At some point in time, many people will experience problems with their voice. When speaking, words may sound broken, whispery, strangled or hoarse, and a person may struggle just to sound normal. In most cases, these vocal problems eventually go away, but if they don’t then a person may have a type of dysphonia. Dysphonia describes a category of disorders that impair the capacity to create sounds with the vocal organs. One type of dysphonia is a neurological disorder known as spasmodic dysphonia. Another term for this condition is laryngeal dystonia.
Definition & Facts
Dystonia is a neurological movement disorder that can affect the entire body or a specific body part. The primary characteristics of dystonia are involuntary spasms or contractions of muscles. Dystonia disorders are the third most common form of movement disorders behind Parkinson’s disease and essential tremors. There are several types of dystonias including:
- Cervical dystonia – involuntary twist or contortion of the neck
- Blepharospasm – uncontrolled spasm of the eyelids
- Writer’s cramp – involuntary contraction of hand muscles
- Oromandibular dystonia – involuntary muscle spasms of the face or mouth
Spasmodic dysphonia is another type of dystonia that falls into the group of task-specific dystonias where spasms occur only when the muscles are being used. In the case of spasmodic dysphonia, involuntary spasms or contractions of the muscles that control the vocal folds only occur when speaking, not while being silent. Spasmodic dysphonia is often under diagnosed or misdiagnosed, but as many as 50,000 people in North America have this disorder.
Spasmodic dysphonia is sometimes misdiagnosed as muscle tension dysphonia (MTD). Muscle tension dysphonia is characterized by strained speech and occurs when a speaker puts too much pressure on their laryngeal muscles. Unlike spasmodic dysphonia, muscle tension dysphonia is not a neurological disorder.
Symptoms & Complaints
The most common form of dysphonia that affects 80 to 90 percent of people is adductor spasmodic dysphonia where a person will have difficulty pronouncing vowel sounds.
Abductor spasmodic dysphonia is the least common form of spasmodic dysphonia, and it affects 10 to 20 percent of people. Those who have this condition have difficulty pronouncing certain consonants like “f”, “h”, “k”, and “t”. In rare cases, people may suffer from both adductor and abductor dysphonia simultaneously.
Another spasmodic dysphonia condition includes tremors, which affects the muscles outside the larynx and makes the voice sound shaky. Spasmodic dysphonia doesn’t affect emotional or non-verbal speech like laughing, crying, whispering, yelling, or humming, which contributes to the difficulty in diagnosing this condition.
There is no known cause of dystonia conditions, including spasmodic dysphonia, but it is believed that a part of the brain called the basal ganglia, which controls movement, may have something to do with this disorder. The basal ganglia regulates the central nervous system and involuntary muscle movements, but if it gives off the wrong signals or doesn’t work properly, then it could tell the muscles to relax or contract at the wrong moments.
Genetic factors may play a role, and a family history of dystonia may increase the risk of having a dystonia condition such as spasmodic dysphonia. Surgery, psychological stress, traumatic brain injury, viral infections, or any other types of illnesses may play a role in the development of dysphonia, but scientists are currently unable to make a definitive link between these issues and the development of spasmodic dysphonia.
Diagnosis & Tests
Dystonia occurs without any damage or structural changes to the larynx, which makes diagnosing this condition difficult. Spasmodic dysphonia has similar characteristic to other voice disorders, and it is difficult to detect through X-rays, MRIs, or blood tests. There are no tests that can be used to determine if a person has spasmodic dysphonia, so the primary way doctors diagnose the condition is through observation.
A diagnosis is typically made by an otalaryngologist (ENT doctor) who specializes in disorders and diseases of the throat, ears and nose. An otalaryngologist may have additional training in voice disorders, and they tend to work closely with a speech-language pathologist who provide non-medical treatment to someone with spasmodic dysphonia and other voice disorders.
The otalaryngologist and speech pathologist will listen to the patient’s speech to identify any dysphonia symptoms, and they will have the patient read specific sentences that have certain sounds in order to pinpoint the type of spasmodic dysphonia.
The physician will also look to see if there is no other structural damage to the larynx and vocal cords to rule this out as the cause of the voice disorder. This can be done with a flexible tube called an endoscope, or they can give the patient laryngeal electromyography which measures the electrical activity of the muscles in the throat.
Treatment & Therapy
Spasmodic dysphonia is a neurological disorder that has no cure, but there are several treatments that can be used to control the disorder. The most come treatment is to inject botulinum toxin, better known as Botox, into the vocal cord muscles to help those muscles relax. People who have adductor dysphonia may have a selective surgery procedure called laryngeal adductor denervation and rennervation, which essentially repairs the nerve on both sides of the larynx in order to weaken the muscles surrounding the larynx.
Thyroplasty is another surgical procedure that separates the vocal cords limiting their ability to come in contact with each other. This procedure weakens the voice, but it improves speaking fluency. Medications such as benzodiazepines may be given to reduce nervous activities. Examples of such medicines include clonazepam and diazepam. Since spasmodic dysphonia is a neurological condition, speech therapy has minimal effect on the condition but nevertheless may be helpful when used in combination with botulinum toxin or surgery.
Prevention & Prophylaxis