Spasmodic dysphonia (SD) is a neurological voice disorder caused by involuntary spasms of the laryngeal muscles during speech. It is a form of focal dystonia — like writer’s cramp, but in the larynx. It is not psychological, not a result of voice misuse, and not curable — but it is highly manageable with regular botulinum toxin injections.
Types of Spasmodic Dysphonia
Adductor Spasmodic Dysphonia (AdSD)
By far the most common form (approximately 90% of cases). Involuntary spasms of the adductor muscles (particularly the thyroarytenoid and lateral cricoarytenoid) cause the vocal folds to close too forcefully during speech. The voice sounds strained, strangled, or squeezed — as if someone is grabbing the throat from the inside. Speech may cut in and out, with intermittent moments of normal voice followed by tight, effortful spasms. The disorder is task-specific: whispering is often easier than normal speech, and singing may be preserved.
Abductor Spasmodic Dysphonia (AbSD)
A much rarer form in which spasms of the posterior cricoarytenoid (the only abductor muscle) cause the vocal folds to be pulled apart during voiced sounds. The voice has intermittent breathy breaks — particularly on voiceless consonants followed by vowels (words beginning with ‘h’, or phrases like ‘hold on’). It can be confused with muscle tension dysphonia but has a distinct neurological character.
What Causes Spasmodic Dysphonia?
SD is a disorder of the basal ganglia — the same brain circuitry affected in Parkinson’s disease and other movement disorders. The laryngeal muscles receive abnormal signals that trigger involuntary contractions during the specific motor task of voiced speech. Onset is typically in middle age, more common in women, and often begins after a period of stress, illness, or heavy voice use — though these are triggers, not causes.
Diagnosis
Diagnosis requires careful laryngoscopy during connected speech — not during isolated vowel sounds. The spasms are often invisible at rest and apparent only during running speech tasks. A trained laryngologist or neurolaryngologist can usually make the diagnosis confidently on clinical grounds.
Botulinum Toxin Injection
Injection of botulinum toxin (Botox) into the thyroarytenoid muscles is the standard of care for adductor SD. A small, precisely placed injection weakens the muscle just enough to prevent spasms without eliminating voice entirely. The effect lasts approximately three to four months, after which the injection is repeated.
The Art of an Injection
Achieving the optimal injection — enough to reduce spasms but not enough to produce significant breathiness — requires considerable experience. The dose and placement are individualized; most experienced injectors have developed a highly personalized approach for each patient. Results typically improve over the first several injection cycles as the dose is refined.
Other Treatments
Voice Therapy
Voice therapy alone does not treat the dystonia, but it can help patients optimize their voice between injection cycles and manage compensatory muscle tension that adds to the dysphonia.
Surgical Options
Selective laryngeal adductor denervation-reinnervation (SLAD-R) is a surgical procedure that permanently denervates the thyroarytenoid muscles and reinnervates them with a non-spasming nerve. It offers durable results in carefully selected patients but is performed at only a handful of specialized centers worldwide.
Living with Spasmodic Dysphonia
SD is a chronic condition that requires ongoing management. Most patients achieve excellent functional voice with regular botulinum toxin injections and can lead fully active professional and personal lives. Support organizations such as the National Spasmodic Dysphonia Association (NSDA) provide education and community for affected individuals.