Differences in Botulinum Toxin Dosing Between Patients With Adductor Spasmodic Dysphonia and Essential Voice Tremor

Objectives. To explore possible dose differences in average botulinum toxin (BTX) given to patients with adductor spasmodic dysphonia (ADSD) compared with patients with essential voice tremor (EVT). Methods. A retrospective study compared the average BTX dose injected in equal doses to the thyroarytenoid (TA) muscles of 51 patients with ADSD with 52 patients with EVT. Results. Those with ADSD received significantly higher total doses (6.80 +/- 2.79 units) compared with those with EVT (5.02 +/- 1.65 units). Dose at time of first injection, age at time of first injection, gender, year of first injection, and average time between injections were included in multivariate analysis but did not interact with total average dose findings. Conclusions. Patients with ADSD may need relatively higher doses of BTX injections to bilateral TA muscles compared with patients with EVT.