Spasmodic dysphonia

# Overview
Spasmodic dysphonia (or laryngeal dystonia) is a voice disorder characterized by involuntary movements of one or more muscles of the larynx (vocal folds or voice box) during speech.

# Types of spasmodic dysphonia
The three types of spasmodic dysphonia are adductor spasmodic dysphonia, abductor spasmodic dysphonia and mixed spasmodic dysphonia.

## Adductor spasmodic dysphonia
In adductor spasmodic dysphonia, sudden involuntary muscle movements or spasms cause the vocal folds (or vocal cords) to slam together and stiffen. These spasms make it difficult for the vocal folds to vibrate and produce voice. Words are often cut off or difficult to start because of the muscle spasms. Therefore, speech may be choppy and sound similar to stuttering. The voice of an individual with adductor spasmodic dysphonia is commonly described as strained or strangled and full of effort. Surprisingly, the spasms are usually absent while whispering, laughing, singing, speaking at a high pitch or speaking while breathing in. Stress, however, often makes the muscle spasms more severe.

## Abductor spasmodic dysphonia
In abductor spasmodic dysphonia, sudden involuntary muscle movements or spasms cause the vocal folds to open. The vocal folds can not 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.

## Mixed spasmodic dysphonia
Mixed spasmodic dysphonia involves muscles that open the vocal folds as well as muscles that close the vocal folds and therefore has features of both adductor and abductor spasmodic dysphonia.

# Origins
The exact cause of spasmodic dysphonia (SD) is unknown. According to the National Institute on Deafness and Other Communication Disorders "research has revealed increasing evidence that most cases of spasmodic dysphonia are in fact neurogenic or having to do with the nervous system (brain and nerves)." 
.  SD is a neurological disorder rather than a disorder of the larynx, and as in other forms of dystonia, interventions at the end organ (ie, larynx) have not offered a definitive cure, only symptomatic relief. The pathophysiology underlying dystonia is becoming better understood as a result of discoveries in genetically based forms of the disorder, and this approach is the most promising avenue to a long-term solution. 

## Debate about psychiatric versus neurological basis to SD
The National Institute of Neurological Disorders and Stroke (NINDS) and the American Academy of Neurology (AAN) classify SD as a neurological disorder.  .  However, 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. No medical organizations or groups take this position.  A comparison of SD patients compared with vocal fold paralysis (VFP) patients found that 41.7% of the SD patients met the DSM-IV criteria for psychiatric comorbidity compared with 19.5% of the VFP group. However, another study found the opposite, with SD patients having significantly less psychiatric comorbidity compared to VFP patients: "The prevalence of major psychiatric cases varied considerably among the groups, from a low of seven percent (1/14) for spasmodic dysphonia, to 29.4 percent (5/17) for functional dysphonia, to a high of 63.6 percent (7/11) for vocal cord."  .  A review in the journal Swiss Medicine Weekly states that "Psychogenic causes, a 'psychological disequilibrium', and an increased tension of the laryngeal muscles are presumed to be one end of the spectrum of possible factors leading to the development of the disorder". Alternatively, many investigators into the condition feel that the psychiatric comorbidity assoicated with voice disorders is a result of the social isoloation and anxiety that patients with these conditions feel as a consequence of their difficulty with speech, as opposed to the cause of their dysfluency.    The opinion that SD is psychogenic is not upheld by many experts in the scientific community. 

## Evidence for a Neurological basis to SD
SD is formally classified as a movement disorder, one of the focal dystonias, and is also known as laryngeal dystonia.   
Supporting evidence that SD is a neurological disorder includes:
1.  SD may co-occur with other neurological movement disorders such as blepharospasm (excessive eye blinking and involuntary forced eye closure), tardive dyskinesia (involuntary and repetitious movement of muscles of the face, tongue, body, arms and legs), oromandibular dystonia (involuntary movements of the jaw muscles, lips and tongue), torticollis (involuntary movements of the neck muscles), or tremor (rhythmic, quivering muscle movements).  
2.  Spasmodic dysphonia runs in some families and is thought to be inherited. Research has identified a possible gene on chromosome 9 that may contribute to the spasmodic dysphonia that is common to certain families.  
3.  Histological examination of the nerve to the vocal cords in patients with SD demonstrates that the percentage of abnormally thin nerve fibers was higher than in normal controls
4.   Functional MRI signal is reduced in sensorimotor cortices associated with movement of the affected body part in laryngeal dystonia, supporting a dystonic basis for this voice disorder.

# Diagnosis
Unfortunately, diagnosis of spasmodic dysphonia is often delayed due to lack of recognition of its symptoms by screening physicians.  Most patients who are correctly diagnosed are evaluated by a team that usually includes an otolaryngologist, a speech-language pathologist and a neurologist. The otolaryngologist examines the vocal folds to look for other possible causes for the voice disorder. Fiberoptic nasolaryngoscopy, a method whereby a small lighted tube is passed through the nose and into the throat, is a helpful tool that allows the otolaryngologist to evaluate vocal cord movement during speech. The speech-language pathologist evaluates the patient's voice and voice quality. The neurologist evaluates the patient for signs of other movement disorders.

# Treatment
There is no cure for spasmodic dysphonia.
The most effective treatment for reducing the symptoms of spasmodic dysphonia is injections of very small amounts of botulinum toxin (Botox) directly into the affected muscles of the larynx. The toxin weakens muscles by blocking the nerve impulse to the muscle. The botulinum toxin injections generally improve the voice for a period of three to four months after which the voice symptoms gradually return. This treatment requires continual injections to maintain a good speaking voice.
SD is sometimes confused with other hyperfunctional voice disorders that may respond to voice therapy; however, voice therapy is not effective in treating SD.  
An operation that cuts one of the nerves of the vocal folds (the recurrent laryngeal nerve) has improved the voice of many for several months to several years but the improvement is often temporary.
Morton Cooper claims to have been curing the condition for 35 years with a treatment he calls DVR.  His treatments are not widely accepted in the medical community; in response, instead of verifying his results, he alleges that information about spasmodic dysphonia is controlled by Allergan, the maker of Botox, producing a conflict of interest. Mr. Cooper's methods are not subject to peer review and his improvements or cures have not be validated by reputable medical practitioners.

# Notable people with spasmodic dysphonia
- Linda Thompson (singer), British folk-rock musician.
- Scott Adams, the creator of the comic strip Dilbert.
- Robert F. Kennedy, Jr.
- Johnny Bush, country & western musician and songwriter.
- Diane Rehm, an American public radio talk show host.
- Darryl McDaniels of the rap group Run DMC
- Mary Lou Lord