Botulinum Toxin Dosing Trends in Spasmodic Dysphonia Over a 20-year Period

Area of Science:

• Neurology
• Otolaryngology
• Pharmacology

Background:

• Adductor spasmodic dysphonia (ADSD) is a chronic neurological voice disorder.
• Botulinum toxin (BTX) injections are a primary treatment for ADSD.
• Understanding long-term BTX dosing patterns is crucial for optimizing patient management.

Purpose of the Study:

• To identify botulinum toxin (BTX) dosing trends in patients with adductor spasmodic dysphonia (ADSD) receiving at least 20 injections.
• To describe distinct BTX dosing patterns: 'classic' (decrease then stabilize) and 'fluctuating'.
• To compare age and dosing intervals between patients with classic and fluctuating BTX dosing trends.

Main Methods:

• Retrospective case series of 49 patients with ADSD who received ≥20 BTX injections.
• Analysis of BTX dose and interval between injections from 1993-2013.
• Comparison of age at initial injection and dosing intervals between identified dosing groups.

Main Results:

• A significant decrease in BTX dose was observed during the first 10-15 injections.
• Patients with a 'fluctuating' dosing pattern had significantly shorter injection intervals (97 days) compared to the 'classic' pattern (137 days).
• No significant difference in mean age at initial dose was found between the two groups.

Conclusions:

• The average botulinum toxin (BTX) dose for adductor spasmodic dysphonia (ADSD) decreases initially and then stabilizes with long-term treatment.
• A 'fluctuating' BTX dosing pattern is associated with shorter injection intervals compared to a 'classic' pattern.