Spasmodic Dysphonia (SD)
A voice disorder resulting from involuntary movements (spasms) of the voice box muscles.
A nervous system problem that causes involuntary movement; dystonia is not a psychological problem; SD is a type of dystonia
Adductor SD (Ad-SD)
Spasms in muscles that close vocal folds, which interrupt speech and cause strained or strangled voice breaks
Abductor SD (Ab-SD)
Spasms in muscles that open vocal folds, which interrupt speech and cause breathy or soundless voice breaks
What is spasmodic dysphonia (SD)?
Spasmodic dysphonia (SD) is a voice disorder in which abrupt, involuntary movements (spasms) in the voice box cause abnormal voice (dysphonia).
Spasmodic dysphonia (SD) is a type of dystonia, a class of disorders caused by problems in the part of the brain that controls movement, resulting in involuntary movements in the affected body part.
A Note on Dystonias
- Dystonias can affect the entire body (generalized dystonia) or just one part (focal or segmental dystonia).
- SD is a focal dystonia that is limited to the voice box (larynx).
- Examples of other focal dystonias include blepharospasm (involuntary eye blinking) and torticollis (wry neck).
- Among neurologists, SD is known as focal laryngeal dystonia.
- Spastic dysphonia is an older term that is synonymous with spasmodic dysphonia.
Three Types of Spasmodic Dysphonia
1. Adductor Spasmodic Dysphonia (Ad-SD)
Most common type: 85 to 90 percent of cases
Affects muscles that bring together (adduct) the vocal folds during speech
2. Abductor Spasmodic Dysphonia (Ab-SD)
Affects the muscles that move apart (abduct) the vocal folds during speech
3. Mixed Spasmodic Dysphonia
Has components of both Ad-SD and Ab-SD
(For more information, see Anatomy & Physiology of Voice Production.)
Usually Not Part of Serious Neurologic Disease
Spasmodic dysphonia usually occurs by itself, and is very rarely associated with other, more serious neurologic diseases.
How does spasmodic dysphonia affect voice?
Voice production depends on precise vocal fold closure and vibratory capacity. The voice box muscle spasms that characterize spasmodic dysphonia alter the precise closure of vocal folds during speech.
- When spasms result in closing or squeezing the vocal folds tight as in Ad-SD, a strained, strangled voice results as the patient strains to force air to produce vocal fold vibration.
- When spasms during speech cause vocal folds to open when they should be closed as in Ab-SD, a loss of sound or a breathy sound results.
- When no spasms occur, the patient’s voice is normal.
What are other common observations in patients with SD?
- Thirty-Something Group
- SD usually affects adults. Symptoms typically begin in the 30s, although onset earlier or later in life is not unusual.
Usually Identified in Women
- Women are more often affected than men.
No Known Hereditary Component
- Although SD has been diagnosed in all ethnic groups and does not seem to be hereditary, there is a greater incidence of SD in Caucasians who are of the Ashkenazi Jewish ethnic background.
In both Ad-SD and Ab-SD, voice interruption (“breaks”) or spasms in the voice occur irregularly. The voice will usually break on specific sounds and parts of the word, such as “t” and “p” sounds followed by a vowel (a, e, i, o, u).
For example, when an Ab-SD patient says the sentence “Pay Paul a penny,” a breathy, voice break will usually occur immediately after each “P”.
Who is likely to develop SD?
No Known Risk Factors
There do not appear to be any behaviors or environmental factors that increase the chance of contracting SD. Although a gene defect has been found for generalized dystonia, no such component has yet been identified for SD.
What are the causes of SD?
Spasmodic dysphonia, like all focal dystonias, is a disorder of unknown cause.
Problem Likely in One Part of the Brain
Researchers believe abnormal brain cell activity in a part of the brain called the basal ganglia is most likely involved in SD.
Some Anecdotal Associations
Patients with SD have reported the onset of symptoms following:
- Trauma to the head
- Common upper respiratory infections
- Routine intubation for general anesthesia and dental work
However, no clear relationship between any of these conditions and SD exists.
How might you notice SD?
- Effort Speaking in the Beginning
- Most people gradually become aware that their speech is requiring more conscious effort.
- Voice Breaks Follow
- The severity of the voice disturbance may vary considerably in the initial stage of the disorder. Over time, it becomes more consistent.
Voice Problem Is Not Progressive, but Does Not Go Away
- There is no evidence that the disorder worsens over the course of a person’s life.
- Unfortunately, there is also no evidence that it improves or resolves.
- Patients with SD almost never lose completely the ability to communicate.
What are the symptoms of SD?
Spasms of the vocal folds cause the typical voice changes of SD”a strained strangled voice for AD-SD, and breathy or soundless breaks in AB-SD. These are represented below.
- “Smooth” movement of voice box muscles
- Fluid voice
- “Closure Type”: vocal folds come together with too much force, interrupting speech
- Strained, strangled voice
- “Open Type”: vocal folds move apart, interrupting speech
- Breathy or soundless breaks in voice
Mixed Spasmodic Dysphonia: combination of symptoms
Patients with mixed SD have voice changes typical of adductor SD and abductor SD.
- There is no characteristic voice sound for mixed SD, but a careful evaluation of the voice will identify both the strained, strangled voice characteristics of adductor SD and the breathy or soundless voice breaks of abductor SD.
Pattern of Symptoms
Severity of Symptoms Varies
- The severity of the symptoms usually varies from day to day–and even over the course of a single day.
- Sometimes, voice may be normal, while at other times it is abnormal.
Anxiety Usually Worsens Voice Problem
- Anxiety or fatigue causes symptoms to be more noticeable.
- Speaking to strangers, public speaking, or speaking in unaccustomed situations often make symptoms worse, probably because all of these situations increase anxiety.
Telephone Conversations Tough
- Most people with SD report that using the telephone is especially difficult.
Being Calm Can Improve Symptoms
- Symptoms are usually mildest in familiar situations.
- A glass of wine or beer can improve symptoms.
Voice Problems are Task-Specific
SD, like most focal dystonias, is task-specific. Voice problems occur only during specific voice tasks.
- In the case of SD, this is virtually always conversational speech.
- The singing voice may remain normal.
Other Symptom Patterns
- Sometimes, symptoms will disappear in highly emotional situations, such as when the affected person is extremely upset, angry, or laughing.
- Swallowing and breathing, the other important functions of the larynx, are almost never affected.
Patient education material presented here does not substitute for medical consultation or examination, nor is this material intended to provide advice on the medical treatment appropriate to any specific circumstances.
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