Description
Spasmodic dysphonia is a neurological disorder
affecting the voice muscles in the larynx, or voice box. The muscles inside the vocal folds experience sudden involuntary movements—called spasms-- which interfere with the ability of the folds to vibrate and produce voice. Spasmodic dysphonia causes voice breaks and can give the voice a tight, strained quality. People with spasmodic dysphonia may have occasional breaks in their voice that occur once every few sentences. Usually, however, the disorder is more severe and spasms may occur on every other word, making a person’s speech very difficult for others to understand. At first, symptoms may be mild and occur only occasionally, but they may worsen and become more frequent over time. Spasmodic dysphonia is a chronic condition that continues throughout a person’s life. |
Quick Facts
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Causes
Although the exact cause of SD is unknown, evidence suggests that the problem starts at the base of the brain in the basal ganglia, which regulate involuntary muscle movement. To oversimplify, this nervous system regulator does not function properly and produces incorrect signals, which cause the muscles to contract or relax more than they should or at the wrong time.
Genetic factors may put some people at greater risk of developing spasmodic dysphonia, particularly those who have family members with any form of dystonia. Although 14 genes have been recently associated with various dystonias, only mutations in one gene, named THAP1, have been associated with forms of whole body dystonia that begin in childhood and that appear with spasmodic dysphonia. This genetic defect does not seem to be associated with the more usual form of focal spasmodic dysphonia that begins in adults, however. Spasmodic dysphonia may co-occur with other dystonias that cause involuntary and repetitious movement of such muscles as the eyes; face, body, arms, and legs; jaws, lips, and tongue; or neck. While anecdotal evidence may suggest that symptom onset follows illnesses such as viral infection, head trauma, bronchitis, surgery, or a stressful event, such linkages have not been scientifically proven and the medical community has not reached agreement on whether illness or stress plays any part in the onset of SD. |
Symptoms
People with SD initially notice either a gradual or sudden onset of difficulty in speaking. They may hear breaks in their voices during production of certain words or speech sounds, breathy-sounding pauses on certain words or sounds, or a tremulous shaking of the voice. They may feel that talking requires more effort than before. Often people say that their voices sound as if they “have a cold or laryngitis.” The voice symptoms can begin following an upper respiratory infection, injury to the larynx, or voice overuse. Stress does not cause SD, but it can worsen the spasms. The symptoms of SD can vary from mild to severe. A person's voice can sound strained, tight, strangled, breathy, or whispery. The spasms often interrupt the sound, squeezing their voice to nothing or dropping it to a whisper.
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Nature of Disorder
Relatively little is known regarding the onset, course, and progression of SD, and only a handful of investigations have examined SD symptom development. In a sample of 34 cases of SD, Aronson found that the mean age of SD onset was 44 years. In 94%of those cases, the severity of voice symptoms fluctuated after the initial onset, but the dysphonia never resolved, Brodnitz reported a mean onset age of 50 years In 130 cases of SD, Variability in the course of SD was also observed by Borenstein (unpublished observations, 1978): 2 of 10 individuals reported that their symptoms had worsened during an 18-year period, whereas the remaining 8 reported symptom improvement or plateau, Aronson (unpublished observations, 1979) reported a median onset age of 50 years in 100 cases of SD, with symptoms progressing during the first year after onset. Later, Aronson concluded that SD symptoms often plateau within the first year after onset, although some individuals experience progressive worsening over time. In a group of 29 cases, Schaefer observed that SD symptoms remitted intermittently in the first 2 years after onset, and that symptom severity was variable years after onset, Izdebski examined 200 case histories of patients with SD to identify risk factors for the disease and to characterize symptom onset. The results indicated that 84% of patients reported a gradual onset of voice symptoms.
Types of Spasmodic Dysphonia
Adductor Spasmodic DysphoniaThis is the most common form of spasmodic dysphonia affecting approximately 80–90% of people with Spasmodic Dysphonia. It is characterized by spasms that cause the vocal folds to slam together and stiffen. These spasms make it difficult for the vocal folds to vibrate and produce sounds. Words are often cut off or are difficult to start because of muscle spasms. Therefore, speech may be choppy. Spasms are usually absent—and the voice sounds normal—while laughing, crying, or shouting. Stress often makes the muscle spasms more severe. Spasms occur particularly on “voiced” speech sounds. Examples of “voiced” sounds that cause problems for people with adductor SD include the vowel sounds in the words "eat," "back," "in," "I," "olives," or "nest."In very severe cases of AD, the speaker may need to use extreme effort to produce any voice at all since vowels occur frequently in speech. People with this type often complain of having to struggle to speak.
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Abductor Spasmodic DysphoniaThis type is characterized by spasms that cause the vocal folds to open. It occurs in approximately 10–20 percent of cases. The vocal folds cannot vibrate when they are open too far. The open position also allows air to escape from the lungs during speech. As a result, the voice often sounds weak and breathy. As with adductor spasmodic dysphonia, the spasms are often absent during activities such as laughing, crying, or shouting. The symptoms can range from mild to severe. Significant overall breathiness or a whispered voice quality may occur in people with a very severe form of the disorder where breaks occur on every voiceless consonant. Because people with this type expend too much air as they produce sound, they often describe feeling winded or out-of-breath during speaking.
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Mixed Spasmodic Dysphonia
This is a combination of the other two types and is very rare. Because both the muscles that open and the muscles that close the vocal folds are not working properly, it has features of both adductor and abductor spasmodic dysphonia. This may result in halting speech as well as variable breathiness and tightness.
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Sources:
U.S. Department of Health & Human Services. (2010). NIDCD fact sheet: Spasmodic dysphonia. Retrieved from http://www.google.com/url?sa=t& rct=j&q=&esrc=&source=web&cd=1&cad=rja&uact=8&ved=0CCgQFjAA&url=http%3A%2 %2Fwww.nidcd.nih.gov%2Fstaticresources%2Fhealth %2Fvoice%2FSpasmodicDysphonia.pdf&ei=s5EzU9STCurAyAGrxYFAusg=AFQjCNEP26yRSMGTG3Qc1DfUlNQijmOl5w&bvm=bv.63808443,d.aWc.
National Spasmodic Dysphonia Association. (2014). Symptoms. Retrieved from http://www.dysphonia.org/symptoms.php.
Cleveland Clinic. (2014). Diseases and conditions: Spasmodic dysphonia. Retrieved from http://my.clevelandclinic.org/head-neck/diseases-conditions/hic-spasmodic-dysphonia.aspx.
Arch Health Partners. (2012). Spasmodic dysphonia. Retrieved from http://www.archhealth.org/archcontentpage.aspx?nd=1354
Baylor College of Medicine. (1998-2013). Spasmodic dysphonia (sd). Retrieved from https://www.bcm.edu/healthcare/care-centers/parkinsons/conditions/spasmodic-dysphonia
Tanner, K., Roy, N., Merrill, R., Sauder, C., Houtz, D., & Smith, M. (2011). Spasmodic dysphonia: Onset, course, socioemotional effects, and treatment response. Annals of Otology, Rhinology, & Laryngology, 120(7), 465-473.
U.S. Department of Health & Human Services. (2010). NIDCD fact sheet: Spasmodic dysphonia. Retrieved from http://www.google.com/url?sa=t& rct=j&q=&esrc=&source=web&cd=1&cad=rja&uact=8&ved=0CCgQFjAA&url=http%3A%2 %2Fwww.nidcd.nih.gov%2Fstaticresources%2Fhealth %2Fvoice%2FSpasmodicDysphonia.pdf&ei=s5EzU9STCurAyAGrxYFAusg=AFQjCNEP26yRSMGTG3Qc1DfUlNQijmOl5w&bvm=bv.63808443,d.aWc.
National Spasmodic Dysphonia Association. (2014). Symptoms. Retrieved from http://www.dysphonia.org/symptoms.php.
Cleveland Clinic. (2014). Diseases and conditions: Spasmodic dysphonia. Retrieved from http://my.clevelandclinic.org/head-neck/diseases-conditions/hic-spasmodic-dysphonia.aspx.
Arch Health Partners. (2012). Spasmodic dysphonia. Retrieved from http://www.archhealth.org/archcontentpage.aspx?nd=1354
Baylor College of Medicine. (1998-2013). Spasmodic dysphonia (sd). Retrieved from https://www.bcm.edu/healthcare/care-centers/parkinsons/conditions/spasmodic-dysphonia
Tanner, K., Roy, N., Merrill, R., Sauder, C., Houtz, D., & Smith, M. (2011). Spasmodic dysphonia: Onset, course, socioemotional effects, and treatment response. Annals of Otology, Rhinology, & Laryngology, 120(7), 465-473.