Headache & Pain
Oct. 11, 2020
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Spasmodic dysphonia belongs to a family of neurological disorders called dystonias. A dystonia is a movement disorder that causes muscles to contract and spasm involuntarily. Dystonias can be generalized, affecting the entire body, or focal, affecting only a specific area of the body or group of muscles. Following Parkinson’s disease and essential tremor, dystonia is the third most common movement disorder. The most common focal dystonia, cervical dystonia, causes the neck to twist or contort. Other dystonias can cause abnormal, involuntary blinking or spasm of the eyelids (blepharospasm), inappropriate contractions of the hand muscles (writer’s cramp), or uncontrolled movements from spasms in any of the muscles of the face, jaw, or tongue (oromandibular dystonia).
Certain dystonias, including SD, are task-specific, meaning that the muscles spasm only when they are used for particular actions and not when they are at rest. When a person with SD attempts to speak, involuntary spasms in the tiny muscles of the larynx cause the voice to break up, or sound strained, tight, strangled, breathy, or whispery. The spasms often interrupt the sound, squeezing the voice to nothing in the middle of a sentence, or dropping it to a whisper. However, during other activities, such as breathing and swallowing, the larynx functions normally.
Spasmodic dysphonia is estimated to affect approximately 50,000 people in North America, but this number may be somewhat inaccurate due to ongoing misdiagnosis or undiagnosed cases of the disorder. Although it can start at any time during life, SD seems to begin more often when people are middle-aged. The disorder affects women more often than men. Onset is usually gradual with no obvious explanation. Symptoms usually occur in the absence of any structural abnormality of the larynx, such as nodules, polyps, carcinogens, or inflammation. People have described their symptoms as worsening over an approximate 18-month period and then remaining stable in severity from that point onward. Some people have reported brief periods of remission, however this is very rare and the symptoms usually return.
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 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. Stress does not cause SD, but it can worsen the spasms.
SD is generally catergorized into two primary forms: adductor spasmodic dysphonia (AdSD) and abductor spasmodic dysphonia (AbSD). Adductor SD, the most common form, affects approximately 80–90% of people with SD. In this type, spasms, usually in the thyroarytenoid muscle (TA), force the vocal folds together in adduction, or closing. AdSD may also affect the lateral cricoarytenoid muscle (LCA) or interarytenoid (IA). These 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."
If the voice cuts out, or breaks when the voiced sound is at the beginning of the word, as in “eels,” the speaker often strains over the spasm to get the word started. If the troubling vowel occurs in the middle of the word, the voice often breaks the word in two.
For example, the word “lawn” would come out as “la---awn.” When the voiced vowel is at the end of the word, such as “pleasingly,” the word terminates earlier than it should, causing the speaker to sound as if he or she is swallowing words. The speaker usually has no effort or disruption with the non-voiced vowels and unvoiced consonants. However, since most words and sentences contain voiced sounds, an adductor voice can be very hard to understand as the spasms continuously interrupt the flow of speech.
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 AdSD often complain of having to struggle to speak.
Abductor spasmodic dysphonia. AbSD, a less common form, occurs in approximately 10–20 percent of cases and results from spasms when the posterior cricoarytenoid muscles (PCA) abducts, or opens, the vocal folds. AbSD causes problems with the production of “voiceless” speech sounds, which normally sound “airy” or “breathy” when produced.
Examples of “voiceless” speech sounds are: “f” as in funny, “k” as in kite or cat, “t” as in top
“h” as in hello, “th” as in thank you, and “s” as in master.
In AbSD, the spasms in the abductor muscles cause the vocal folds to remain open for a longer duration than should normally occur on these sound combinations. This results in the voice taking longer to complete the voiceless sounds, which makes the speaker sound “breathy.” For example, a person with AbSD might produce the word “he” as “h……….he.” The symptoms of AbSD can occur on any voiceless sound at the beginning, middle, or end of the word.
As with AdSD, the symptoms in AbSD 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 AbSD expend too much air as they produce sound, they often describe feeling winded or out-of-breath during speaking.
Subtypes of spasmodic dysphonia. While most people with spasmodic dysphonia fall into these two categories, researchers have identified several subtypes. A person may have a mixed form with symptoms of both AdSD and AbSD. Some people with SD also have a tremor in their voice. Typically, tremor affects muscle groups outside of the larynx and can cause the voice to sound “shaky” or “quivery.” Like adductor and abductor spasmodic dysphonia, the symptoms of vocal tremor can range from mild (infrequent, periodic tremor) to severe (affecting all voicing and singing). A very severe tremor with significant shaking can even cause the voice to cut out, sounding similar to the voice breaks in AdSD. In addition, sometimes treatment of the SD symptoms reveals a co-existing underlying tremor.
Muscle tension dysphonia. SD may also be accompanied by or misdiagnosed as muscle tension dysphonia (MTD), which is sometimes also referred to as a “hyperfunctional” voice. Although the MTD voice sounds tight or strained and sometimes similar to AdSD, MTD is considered a functional condition rather than a neurological one. MTD occurs when the speaker exerts too much pressure or effort on the laryngeal muscles. In some cases, people with AdSD may try to hold their vocal folds tighter in an attempt to control them. This compensatory mechanism can result in the person developing a variant of MTD on top of the SD.
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.
What makes finding the cause even more difficult is that the spasms do not occur in all types of speech. Two studies conducted in 1968 by Aronson, et. al., and one conducted by Ludlow and Connor in 1987, have shown that the symptoms of SD improve or disappear during laughing, crying, yelling, throat clearing, coughing, whispering, and humming.\Generally, SD does not affect the emotional aspects of speech. As described earlier, SD is task-specific and tends to affect only normal conversational speech. Researchers consistently have identified abnormalities in brainstem reflexes and other aspects of disordered neurological function in people with spasmodic dysphonia.
Genetic factors may put some people at greater risk of developing spasmodic dysphonia, particularly those who have family members with any form of dystonia.
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. Regardless of the cause, it is most important to make a correct diagnosis and then consider the available treatment options.
Spasmodic dysphonia can be difficult to diagnose because the anatomy of the larynx is normal. SD has no objective pathology that is evident through x-rays or imaging studies like a CT or MRI scan, nor can a blood test reveal any particular fault. In addition, several other voice disorders may mimic or sound similar to it. The excessive strain and misuse of muscle tension dysphonia (MTD), the harsh strained voice of certain neurological conditions, the weak voice symptoms of Parkinson’s disease, certain psychogenic voice problems, acid reflux, or voice tremor are often confused with SD. Therefore, the best way to diagnose the problem is to find an experienced clinician with a good ear.
Who treats spasmodic dysphonia? Usually an otolaryngologist, a physician that specializes in diseases of the ears, nose, and throat (ENT), diagnoses SD. Some otolaryngologists, called laryngologists, have additional postgraduate training and specialize in voice disorders. Many otolaryngologists work with a speech pathologist, a clinician who has expertise in the evaluation and non-medical treatment of voice disorders. A neurologist may also be part of the diagnostic team to evaluate a patient for other forms of dystonia or other neurological conditions.
After taking the medical history, the physician and speech pathologist listen carefully to the person’s speech to subjectively identify specific signs of SD, such as voice breaks. To help differentiate the condition and subtype, they ask the patient to read and speak specific sentences loaded with certain sounds. While additional evaluations may help to support or refute the conclusion, the experienced clinician’s expert perceptual analysis usually serves as the basis for making the SD diagnosis.
The physical examination continues by looking at the larynx in action. Even though the person with SD often has normal anatomy, the physician should look at the larynx to rule out other common laryngeal disorders that can result in a hoarse voice. These include conditions such as vocal nodules or chronic laryngitis.
One way to view the larynx is to insert a rigid endoscope, a straight, narrow metal rod containing a camera, through the mouth and toward the back of the throat while the person is saying “eeeee.” In this manner, the otolaryngologist can obtain a close-up view of the structures of the larynx and the movement of the vocal folds. Another approach to viewing the vocal folds involves the use of a flexible endoscope. In this method, a very narrow, flexible tube is inserted through one nostril and down through the throat, which allows the doctor to evaluate the movements of the larynx while the person is speaking or singing. Often, these endoscopic examinations are performed with a specialized flickering light called a stroboscope which allows the clinician to further evaluate the rapid fine movement of the vocal folds.
The otolaryngologist may recommend a laryngeal electro-myography (EMG) test to obtain specific information about the muscles involved. EMG involves inserting a thin needle electrode through the neck into the muscles of the larynx and evaluating the electrical activity of the muscles at rest and during speaking. With a confirmed diagnosis, the doctor and patient can find an appropriate course of treatment.
To date, no known cure for spasmodic dysphonia exists. However, several forms of treatment are available to alleviate or control the symptoms of the vocal spasms on a temporary or long-lasting basis. While these do not address the underlying neurological dysfunction, they usually give enough symptom relief to enable a person to regain control of and improve the quality of their voice.
Similar to other problems affecting the larynx, SD can be approached with a single type or a combination of treatments, as no single strategy will be appropriate for every case. A physician’s recommendation of a specific treatment regimen depends on his or her experience and expertise in diagnosis and treatment of voice disorders, as well as the collaborative input of the patient. In general, treatment for voice disorders falls into three broad categories: speech therapy, medical therapy, and surgery. Perseverance and patience are important when dealing with SD, and finding the best treatment for each individual involves time and a team effort with the patient and the specialists
Please note: The treatment options for spasmodic dysphonia featured on the NSDA website are reviewed by the NSDA Medical Advisory Board. The criteria for inclusion of specific treatments are based on whether treatment protocols have been verified by publication of peer-reviewed research, and/or whether they have been endorsed via the general consensus of experts from the fields of neurology, otolaryngology, and speech-language pathology.
Oral medications. Oral medications provide little relief from the symptoms of spasmodic dysphonia. However, if other forms of dystonia are present, medications may help relieve those related symptoms. At this time, no medication is specifically indicated to treat a dystonia; however, a number of products, including Sinemet® (carbidopa/levodopa), Ativan® (lorazepam), Klonopin® (clonazepam), Neurontin® (gabapentin), and Valium® (diazepam), are used to settle muscles or nerves with excess activity. Other categories of medications used in the treatment of dystonia include anticholinergics, benzodiazepines, and baclofen.
Some patients have reported a benefit from these, but often this can be at the expense of common side effects such as drowsiness or nausea.
Botulinum toxin. Botulinum toxin (BTX) is derived from the bacterium Clostridium botulinum. It is a nerve “blocker” that binds to the nerves that lead to the muscle and prevents the release of acetylcholine, a neurotransmitter that activates muscle contractions.
In spasmodic dysphonia, laryngeal muscles spasm because too many or the wrong type of signals travel from the brain through the nerves to the muscles. BTX is a biologic product and is injected directly into the affected muscles. It blocks these nerve signals, reducing the number and severity of the spasms.
Since 1984, BTX has been used to treat the symptoms of thousands of people with SD and its efficacy and safety have been documented in numerous medical publications. Furthermore, the American Academy of Otolaryngology & Head and Neck Surgery has documented the use of BTX for SD in a policy statement. Its use by physicians to treat SD is considered “off-label” by the FDA. However many other medicines are used successfully off-label for a number of conditions and this designation does not limit a physician’s use of a medicine.
BTX exists in a number of forms, but only types A and B are available commercially. They are administered similarly but have different dosing, onset of action, and length of activity. The majority of people with SD receive BTX type A; therefore, the remainder of this discussion focuses on this type.
Surgery. Surgical procedures have been used to treat SD for more than thirty years. The majority of the operations are designed for patients with adductor spasmodic dysphonia (AdSD) and few surgical options exist for abductor spasmodic dysphonia (AbSD). This section only discusses operations designed to treat AdSD. The goal of these procedures is similar to that for botulinum toxin: weaken the muscles that are closing too tightly in order to produce a relaxed and fluent voice. This can be accomplished in two distinct ways.
The first involves adjusting the laryngeal supports to physically separate the vocal folds. The second involves adjusting the nerve input or muscle tension by physically altering the muscles or nerves going to the larynx.
Speech therapy. Speech therapy offered by a speech language pathologist (SLP) involves training the person to alter voicing techniques. For instance, the speech therapist may point out that the patient is producing his or her voice with poor breath support or poor tongue placement in the mouth. Through exercises and practice, the patient can gain better insight into how to speak more efficiently and effectively.
Unfortunately, this approach often produces incremental benefit for the typical SD patient since SD is a neurologic condition over which the patient has little or no control. While some have suggested that SD can be cured through speech therapy, few practitioners or patients have had this experience. Speech therapy is generally seen as a possibly helpful adjunct to other therapies such as botulinum toxin (BTX) injection and to help SD patients who have excess voice strain to “unload” some vocal muscle tension.
Some people with spasmodic dysphonia benefit from the use of a voice amplifier for the phone or that of a self-contained microphone used in conjunction with any FM radio.
Understanding what causes the SD patient's voice to be better or worse is an important step in managing symptoms of SD.
What often helps make voice quality better?
• Vocal exercise (humming, speaking slowly, reciting nursery rhymes)
• Volume control (talking softly or loudly)
• Feeling relaxed
• Breathing deeper breaths, exhaling before speaking, not holding onto the breath
• Environmental control (talking one-on-one, not being interrupted)
• Using voice early in the morning
• Sensory gestures (neck muscle massage, covering eyes, pinching nose)
• Physical exercise
• Mental aspects ("not thinking about it", keeping a good attitude)
• Miscellaneous (physical rest, vocal rest, warm liquids, laughing)
What often makes voice quality worse?
• Stress (being tense, being in a hurry)
• Speaking on the telephone
• Speaking in a loud or large space
• Trying to talk over noise
• Lack of sleep
• Negative thinking
• Miscellaneous (overuse, weather changes, having a cold)
Support groups for spasmodic dysphonia
For online and area support groups, please visit the Patient Support area of the National Spasmodic Dystonia Association.
This information was developed by the National Spasmodic Dystonia Association and is herewith used with permission.
National Spasmodic Dystonia Association. What is Spasmodic Dysphonia? Available at: https://www.dysphonia.org/spasmodic-dysphonia.php. Last accessed February 3, 2014.
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