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
How is SD diagnosed?
No Specific Test for Diagnosis
There is no specific test to diagnose SD.
- Diagnosis is based on the patient’s description of the symptoms, the sound of the voice, and the physician’s observation of the vocal folds during speech.
- For this reason, the physician will likely take a detailed history that touches on the features of the disorder mentioned in the previous section.
- In addition, a patient may be asked about associated neurologic symptoms, such as weakness or tremor, and about the use of certain medicines or drugs that have been associated with movement disorders. These include anti-psychotic medications, neuroleptic medications, and illegal intravenous drugs.
As part of the physical examination, a patient may be asked to repeat certain phrases designed to bring out voice breaks.
- Because SD is a central nervous system disorder, the physical exam should include a careful neurologic examination. Some otolaryngologists will ask that a person with suspected SD see a neurologist for this exam.
Fiberoptic Laryngoscopy – Visualizing the Voice Box in Action
The most important part of the examination is observation of the vocal folds during speech using a flexible fiberoptic laryngoscope inserted through the nose.
- The vocal folds will demonstrate the abnormal behavior typical of SD as the patient speaks.
- This part of the examination serves to distinguish SD from conditions that can cause similar voice changes.
(For more information, see Laryngoscopy/Stroboscopy.)
Acoustic and Aerodynamic Measurements
In addition to a careful history and physical examination, some otolaryngologists may use acoustic and aerodynamic measurements and/or electromyography to help diagnose unusual cases.
It is important to understand that there is no specific finding on any test that identifies SD. Although these tests may be helpful, the diagnosis of SD is ultimately a matter of expert opinion based on information gathered from the patient history, physical examination, and, most importantly, the otolaryngologist’s assessment of the nature of the sound of speech.
Cautionary Notes in Diagnosing SD
Ruling Out a Generalized Neurological Disease
Once a diagnosis of SD is made, limited further testing may be performed to eliminate the possibility of associated neurologic conditions. These tests may include:
- Imaging of the brain (usually by magnetic resonance imaging [MRI] with gadolinium)
- Blood tests (to check blood levels of thyroid stimulating hormone [TSH], homocysteine, B12 and folate)
In the overwhelming majority of cases, the results of these studies will prove normal
Wilson’s Disease May Mimic Spasmodic Dysphonia
- A disorder of copper metabolism (Wilson’s disease) can present with symptoms similar to spasmodic dysphonia.
- This disorder can be distinguished from SD by doing a blood test. Patients with Wilson’s disease will have increased blood levels of copper and ceruloplasmin.
SD Must Not Be Confused With Psychiatric or Psychological Disorders
- The symptoms of SD are so variable and some compensatory behaviors so unusual that a psychological or psychiatric disorder might be the first thing that comes to mind – for both family and professionals.
- Patients must seek medical consultation with a specialized voice doctor.
- Beyond question, SD is a physical disorder of the motor processing centers of the brain, not a psychological problem.
- Although psychiatric or psychological intervention sometimes is suggested in managing the anxiety that often makes symptoms worse, it is not a useful treatment for SD.
SD May Be Mistaken for Essential Vocal Tremor
Ad-SD can also be confused with essential vocal tremor. They must be distinguished from each other since their treatment interventions are different. Key features that differ between SD and essential voice tremor are presented in the following table.
Differences Between Adductor Spasmodic Dysphonia and Voice Tremor
|Ad-SD: “closure type”
Strained, strangled voice
“Wobbly” or “shaky” voice
|Pattern of Voice Breaks||Voice breaks and stops are irregular||Voice breaks and stops occur with rhythmic regularity|
|Voice Activity Affected||Voice breaks and stops usually occur only in conversational speech||Voice breaks and stops occur in all types of voice activity: speech, singing, sustained vowels|
|Muscles Involved||Involuntary movements are limited to the muscles of the vocal folds||Involuntary movement affects vocal fold muscles, muscles of the throat and neck strap muscles|
|Role of Medications||Medications helpful to patients with voice tremor have little benefit in SD||Tremor is primarily treated with medications|
In approximately one-third of SD cases, dystonic tremor occurs. This is a combination of spasmodic dysphonia with tremor, which can make the diagnosis confusing.
Ad-SD Can be Mistaken for Muscle Tension Dysphonia
The squeezing together (hyperadduction) of the vocal folds that is the hallmark of muscle tension dysphonia is very similar to that of SD.
- SD is, by definition, spasmodic, meaning that squeezing is irregular; with dysphonia, however, squeezing is generally sustained in muscle tension.
- This distinction can be unclear; in some cases a physician may elect to proceed with treatment for one disorder or the other, using the outcome of treatment to arrive at a definite diagnosis.
- The primary treatment for muscle tension dysphonia is voice therapy, which is only of limited benefit to patients with SD when used as a sole treatment modality.
- For instance, a person with Ab-SD may unconsciously learn to squeeze the vocal folds together tightly to counteract their tendency to move apart so that the appearance of the larynx resembles that of Ad-SD.
- Sequential examinations, or even a trial of treatment, may help in making the diagnosis.
When this occurs, the patient’s speech has both spasmodic speech breaks during speech (SD) and a tremulous “wobble” or “shake” to the voice.
Most physicians believe the muscle tension dysphonia is the body’s attempt to compensate for SD. The concurrent presence of these two disorders can make the diagnosis of SD difficult.
- The primary disorder will usually become evident after an otolaryngologist takes a careful history, listens to the voice, and performs a physical examination. An evaluation by a speech language pathologist or a brief trial of voice therapy may be recommended.
- Patients with SD as the main problem will not significantly improve with voice therapy as the sole treatment, while those with muscle tension dysphonia will benefit from voice therapy.
Stroboscopy via a rigid telescope inserted through the mouth is an extremely useful examination in most cases of voice disturbance, but it may “mask” a case of SD.
Reason: Examination with a rigid telescope requires the examiner hold the patient’s tongue out of the mouth. Sometimes, holding the tongue causes the behavior of the voice box muscles to change such that they do not undergo involuntary movements or spasms. (For more information, see Laryngoscopy/Stroboscopy.)
As with other voice disorders caused by a problem in the nerves and/or brain, the larynx should be examined under conditions that least disturb normal speech activity. Flexible fiberoptic examination through the nose will prove the most reliable exam, since the patient can speak and sing during the examination.
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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