Spasmodic Dysphonia (SD): Definition and Treatments

Spasmodic Dysphonia is a non-life-threatening neurological disorder in which the muscles of the larynx involuntarily spasm and interfere with the voice.

Spasmodic dysphonia (SD) is a focal dystonia, in this case involving the larynx—i.e., laryngeal dystonia. Laryngeal dystonia typically affects the voice, but can occasionally also affect breathing (respiratory dystonia). The term spasmodic dysphonia refers specifically to voice-affecting laryngeal dystonia.

Adductor vs. Abductor SD

There are two main variants of SD. In the first variant, adductor SD (AD-SD), the vocal cords are pressed together excessively, intermittently cutting off words or giving the voice a constant strangled quality; this variant comprises 90% of the cases of SD.

In the second variant, abductor SD (AB-SD), the vocal cords are abruptly and momentarily pulled apart while talking, causing the voice to drop out completely or down to a whispery, breathy sound. There are some cases in which a person has both of these variants: this is called mixed AB-AD SD.

Classic vs. Tonic SD

Another distinction that can be made is between classic variant and tonic variant cases of SD. In classic variant SD, the spasms cause phonatory arrests—that is, while the person is speaking, intermittent words or syllables are choked off (with AD-SD) or drop out (with AB-SD).

In tonic variant SD, the spasms are more continuously sustained, so that the voice continuously sounds either strained (with AD-SD) or breathy (with AB-SD), but without any actual phonatory arrests. Because the presence of phonatory arrests is the symptom most often associated with SD, tonic variant SD goes undiagnosed or misdiagnosed far more frequently than does classic variant SD.

Treatments for Spasmodic Dysphonia

Botox Injections

There is no definitive “cure” for SD, but for most patients, periodic injections of Botox™ into the muscles of the larynx help a great deal, if there is optimal dosage and placement. These injections relax the malfunctioning muscles of the larynx, thereby minimizing the spasms and their impact on the voice.

The effect of an injection typically lasts a few months, and then another injection is needed. For those having difficulty getting good results with Botox™ therapy, see our video below “Spasmodic Dysphonia: When Botox Disappoints.”

What can I expect from Botox injections?

  1. The initial two or three injections may be needed to establish optimal dose, since there is no way to predict the best dose; instead, these initial injections provide that understanding.
  2. After each injection, it takes between one and five days, typically, for the Botox effect to be complete.
  3. If you have AD-SD, we expect transient initial weakness to be a side effect, but your voice should still be functional other than in noisy environments during these initial days. If you have AB-SD, the initial side effect might be mild breathing noises when you exert yourself.
  4. The golden period of voice quality should last between 8 and 16 weeks on average before another injection is needed. Most people, therefore, receive between 3 and 5 injections per year, and the interval is determined not only by dose, but by individual “biology.”

SLAD-R Surgery

The leading surgical treatment currently offered for SD, Selective Laryngeal Adductor Denervation-Reinnervation (SLAD-R), can be an option for individuals with the AD-SD variant. However, no treatment for SD works satisfactorily for all. The history of each of the several surgical treatments for SD always includes some failures.

Speech Therapy

Speech therapy is another treatment sometimes suggested for SD. While there are strong and even passionate individual proponents of speech therapy, the consensus view is that speech therapy is not expected to substantially improve the voice’s capabilities or reduce spasms other than perhaps in the therapy room1.

A brief course of speech therapy can be very helpful for patient education and perhaps a search for sensory tricks. Much confusion surrounds this subject, because individuals who have a nonorganic voice disorder can be mistakenly diagnosed with SD, and nonorganic voice disorders are routinely “cured” with speech therapy alone.


Adductory Spasmodic Dysphonia

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AD-SD (1 of 2)

Sustained, clear phonation, standard light. Note vibratory blur of the vocal cord margins. The false vocal cords (lines) are in normal relation to the true vocal cords.

AD-SD (2 of 2)

Involuntary adductory spasm. Note that the false vocal cords suddenly over-close (arrows) as a result of the adductory spasm, and voice momentarily stops (along with vibratory blur).

Abductory Spasmodic Dysphonia

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AB-SD (1 of 4)

Prephonatory instant, with arytenoid cartilages involuntarily positioned apart. Mostly tonic position giving voice relatively constant breathiness.

AB-SD (2 of 4)

Phonatory blur, standard light. Again note the separation of the arytenoid cartilages posteriorly (upper end of the photo), and broad vibratory blur, both consistent with breathy voice.

AB-SD (3 of 4)

Occasionally, patient is able to bring posterior cords together for an instant of normal-sounding voice.

AB-SD (4 of 4)

An instant later, the vocal cords involuntarily separate due to an abductory spasm, dropping the voice again to a whispery quality.

Abductor Spasms, Worsened by Cognitive Loading

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Abductor spasmodic dysphonia patient (1 of 4)

Vocal cords in normal breathing position, in a person with abductor spasmodic dysphonia (SD). The next three photos show how the vocal cord spasms seen with SD can get worse when the person performs more cognitively loaded or involved tasks (that is, the person has to think more). This pattern is related to the widespread understanding that SD’s symptoms can be task-specific.

Limited abductor spasms (2 of 4)

When making voice with guttural vocal fry or sustained creaky falsetto, this person is able to keep the vocal cords together, at least part of the time.

Increased abductor spasms (3 of 4)

When the person tries to sustain a sung tone (slightly more cognitively loaded), the vocal cords involuntarily separate, producing a very breathy voice.

Even greater abductor spasms (4 of 4)

When the person speaks (even more cognitively loaded), the vocal cords separate even further, and the voice’s breathiness is pronounced.

Adductory Spasm

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Adductory spasm (1 of 2)

Continuous phonation, standard light. Note the position of the false cords in relation to each other, and also the distance between the anterior face of the arytenoids and the petiole of the epiglottis.

Adductory spasm (2 of 2)

A moment later, an adductory spasm occurs. The spasm may momentarily stop the voice (phonatory arrest). Note the inward squeezing of the entire supraglottis (false cords, arytenoids, and petiole).

Laryngology 401: PCA-only Paresis, but the Actual Voice Problem Is Spasmodic Dysphonia

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Sense of instability (1 of 3)

This person had a major voice change after thyroidectomy for a large goiter. Within 2 months, voice recovered fully–except for a sense of instability. The PCA-only paresis is not the explanation because voice-making muscles (TA + LCA) are intact. And in fact vocal capability testing shows that both yell and projected voice are normal. The visual finding here of vocal cord bowing and capacious ventricle do not count as a breathing position finding with PCA-only paresis due to the unopposed action of LCA muscle, combined with an uncontracted TA muscle, both of which cause pseudo-bowing.

Vibratory amplitude (2 of 3)

During phonation under strobe light, with TA tensing, “bowing” disappears. Furthermore the vibratory “blur” at the margin of the left fold (right of photo) is equal to the right (left of photo), telling us that vibratory amplitude is approximately the same on both sides.

Spasm (3 of 3)

An audible/ visible spasm occurs when the right vocal cord jerks laterally for 4 frames (~ 1/8th of a second). The problem isn’t PCA weakness on the left (right of photo), but instead an abductory spasm on the right (left of photo), fully mobile cord!

Remarkable Task-Specificity of Spasmodic Dysphonia

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Young singer (1 of 4)

This young soprano has had to put singing to the side due to a peculiar instability at a very specific part of her singing range: approximately G4 to B4. Speaking voice is completely normal. Above and below G4 to B4 the voice works well. Here, during somewhat distant view during breathing, no mucosal abnormality is seen.

Phonation (2 of 4)

During phonation at high pitch designed to reveal margin swelling, there is a slight gap of “physiologic bowing” but arytenoids seem to approximate well.

Closed phase (3 of 4)

Closed phase of vibration at G4 (392 Hz). Nothing significant is seen in this admittedly somewhat distant view.

Sudden spasm (4 of 4)

Ten frames, a fraction of a second-later, a sudden spasm is seen (arrows) and heard. This adductory spasm happens consistently and repeatedly with numerous elicitations, but only in the narrow pitch range already noted in caption 1.

Assessment of Vocal Phenomenology Protects from Visual Red Herrings

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Swelling? (1 of 2)

The vocal cords of a physical education teacher with mild, intermittent ‘hoarseness’ and cracking of voice. Given her occupation, the mind goes to “voice abuse” and the margin swelling seen here might play into the diagnosis of “vocal overdoer with mucosal injury.” However, the vocal capability battery (voice testing) protects from a misdiagnosis.

Spasmodic dysphonia (2 of 2)

During the vocal capability testing (part 2 of the Integrative Diagnostic Model), one hears no significant mucosal swelling phenomenology (during application of vocal cord swelling checks), but instead a quivery, jittery instability. The actual diagnosis? Spasmodic dysphonia.

Table of Contents

Do medications work in treating SD?

Medications are not typically highly useful in persons with focal dystonia. We think that all three of these options—speech therapy, surgery, and medication—are on the table.

Yet we continue to see a fourth option as the standard of care for now: periodic Botox injections into the tiny muscles of the larynx (voice box).

Not when the diagnosis is clearly SD. Even when the voice problem is clearly established to be SD—that is, neurological—it is understandable that some patients continue to believe their problem is psychological, because the voice change came after a major stressful life event.

Others notice that symptoms are worse when they are stressed or fatigued. They may also note some reduction of symptoms when under the influence of alcohol or a tranquilizer such as valium. Despite these legitimate observations, it is important to remember that the disorder is neurological and not psychological.

Why, then, do the “psychological” effects just mentioned occur? Because though the disorder is neurological, symptoms may be made worse by stress, in the same way that high blood pressure or other disorders may be made worse by stress, too.

Peak incidence is probably in 50’s and 60’s but can begin in twenties, and I have a few patients under twenty. Gravelly voice of being older is different from this disorder, which includes squeezing, strained quality along with “catches” or lost syllables—or drop-outs to a brief moments of whispering.

Some public persons (who have acknowledged their SD) include Diane Rehm of NPR, Robert Kennedy, Jr, and Scott Adams of Dilbert fame.

Once SD is established and obvious, it is not common to develop highly noticeable dystonia in other than laryngeal muscles. Occasionally, however, it does happenHandwriting might manifest limb dystonia, for example. 

  1. There may be a long unsuccessful search for diagnosis. The range in our practice is a few weeks to 30 years. The reason for delay is the relative rarity of the disorder, explaining physician unfamiliarity with the diagnosis.
  2. Patients may have been told (erroneously) that the disorder is psychological.
  3. Symptoms often vary inexplicably. Persons with SD may notice “good” days and “bad” days, or even “good” moments and “bad” moments. Some experience a lot of variability; others relatively less. Some with a lot of variability attempt to find a dietary, stress-related, or other cause of this variability. To their detriment, patients may have been encouraged to “take responsibility” for this variability when it is much better to understand that variability is simply a known component of the neurological disorder itself.
  4. Patients may notice that certain words or sounds are especially difficult to say.  For example, words beginning with “h” or with a vowel sound are often mentioned. Some persons find their names or phone numbers are hard to say.
  5. The telephone, drive-up windows, automated phone attendants pose special difficulty. Virtually everyone with SD says, “I hate the telephone!”

Keep in mind that MTD and SD are not the same thing. There is a variant of SD that causes strain only (tonic variant SD). In this variant, there are no phonatory arrests (stoppages, catches). 

MTD is instead a functional problem that can be treated with very expert therapy. There aren’t many true “experts” on addressing this. Tonic variant SD is a neurological disorder for which Botox is highly effective. Sadly, while Botox can dramatically lessen the symptoms especially in the speaking voice, it cannot return a premier singing voice.

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Spasmodic Dysphonia:
A Peculiar Voice Disorder

Dr. Robert Bastian reviews the various types and subtypes of spasmodic dysphonia (SD). Numerous voice examples are included, along with video of the vocal folds.

SD is a rare neurological disorder caused by laryngeal dystonia, and it interferes with the smooth functioning of the voice. Tiny spasms of the vocal folds may cause the voice to catch or cut out, strain or squeeze away, and sometimes to drop momentarily to a whisper.

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Spasmodic Dysphonia: When Botox Disappoints

In this video, Dr. Bastian discusses common problems with Botox treatment for spasmodic dysphonia (SD) and offers clear, practical advice to increase the effectiveness of these treatments.

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Is my Vocal Weakness from Spasmodic Dysphonia Spasms, or a Botox Side Effect?

Persons with Spasmodic Dysphonia (SD) may describe the one of the effects of that disorder as vocal “weakness.” After treatment with Botox, they may use the same word—“weakness”—to describe one of the early side effects of treatment with Botox. Especially after the initial several injections, before they have become treatment “veterans,” some patients struggle to distinguish between these two kinds of vocal “weakness.”

As a result they may have difficulty communicating whether the next Botox injection should be a higher or lower dose. In an attempt to address this problem, this video compares and contrasts the vocal weakness of SD with the (initial) post-injection Botox-related vocal weakness.

Dr. Bastian explaining a Videoendoscopic swallowing study
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2014 NSDA 25th Anniversary Symposium

In this video, Dr. Bastian leads a panel discussion on Spasmodic Dysphonia.

RFK Jr YT Thumbnail
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Why Does Robert Kennedy Jr. Have a Hoarse Voice? The Answer Is SD…

Voice Disorders caused by Spasmodic Dysphonia
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A Tour of Voice Disorders with a Focus on Spasmodic Dysphonia

In this webinar, Dr. Robert W. Bastian provides an overview of the anatomy of the voice and then touches on different types of voice disorders with a focus on spasmodic dysphonia (laryngeal dysphonia).
  1. Ludlow CL. Treatment for spasmodic dysphonia: limitations of current approaches. Curr Opin Otolaryngol Head Neck Surg. 2009; 17(3): 160–165. []
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