Successful treatment of selected cases of abductor spasmodic dysphonia using botulinum toxin injection

Ten patients with abductor spasmodic dysphonia, who exhibited spasmodic bursts and heightened activity of the cricothyroid muscle during speech, were selected for participation. Between 5 and 20 U of botulinum toxin type A were injected into both right and left cricothyroid muscles. Six patients benefited substantially, whereas four did not. Acoustic analyses of voice patterns showed similar changes to the clinical impressions. Significant group improvements were found in sentence duration while selected patients improved in the proportion of their speech that was voiced and the duration of their voiceless consonants. Those patients with abductor spasmodic dysphonia and other muscle abnormalities in addition to the cricothyroid and with constant breathiness did not benefit.