Spasmodic dysphonia (SD), also known as laryngeal dystonia, is a disorder in which the muscles that generate a person’s voice go into periods of spasm.
Spasmodic dysphonia results in breaks or interruptions in the voice, often every few sentences, which can make a person difficult to understand.
The person’s voice may also sound strained or they may be nearly unable to speak.
Onset is often gradual and the condition is lifelong.
Its cause is unknown.
Risk factors may include family history.
Triggers of SD may include an upper respiratory infection, injury to the larynx, overuse of the voice, and psychological stress.
The underlying abnormality is believed to typically involve the central nervous system, specifically the basal ganglia.
There is no cure.
Treatment may improve symptoms, and most commonly this involves injecting botulinum toxin into the affected muscles of the larynx.
injecting botulinum toxin generally results in improvement for a few months.
Other measures include voice therapy, counselling, and amplification devices.
Evidence to support surgery is limited,[1] some have recovered following surgery.
The disorder affects an estimated 2 per 100,000 people, and women are more commonly affected.
Onset is typically between the ages of 30 and 50.
Severity is variable, in some, work and social life are affected.
Life expectancy is normal.
Symptoms of SD can come on suddenly or gradually appear over the span of years.
Symptoms of SD can come and go for hours or even weeks at a time, or remain consistent.
Gradual onset can begin with hoarse voice quality, which may later transform into a voice quality described as strained with breaks in phonation.
Voice symptoms are less likely to occur at rest, while whispering, or on speech sounds that do not require phonation.
This occurs because of an increase in sporadic, and prolonged tension found in the muscles around the larynx during phonation.
This tension affects the abduction and adduction of the vocal folds, and the vocal folds are unable to retain subglottal air pressure required for phonation.
The breaks in phonation can be heard throughout the speech of people with spasmodic dysphonia.
The voice quality of adductor spasmodic dysphonia can be described as strained or strangled from tension in the glottal region.
Symptoms of spasmodic dysphonia typically appear in middle-aged people, but have also been seen in people in their twenties, with symptoms emerging as young as teenage years.
Risk factors include:
Being female
Being middle aged
Having a family history of neurological diseases-tremor, dystonia, meningitis, and other neurological diseases.
Experiencing stressful events
Upper respiratory tract infections
Sinus and throat illnesses
Heavy voice use
Cervical dystonia
Childhood measles or mumps
Pregnancy and parturition
Evidence of a genetic contribution for dystonia involving the larynx is weak.
SD is a neurological disorder rather than a disorder of the larynx.
Interventions at the end organ, larynx, have not offered a definitive cure, only symptomatic relief.
Because the voice can sound normal or near normal at times, some practitioners believe it to be psychogenic; that is, originating in the affected person’s mind rather than from a physical cause, but opinion that SD is psychogenic is not upheld by experts in the scientific community.
SD is formally classified as a movement disorder.
Diagnosis
There is currently no universally accepted diagnostic test for spasmodic dysphonia, which presents a challenge for diagnosis.
A speech–language pathologist, an otolaryngologist, and a neurologist, are typically involved in spasmodic dysphonia assessment and diagnosis.
Differential diagnosis Because spasmodic dysphonia shares many characteristics with other voice disorders, misdiagnosis frequently occurs.
Muscle tension dysphonia, a functional voice disorder that results from use of the voice, rather than a structural abnormality.
Being able to differentiate between muscle tension dysphonia and spasmodic dysphonia is important because muscle tension dysphonia typically responds well to behavioral voice treatment, but spasmodic dysphonia does not.
The are three types of spasmodic dysphonia:adductor spasmodic dysphonia, abductor spasmodic dysphonia, and mixed spasmodic dysphonia.
A fourth type called whispering dysphonia has also been proposed.
Adductor spasmodic dysphonia is the most common type, affecting around 87% of individuals with SD.
Adductor spasmodic dysphonia (ADSD) is the most common type, affecting around 87% of individuals with SD.
In ADSD, sudden involuntary muscle movements or spasms cause the vocal folds (or vocal cords) to squeeze together and stiffen.
These spasms occur in the adductor muscles of the vocal folds, specifically the thyroarytenoid and the lateral cricoarytenoid, making 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.
The voice of an individual with adductor spasmodic dysphonia is described as strained or strangled and full of effort.
The spasms are usually absent while laughing, speaking at a high pitch, or speaking while singing, but singers can experience a loss of range or the inability to produce certain notes of a scale or with projection.
Stress, however, often makes the muscle spasms more severe.
Abductor spasmodic dysphonia (ABSD) is the second most common type of spasmodic dysphonia affecting around 13% of individuals with SD.
In ABSD, sudden involuntary muscle movements or spasms cause the vocal folds to open.
These 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.
As with adductor spasmodic dysphonia, the spasms are often absent during activities such as laughing or singing, but singers can experience a loss of range or the inability to produce certain notes of a scale or with projection.
Mixed spasmodic dysphonia is the most rare 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.
Whispering dysphonia appears to be caused by mutations in the TUBB4 gene on the short arm of chromosome 19.
This gene encodes a tubulin gene.
Potential treatments for spasmodic dysphonia, include botulinum toxin,voice therapy, and surgery.
Anticholinergics have been found to be effective in 40–50% of people, but which are associated with a number of side effects.
Botulinum toxin Botulinum toxin is often used to improve some symptoms of spasmodic dysphonia through weakening or paralyzing the vocal folds, thus preventing muscle spasms.
It has high predictability and low chance of long term side effects.
It results in periods of some improvement, with the duration of benefit lasting for 10–12 weeks on average.
Voice therapy appears to be ineffective in cases of true spasmodic dysphonia, but it is difficult to distinguish between spasmodic dysphonia and functional dysphonias, and misdiagnosis is relatively common.
Evidence to support surgery as a treatment for SD is limited.
Post-surgery voices can be imperfect and about 15% of people have significant difficulties.
Surgical approaches include recurrent laryngeal nerve resection, selective laryngeal adductor denervation-reinnervation (SLAD-R), thyroplasty, thyroarytenoid myectomy, and laryngeal nerve crush.
Recurrent laryngeal nerve resection involves removing a section of the recurrent laryngeal nerve.
Recurrent laryngeal nerve avulsion is a removal of sections of the nerve and has positive outcomes of 80% at three years.
SLAD-R is effective specifically for adductor spasmodic dysphonia, for which it has shown good outcomes in about 80% of people at 8 years.
Thyroplasty changes the position or length of the vocal folds.