Abstract
The symptoms of adductor spasmodic dysphonia (SD) include uncontrolled voice breaks during vowels in sentences, intermittent hoarseness and a slower than normal speech rate. Each of these symptoms is improved following botulinum toxin injections into selected laryngeal muscles.1–3 Similarly, in oral mandibular dystonia, patients’ sentence and word durations are increased relative to normal prior to treatment,4 demonstrating a slow speech rate. Following botulinum toxin injections into selected lingual and/or mandibular muscles, the word and sentence durations become reduced to within the normal range.4 Both studies, then, suggest that botulinum toxin injections improved the speed of speech movements in patients following treatment. Both disorders are thought to be due to abnormalities of muscle tone. In spasmodic dysphonia, for example, spasmodic bursts in the thyroarytenoid muscles, contained in the vocal folds, are associated with interruptions in speech.5 Because botulinum toxin impairs neuromuscular transmission producing a muscle weakness, these improvements in speech and voice function were thought to be due to reduced spasm amplitude in the injected muscles.
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