Laryngeal Dystonia

Laryngeal Dystonia

Overview

Laryngeal dystonia (LD) is a chronic voice disorder characterized by spasms of the muscles of the voice box (larynx). These muscles control the voice. The spasms can result in tightness in the throat, recurrent hoarseness, and changes in voice quality and/or difficulty speaking. The most frequent sign of this disorder is a sudden, momentary lapse or interruption of the voice. When affected individuals speak, their voice may sound strained, forced, strangled, breathy, or whispery. Speaking becomes less natural, and often requires great effort. In severe cases, an affected individual may be barely able to speak. LD can potentially cause significant quality of life issues for affected individuals impacting both work and social situations. There is no cure for LD, but the disorder can be treated. In most cases, the cause of LD is not known.

LD is a form of dystonia, a group of movement disorders that vary in their symptoms, causes, progression, and treatments. This group of conditions is generally characterized by involuntary muscle contractions that cause abnormal movements and positions (postures). LD is classified as a focal dystonia because it affects a specific part of the body (muscles of the voice box). The most common type of LD is spasmodic dysphonia (SD).

Symptoms

The severity of LD can fluctuate from symptom-free periods with normal voice to severely disabling periods where an affected individual will experience significant difficulty speaking clearly or be barely able to speak. Symptom fluctuation can occur during the same day or from day to day or longer. LD tends to affect normal conversational speech. Several studies have shown that singing, laughing, and yelling, are often unaffected.

The two most common types of LD are adductor SD and abductor SD. Adductor SD, the more common type, affects approximately 80% to 90% of individuals. This type affects the muscles that draw the vocal cords together. Adductor SD is characterized by a tight, strained, or harsh sounding voice. Affected individuals may experience difficulties in the voicing of specific vowels sounds such as in the words “eat,” “back,” “I,” “olives,” or “nest”.

Abductor SD affects the muscles that draw the vocal cords apart. Abductor SD is characterized by breathy, whispered speech and loss of voice for short periods of time (aphonia). Individuals affected by the abductor type may have difficulty controlling speech after certain sounds (e.g., “h,” “s,” “p,” “t,” or “k”).

Some affected individuals may exhibit both types, referred to as mixed SD. Some individuals also experience a vocal tremor, in which the larynx and vocal cords shake potentially affecting speech and making the voice difficult to understand because it sounds shaky or quivery. Other less common manifestations of LD include laryngeal breathing dystonia, singer’s dystonia, repetitive coughing, and others.

Onset of LD is usually gradual and the initial symptoms may be mild. Symptoms may progress for the first 2-5 years then generally stabilize. Approximately 15% of patients progress into other forms of dystonia involving the face or neck. The disorder usually remains chronic without marked changes over a period of years, although symptoms may worsen with stress. The number and severity of symptoms varies widely among affected individuals.

Causes

Most cases of LD are idiopathic, which means a cause is not identifiable. Several different factors may be involved in the development of the disorder (multifactorial). Several theories exist that attempt to explain the underlying mechanisms of LD including abnormal functioning of portions of the brain involved in muscle control, or imbalances in neurotransmitters. Neurotransmitters are chemicals that modify, amplify, or transmit nerve impulses from one brain cell (neuron) to another, enabling nerve cells to communicate. Although the underlying mechanisms and causes of LD are not well understood, research is ongoing to determine the specific roles that genetic, environmental, and other factors ultimately play in the development of the disorder.

There are reports in the medical literature that suggest LD may develop following specific factors such as an upper respiratory infection or bronchitis, trauma or surgery, or exposure to certain drugs and/or toxins. However, such theories are controversial because there is no scientific evidence conclusively linking these factors to LD.

Genetic factors are believed to play a role in some cases, especially in individuals who have a relative with LD or another form of dystonia. These individuals may have a genetic susceptibility to developing the disorder. A person who is genetically predisposed to a disorder carries a gene (or genes) for the disease, but the disorder may not be expressed unless it is triggered or activated by other genetic modifiers or environmental factors (complex genetics). More research is necessary to determine what role this or other genes have in the development of LD.

Affected populations

LD occurs more often in females than males and can affect individuals of all ethnic backgrounds. Onset can occur at any age, but usually occurs between 30 and 60 years of age. The exact incidence or prevalence of the disorder is unknown. LD is estimated to affect approximately 50,000 people in North America. However, determining the true frequency of LD in the general population is difficult because many cases are misdiagnosed or go undiagnosed.

Disorders with Similar Symptoms

Symptoms of the following disorders can be similar to those of LD. Comparisons may be useful for a differential diagnosis:

Muscle tension dysphonia is a condition characterized by hoarseness or a strained, rough quality of the voice. Symptoms may become progressively worse with use and improve with rest (i.e. not speaking). Muscle tension dysphonia is caused by abnormal contractions of the muscles of the voice box that control the voice. It is common in individuals who use their voice frequently and may result from straining, squeezing, or pushing these muscles inappropriately. Although LD and muscle tension dysphonia are considered separate disorders, it can be difficult to tell them apart, even for experts. Some experts believe that symptoms of LD and muscle tension dysphonia can co-occur. However, unlike LD, muscle tension dysphonia is reversible with voice therapy.

LD is often combined with tremor (probably more than 40% of patients have both). Tremors are neurological disorders characterized by rhythmical shaking of a body region, most often of the hands or arms. Tremor may be seen as involuntary shaking or trembling of the affected area. Other motor symptoms may be present including an unsteady manner of walking due to an inability to coordinate voluntary movements (ataxia). The primary symptom is a fine or coarse rhythmic tremor that occurs approximately 4 to 12 times per second. In some people, tremor may affect the tongue and/or the vocal cords, leading difficulty speaking (dysarthria). It can also affect the muscles of the neck, causing the head to shake. The exact, underlying cause of most tremors is not fully understood and is most likely multifactorial, which means that several factors, such as genetic and environmental ones, all play a role in the development of the disorder. The rhythmical sound of voice tremor is sometimes difficult to distinguish from the semi-rhythmical voice interruptions in LD (For more information, choose “essential tremor” as your search term in the Rare Disease Database.)

Chronic stuttering is a common speech disorder characterized by an abnormal speech pattern that is composed of repetitions, prolongations, and unusual hesitations that disrupt the rhythmic flow of speech. Affected children usually know what they want to say, but have difficulty or are unable to say it. The disorder usually appears before age 12 and often affects more than one family member (familial). Although stuttering usually resolves on its own (spontaneously) before adolescence, it can persist into adulthood. Most likely, chronic stuttering is caused by a variety of factors.

Diagnosis

The diagnosis of LD usually involves careful assessment of the voice and speaking under different conditions by a speech pathologist, otolaryngologist, or neurologist. It also includes inspection of the voice box (laryngoscopy) to rule out structural abnormalities of the vocal cords such as nodules, polyps, or tumors.

Standard Therapies

Treatment

There is no cure for LD. Treatment is aimed at the symptoms in each individual. Psychological support and counseling can help individuals cope with depression, anxiety or other psychological issues associated with LD.

Botulinum toxin therapy is often used for LD. The drug works by blocking nerve activity that controls muscles. The result is that muscle activity is not as strong. The drug is injected into the vocal cords every three or four months. Some individuals can wait longer between injections before symptoms return and more injections are needed. The degree of effectiveness of Botulinum toxin will differ in each individual case. Botulinum toxin is approved by the Food and Drug Administration (FDA) for some types of dystonia, but not LD. However, it is widely used off label to treat all forms of dystonia.

Speech or voice therapy such as voice relaxation techniques may be beneficial for some individuals with LD, especially those with mild cases of the disorder. Speech or voice therapy may also be effective in treating side effects associated with other treatments such as Botulinum toxin (adjuvant therapy). Some individuals may benefit from using machines or devices that amplify the voice.

Oral medications have been used to treat forms of dystonia such as LD. However, there are no oral medications that are FDA approved for such use. Such medications include dopaminergic agents (levodopa), anticholinergic agents (benztropine, trihexyphenidyl), baclofen, and clonazepam. These drugs act in various way to reduce muscle or nerve activity, but are often associated with side effects.

If other therapeutic options are ineffective, contraindicated, or no longer effective after initially providing relief, then surgery may be recommended. Surgery may be aimed at separating the vocal cords or weakening the affected muscles of the larynx. Specific procedures include thyroplasty or selective laryngeal adductor denervation-reinnervation.

Decisions concerning the use of particular drug regimens and/or other treatments such as surgery should be made by physicians and other members of the health care team in careful consultation with parents or a patient based upon the specifics of an individual case; a thorough discussion of the potential benefits and risks, including possible side effects and long-term effects; patient preference; and other appropriate factors.

Type of Doctor Department : Speech Pathology., Otolaryngologist, Neurologist