Speech is a complex process that starts with muscle movement, which involves phonation (voice); respiration (breathing process); and articulation (throat, palate, tongue, lips, and teeth).
These muscle movements are initiated, coordinated, and controlled by the brain, and monitored through hearing and touch.
Voice production, or phonation, is generating and modulating sound as part of the speech process.
Voice is created in the vocal cords (or vocal folds) of the larynx.
The larynx, often referred to as the voice box, is a two-inch long tube-shaped organ located in the neck at the top of the trachea (windpipe). The cartilage in front of the larynx is sometimes called the "Adam's apple."
The vocal cords (or vocal folds) are two bands of muscle that form a "V" shape inside the larynx.
The area of the larynx where the vocal cords are located is called the glottis. The area above the cords is called the supraglottis, and the area below the cords is called the subglottis. The epiglottis is a flap at the top of the trachea that closes over the larynx to protect it from food that is swallowed into the esophagus.
Breath enters the body through the nose or mouth, and then travels to the larynx, trachea, and into the lungs. It exits along the same path. Normally, no sound is made by the vocal cords during breathing or exhaling.
When a person talks, the vocal cords tighten, move closer together, and air from the lungs is forced between them. This makes them vibrate and produces sound.
Source: National Institute on Deafness and Other Communication Disorders
Spasmodic dysphonia, also called laryngeal dystonia, is a voice disorder. It is characterized by involuntary spasms or movements in the muscles of the larynx, which causes the voice to break, and have a tight, strained, or strangled sound.
Difficulties that result from spasmodic dysphonia range from occasional problems with saying a word or two to complete inability to communicate.
Spasmodic dysphonia is a chronic condition which most often affects women, particularly between the ages of 30 and 50.
There are three types of spasmodic dysphonia:
- Adductor spasmodic dysphonia
Characterized by sudden involuntary spasms that cause the vocal cords to slam together and stiffen. The spasms interfere with vibration of the vocal cords and production of sound is difficult. Stress can make spasms more severe.
Speech sounds are strained and full of effort. Spasms do not occur when whispering, laughing, singing, speaking at a high pitch, or speaking while breathing in.
- Abductor spasmodic dysphonia
Characterized by sudden involuntary spasms that cause the vocal cords to open. Vibration cannot occur when cords are open so production of sound is difficult. Also, the open position allows air to escape during speech.
Speech sounds are weak, quiet, and whispery. Spasms do not occur when laughing or singing.
- Mixed spasmodic dysphonia
Characterized by symptoms of both adductor and abductor spasmodic dysphonia.
The exact cause of spasmodic dysphonia is not known. Most cases are believed to be caused by a nervous system disorder, and may occur with other movement disorders. Researchers believe it may be caused by abnormal functioning in the basal ganglia of the brain, which helps coordinate movements of muscles throughout the body. Spasmodic dysphonia may be a genetic disorder, or may begin following an upper respiratory infection, injury to the larynx, a long period of voice use, or stress.
In addition to a complete medical history and physical examination, examination of the vocal folds by fiberoptic nasolaryngoscopy may be performed. This procedure involves using a lighted tube, passed though the nose into the larynx to evaluate movement of the vocal folds during speech.
Specific treatment for spasmodic dysphonia will be determined by your physician based on:
- Your age, overall health, and medical history
- Extent of the disease
- Your tolerance for specific medications, procedures, or therapies
- Expectations for the course of the disease
- Your opinion or preference
The goal of treatment is to reduce symptoms of the disorder. Surgery to cut one of the nerves of the vocal fold has been used, as well as counseling. Some success has been achieved with the injection of the botulinum toxin directly into the affected muscles of the larynx. Speech therapy is also an important part of treatment of spasmodic dysphonia.