal ganglia and related brain regions that coordinate fine motor movements for speech. It is essential to note that the treatment of spasmodic dysphonia should be individualized and based on the specific needs and circumstances of each patient, as outlined in the clinical practice guideline for hoarseness (dysphonia) 1.

From the FDA Drug Label

1. 2 Spread of Toxin Effect Postmarketing safety data from BOTOX Cosmetic and other approved botulinum toxins suggest that botulinum toxin effects may, in some cases, be observed beyond the site of local injection The symptoms are consistent with the mechanism of action of botulinum toxin and may include asthenia, generalized muscle weakness, diplopia, ptosis, dysphagia, dysphonia, dysarthria, urinary incontinence, and breathing difficulties.

The FDA drug label mentions dysphonia as a potential symptom of the spread of toxin effect, but it does not specifically address the treatment of spasmodic dysphonia with onabotulinumtoxinA.

• Spasmodic dysphonia is not explicitly mentioned in the provided drug labels as an approved indication for onabotulinumtoxinA.
• The labels do discuss the potential for dysphonia as an adverse reaction, but this is in the context of the spread of toxin effect rather than the treatment of spasmodic dysphonia.
• Given the lack of direct information, no conclusion can be drawn about the use of onabotulinumtoxinA for spasmodic dysphonia based on the provided drug labels 2, 2.

From the Research

Definition and Symptoms of Spasmodic Dysphonia

• Spasmodic dysphonia (SD) is a neurological voice disorder that causes involuntary spasms of the vocal cord muscles, impacting speech and resulting in strained and strangled voice quality, or weak, quiet, and breathy voice quality 3.
• The disorder is also known as laryngeal dystonia and can be classified into two main types: adductor spasmodic dysphonia and abductor spasmodic dysphonia 3, 4.

Treatment Options for Spasmodic Dysphonia

• The mainstay of management for SD is voice therapy and chemodenervation with botulinum toxin (btx) injections, with surgery being performed in some cases 3, 5.
• Botulinum toxin injections have been widely used to treat both adductor and abductor forms of SD, with vocal improvement noted after treatment for both types 6, 4.
• The efficacy of botulinum toxin for improving vocal symptoms in individuals with SD has been documented in many studies, with results depending on factors such as the general health of the patient, onset and severity of the condition, dosage, interval between injections, and expertise of the practitioner 3, 6, 4.

Botulinum Toxin Injection Techniques

• A national survey of laryngologists found that most participants perform botulinum toxin injections exclusively in the office, with electromyographic (EMG) guidance being the most commonly used technique for adductor SD injections 7.
• The survey also found that the preferred patient position for injections is sitting, and the typical planned interval between injections is 3 to 4 months 7.
• The starting dosage and approach for injections can vary depending on the type of SD and the patient's individual needs, with the most influential factor being the patient's desire/needs, followed by patients' frailty and risk of aspiration 7.

Current Management and Future Directions

• The current standard of care for SD is symptomatic management with botulinum toxin chemodenervation, which has been supported by a large body of literature 5.
• Efforts towards surgical treatment have been made, but the long-term efficacy has not been proven, and further research is expected 5.
• Technological advances have enabled clinicians to better understand the connection between laryngeal function and dysfunction, and refinements in imaging and genetic investigation techniques have helped better understand the underlying mechanisms of SD 5.