Spasmodic dysphonia, or laryngeal dystonia, is a disorder affecting the voice muscles in the larynx, also called the voice box. When you speak, air from your lungs is pushed between two elastic structures—called vocal folds—causing them to vibrate and produce your voice. In spasmodic dysphonia, the muscles inside the vocal fold spasm (make sudden, involuntary movements), interfering with vocal fold vibrations. Spasmodic dysphonia may occur along with other forms of dystonia that cause repeated spasms in other parts of the body, including the eyes, face, jaw, lips, tongue, neck, arms, or legs.
Spasmodic dysphonia causes voice breaks during speaking and can make the voice sound tight, strained, or breathy. In some people, the breaks occur once every few sentences. In more severe cases, spasms may occur on every word, making a person’s speech very difficult to understand. Some people with spasmodic dysphonia may also have vocal tremors—a shaking of the larynx and vocal folds that causes the voice to tremble.
Spasmodic dysphonia is a chronic condition that continues throughout a person’s life. Spasmodic dysphonia may develop suddenly, with severe voice symptoms present from the start of the disorder, or it may start with mild symptoms and occur only occasionally before worsening and becoming more frequent over time.
Spasmodic dysphonia is a rare disorder. It can affect anyone, but the first signs occur most often in people between the ages of 30 and 50. It affects more women than men.
What are the types of spasmodic dysphonia?
- Adductor spasmodic dysphonia is the most common form of spasmodic dysphonia. In this disorder, spasms cause the vocal folds to slam together and stiffen. These spasms make it difficult for the vocal folds to vibrate and produce sounds. The voice of someone with adductor spasmodic dysphonia may sound strained and strangled. The person’s speech may be choppy, with words cut off or difficult to start because of muscle spasms. The spasms are usually absent—and the voice sounds normal—while laughing, crying, or whispering. Stress often makes muscle spasms more severe.
- Abductor spasmodic dysphonia is less common. In this disorder, spasms cause the vocal folds to remain open. The vocal folds cannot vibrate when they are open too far. The open position also allows air to escape from the lungs during speech. As a result, the voice often sounds weak and breathy. As with adductor spasmodic dysphonia, the spasms are often absent during activities such as laughing, crying, or whispering.
- Mixed spasmodic dysphonia, a combination of the above two types, is very rare. Because the muscles that open and the muscles that close the vocal folds are not working properly, it has features of both adductor and abductor spasmodic dysphonia.
What causes spasmodic dysphonia?
Spasmodic dysphonia is thought to be caused by abnormal functioning in an area of the brain called the basal ganglia. The basal ganglia help coordinate the movements of muscles throughout the body. Recent research has found abnormalities in other regions of the brain associated with spasmodic dysphonia, including areas of the cerebral cortex that control commands to muscles and coordinate these commands with incoming sensory information.
In some cases, spasmodic dysphonia may run in families. Although a specific gene for spasmodic dysphonia has not yet been identified, a mutation in a gene that causes other forms of dystonia has also been associated with spasmodic dysphonia.
Symptoms of Spasmodic Dysphonia
A person with dysphonia may experience:
- Breaks or interruptions in speech, often every few sentences
- A hoarse, grating voice that can also sound strained or strangled or hoarse and breathy (known as adductor dysphonia)
- Odd sounding speech that is difficult to understand
- Gradual or sudden difficulty speaking
- The problem may go away when the person laughs, whispers, speaks in a high-pitched voice, sings, or shouts
- Some people have muscle tone problems in other parts of the body, such as writer’s cramp
How is spasmodic dysphonia diagnosed?
Diagnosis of spasmodic dysphonia can be difficult because the symptoms are often similar to those of other voice disorders. Diagnosis usually follows examination by a team, including:
The clinical examination in dystonia may exhibit involuntary writhing/twisting movements precipitated by specific voluntary movements, such as walking or writing. Focal task-specific limb dystonia can begin as painful hand cramping or involuntary wrist/finger spasms when writing, while torticollis presents as an uncontrollable head-turning when driving or watching television.
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Oro-mandibular dystonia can manifest as night-time bruxism (jaw spasms producing forceful jaw closure) and may follow dental procedures, oro-mandibular-facial trauma, or temporomandibular joint dysfunction.
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Spasmodic dysphonia can commence as a strained voice. Despite the name dystonia, the tone of affected extremities at rest is often normal at the onset. Deep tendon reflexes may also be normal.
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A tremor in a patient with dystonia (dystonic tremor) is sometimes distinguished from other tremor types by the presence of a null point (e.g., a neutral position at which the tremor attenuates).
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In cervical dystonia, head tremor sometimes decreases with the head held in a specific position, and displacement from that position, such as turning the head to one side, may worsen it.
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Dystonic tremor may be nonuniform in amplitude and frequency, can be linked with myoclonus (jerk-like movements), and disappears in sleep. Dystonia may cause hypertrophy and pain in affected muscles such as the sternocleidomastoid in spasmodic torticollis.
In its early stages, it may be viewed as an annoying mannerism or hysteria, and only later due to unremitted postural abnormality, lack of the typical psychological characteristics of hysteria, and becoming an apparent feature of the illness, the correct diagnosis is made.
Dystonic movements tend to be exacerbated by fatigue, stress, and emotional states; they tend to be suppressed with relaxation, hypnosis, and sleep.
- An otolaryngologist is a doctor who specializes in diseases of the ear, nose, throat, head, and neck. The otolaryngologist will pass a small lighted tube through the nose and into the back of the throat—a procedure called fiberoptic nasolaryngoscopy—to evaluate vocal fold anatomy and movements during speech and other activities of the larynx.
- A speech-language pathologist is a health professional trained to evaluate and treat voice, speech, and language disorders. The speech-language pathologist will assess voice symptoms.
- A neurologist, a doctor who specializes in nervous system disorders. The neurologist will evaluate for signs in the brain of dystonia and other movement disorders.
What treatment is available for spasmodic dysphonia?
There is currently no cure for spasmodic dysphonia, but treatment can help reduce its symptoms. The most common treatment is the injection of very small amounts of botulinum toxin directly into the affected muscles of the larynx. Botulinum toxin is produced by Clostridium botulinum, the same bacterium found in improperly canned foods and honey. The toxin weakens muscles by blocking the nerve impulse to the muscle. Botulinum toxin injections generally improve the voice for three to four months, after which voice symptoms slowly return. Reinjections are needed to maintain a good speaking voice. Initial side effects include a temporarily weak, breathy voice and occasional swallowing problems, but these usually improve after a few days to a few weeks. Botulinum toxin injections are more effective with adductor spasmodic dysphonia than with abductor spasmodic dysphonia. They do not help in every case.
Behavioral therapy (voice therapy) may reduce symptoms in mild cases. Voice therapy may work along with botulinum toxin injections to reduce voice strain. Some people may also benefit from psychological counseling to help them accept and live with their voice problems.
Augmentative and assistive devices can help some people with spasmodic dysphonia communicate more easily. Some devices can help amplify a person’s voice, whether in person or over the phone. Computer software and tablet or smartphone apps can be used to translate text into synthetic speech.
Supportive measures such as oxygen or assisted ventilation should be provided immediately if indicated.
Diphenhydramine is used for its anticholinergic effect and central nervous system (CNS) penetration. Intravenous administration is preferred to intramuscular administration due to its faster onset. Typical dosing for diphenhydramine is 50 mg intravenous (IV) in adults and 1 mg/kg up to 50mg IV in pediatric patients. Once the acute dystonic reaction is treated and symptoms improve, diphenhydramine should be administered via the oral route every 6 hours for 1 to 2 days to prevent the recurrence of symptoms.
Benztropine is another anticholinergic medication with significant CNS penetration. Use, however, may be limited due to availability in the emergent setting. IV and intramuscular (IM) routes are of a similar time to the onset of the effect. Typical dosing of benztropine is a single dose of 1 to 2 mg IV followed by 1 to 2 mg by mouth twice a day for up to 7 days to prevent a recurrence. Benztropine use in pediatric patients for acute dystonia is considered off-label.
Second-line therapy with IV benzodiazepines may be considered for patients that fail to respond completely to anticholinergic therapy. IV or IM lorazepam at 0.05 to 0.10 mg/kg or IV diazepam at 0.1 mg/kg may be considered.
The medications that are most potent in the treatment of dystonia include anticholinergics (trihexyphenidyl), GABA agonists (baclofen and benzodiazepines), and dopaminergic agents. The mechanism of action of these drugs is due to modifications in dopaminergic and cholinergic neurotransmission and reduced GABA-mediated inhibition in the dystonic central nervous system (CNS).
Trihexyphenidyl is the first-line medication for the management of childhood-onset primary generalized or segmental dystonia.
Focal dystonia can be effectively treated with botulinum toxin injections. The toxin blocks the vesicular release of acetylcholine into the neuromuscular junction, generating temporary local chemo-denervation and muscle weakness, lessening the excessive activity of the affected dystonic muscles.
Botulinum toxin is the first-line treatment for cervical dystonia and blepharospasm and is also habitually used to treat laryngeal dystonia (spasmodic dysphonia), and focal limb dystonia. Apart from its direct peripheral effect of weakening affected muscles, botulinum toxin injections may also reduce afferent feedback from affected muscles, possibly normalizing the abnormal plastic changes in the CNS.
Patients who experience respiratory symptoms or required supportive oxygen should be observed for 12 to 24 hours following the resolution of symptoms to monitor for recurrence.
When more conventional measures have failed, surgery may be performed on the larynx. Several surgical approaches are used to treat spasmodic dysphonia. Some surgical treatments show overall positive outcomes, but the results are not the same for all individuals. To date, no comparative studies are pointing to a single, best treatment.
A physician can explain the potential outcomes, risks, and benefits of surgical treatment and can help to manage expectations.
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