Anatomy of the Condition:
Dystonia is the overall term used to describe neurological disorders which cause involuntary muscle movements.  Spasmodic dysphonia is a form of dystonia that produces involuntary spasms of the vocal folds, which results in disordered speech

There are two typical forms of spasmodic dysphonia.

• Adductor type is the most common form and is caused by the abrupt
  involuntary contraction of the muscles that bring the vocal folds
  together.  This results in a closure of the vocal folds, which gives
  the person broken, strained speech and a tight quality to the voice.
• Abductor type occurs less commonly.  In this type, involuntary contractions occur in the muscles that open the vocal folds and air escapes suddenly, resulting in breathy, whispery voice breaks.

Other less common forms of spasmodic dysphonia have been identified, including a combination of the two types. 

Causes or Contributing Factors
There is no known cause for spasmodic dysphonia.  It is believed to be a neurological disorder and therefore a result of abnormal functioning of the basal ganglia structure in the brain.  Onset occurs without warning or explanation, and is more prevalent among people in the 40 to 50 year old age group - especially women.

Symptoms:
As discussed above, the key symptom for the adductor variety of SD is a halting, interrupted voice pattern.  With the abductor type of SD, the voice has breathy voice breaks.  Other symptoms may include a tight or constricted sounding voice, which is the result of the patient trying to control spasms. Symptoms may also improve or worsen, depending on the time of day.

Diagnosis:
The condition is frequently misdiagnosed or hard to diagnose.  The disease often mimics other conditions or speech patterns, and appropriate diagnosis requires a thorough examination by an experienced team of voice specialists.

There is not a definitive test for the condition.  Diagnosis depends on a combination of symptoms and evaluation by the clinical voice team.

Treatments:

Non-Operative

• Botox Injections: This is one of the most effective treatments in recent years for both major forms of Spasmodic Dysphonia.  The drug has the effect of softening and weakening the vocal muscles so that spasms are diminished.  This treatment also reduces the wispiness associated with the abductor form of the disease.    
  
  The results of Botox may vary, but the drug normally takes effect from 24-48 hours after the injections.  After that, the voice becomes soft and breathy for a period of several days to two weeks. After this, the voice should get stronger and stronger with reduction of spasms.  The duration of the effect is variable but will commonly last for three to four months before the patient will require the next injection.
  
  Since the procedure weakens vocal muscles, an initial side-effect following Botox injections may be difficulty in swallowing. However, a speech pathologist can usually train the patient in alternative swallowing techniques.  
  
• Voice relaxation techniques and other speech therapies may sometimes be effective in lessening some of the symptoms of the condition.

Operative
In some instances, surgery may be recommended and a relatively new surgical option is Selective Laryngeal Adductor Denervation Reinnervation.  In this procedure, the nerves to the muscles bringing the vocal folds together are divided.  Alternate neural tissue is then used to lessen the symptoms of spasmodic dysphonia.