Spasmodic Dysphonia: A 20-Year Experience of Injecting Botulinum Toxin

Objectives: (1) Report the initial dosing for adductor and abductor spasmodic dysphonia (ADSD, ABSD). (2) Identify trends in dosing for patients with SD over extended time. Methods: A retrospective review of the medical records of 149 patients who received 2484 Botox injections from the same physician at a tertiary medical center between January 1993 and December 2012. The location and dose of injection, age of the patient at injection, and the interval in days between injections were recorded. Results: There were 13 ABSD patients and 136 ADSD patients. The initial dose injected into each vocal fold for patients with ABSD (mean = 2.8 units) was significantly higher than for patients with ADSD (mean = 1.52; t = 4.46; P < .001). Seventy patients received 10 or more injections during the study period (range, 1-92 injections). Sixty-six patients have been followed for greater than 5 years. There appear to be several trends which determine the proper dose for management of vocal cord spasms. One group establishes a stable dose with minimal side effects and adequate interval of normal phonation. A second group tends to have variability in the tolerance of side effects and voice results from each injection and requires dose modification continually over time. Conclusions: Analysis of this patient cohort receiving a high number of injections over an extended period of time reveals variable dosing patterns. This may represent subjective differences in patients’ ability to tolerate side effects of Botox treatment. It may also indicate variability in the etiology and pattern of this neurologic disease.