OBJECTIVE:

Objective evaluation of botulinum toxin A (BTX-A) dosing by determination of the statistical relationship between injection amount and duration of side effects and normal voice in adductor spasmodic dysphonia (SD) patients. From this information, to provide a rational guide to determine the initial and follow-up BTX-A amounts for injection.

STUDY DESIGN AND SETTING:

Private laryngology clinic. Statistical analysis was performed on data obtained from 101 patients with SD.

RESULTS:

Significant and predictable positive correlations were found between duration of side effects and duration of normal voice after BTX-A injection in patients with SD. Dose of BTX-A injected also appeared to have a significant positive correlation with duration of side effects, but a negative correlation with duration of normal voice. A trend toward more severe side effects was seen with larger doses of BTX-A injections.

CONCLUSIONS AND SIGNIFICANCE:

Increased understanding of the response of the human voice over time after BTX-A injection at various doses suggests new ideas to further increase clinical efficacy with the use of lower BTX-A doses.