What Is Spasmodic Dystonia? Symptoms, Causes & Treatment

Spasmodic dystonia, also known as laryngeal dystonia, is a neurological voice disorder. It causes involuntary muscle spasms in the larynx, or voice box, which interfere with vocal cord function and disrupt speech. This long-lasting condition typically begins in middle age, often affecting women more frequently than men.

Symptoms and Types of Spasmodic Dystonia

Individuals with spasmodic dystonia commonly experience voice breaks and interruptions in their speech. The voice may sound strained, tight, or breathy, and sometimes a vocal tremor is present. These symptoms can vary in severity daily and may worsen with anxiety, speaking to strangers, or using the telephone. Spasms often subside or disappear when a person laughs, whispers, sings, or speaks at a high pitch.

Spasmodic dystonia is categorized into two main types: adductor and abductor. Adductor spasmodic dystonia is the more prevalent form, accounting for about 85-90% of cases. In this type, the vocal folds involuntarily squeeze together and stiffen during speech. This excessive closing of the vocal cords results in a strained, strangled, or tight voice quality with abrupt voice breaks.

Abductor spasmodic dystonia is less common. Here, involuntary spasms cause the vocal folds to open too widely. When the vocal folds remain open, air escapes during speech, leading to a weak, quiet, breathy, or whispery voice. Some individuals may also experience a mixed type, exhibiting symptoms of both adductor and abductor spasms.

Neurological Origins and Potential Causes

Spasmodic dystonia is a neurological disorder, meaning its origin lies within the brain and nervous system, rather than the vocal cords themselves. While the exact cause remains unknown, it is classified as a focal dystonia, involving abnormal sustained muscle contractions. Research suggests the condition involves abnormal functioning in the basal ganglia, an area deep within the brain responsible for coordinating muscle movements. This dysfunction may involve an imbalance of neurotransmitters.

Genetic factors may also contribute to a predisposition for spasmodic dystonia, with about 12% of affected individuals having a family history of dystonia. While a specific gene has not been definitively identified, research indicates a polygenic contribution, where multiple genetic variants may increase risk. Some cases are linked to mutations in genes like THAP1. Occasionally, symptoms may follow events like a viral infection, head trauma, or significant stress, though a direct causal link has not been scientifically established.

The Diagnostic Process

Diagnosing spasmodic dystonia can be challenging because its symptoms resemble other voice disorders. A comprehensive diagnostic process involves a team of specialists, including an otolaryngologist (ENT) and a neurologist. Diagnosis relies on a thorough medical history and a detailed assessment of the patient’s voice quality.

A key diagnostic tool is laryngoscopy, which involves inserting a flexible tube with a camera through the nose to visualize the vocal folds within the larynx. During this procedure, the physician observes the involuntary muscle movements of the vocal cords as the patient speaks. This visual examination helps rule out other voice problems and identify the characteristic spasms of spasmodic dystonia, which often occur during speech but may be absent during other vocal activities like coughing, breathing, or whispering. While auditory cues are primary in diagnosis, laryngoscopy confirms physical manifestations and aids in differentiating spasmodic dystonia from conditions such as vocal tremor or muscle tension dysphonia.

Available Treatment Approaches

While there is no cure for spasmodic dystonia, various treatment approaches aim to reduce symptoms and improve voice function. The most common and effective treatment involves injections of botulinum toxin (Botox) directly into the affected laryngeal muscles. Botulinum toxin works by temporarily blocking the release of acetylcholine, a neurotransmitter that triggers muscle contractions, thereby weakening the overactive muscles and reducing spasms.

For adductor spasmodic dystonia, Botox is typically injected into the thyroarytenoid or lateral cricoarytenoid muscles. For abductor spasmodic dystonia, it targets the posterior cricoarytenoid muscle. These injections are usually performed in an office setting, sometimes guided by electromyography (EMG) for precise placement. The effects of a single injection are temporary, generally lasting about three months, so repeat injections are necessary to maintain symptom improvement. Patients may experience transient side effects such as breathiness, hoarseness, or difficulty swallowing, which usually resolve within days to weeks.

Voice therapy serves as a complementary approach to botulinum toxin injections, helping individuals manage their symptoms and use their voice more efficiently. A speech-language pathologist can teach exercises designed to improve vocal function, reduce strain, and enhance vocal control. While voice therapy alone may not control the spasms, it can help patients adapt to their voice changes and address any associated anxiety that might worsen symptoms. Surgical options are less common but may be considered for specific cases when Botox injections are ineffective or not well-tolerated. These procedures may include selective laryngeal adductor denervation-reinnervation (SLAD-R) or Type II thyroplasty, which aim to modify nerve pathways or vocal cord positioning.

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