Tremor Makes a Difference: A Comparative Study of the Demographics and Treatment Outcomes in Patients With Adductor Spasmodic Dysphonia With or Without Vocal Tremor

Objectives: This study aims to evaluate the demographic differences between those with adductor spasmodic dysphonia with vocal tremor (AdSD(+)VT) and those without vocal tremor (AdSD(-)VT) and to analyze their response to treatment with botulinum neurotoxin (BoNT-A). Study design: Retrospective cohort study. Methods: A database review of all spasmodic dysphonia patients treated with BoNT from 1989 to 2018 at the Mayo Clinic in Arizona was performed. Only patients who had received ≥4 injections of BoNT-A for AdSD were included. Patients were divided into two cohorts: those with coexistent vocal tremor (AdSD(+)VT) and those without vocal tremor (AdSD(-)VT). Results: The final analysis included 398 patients, with 210 AdSD(+)VT patients (53%) and 188 AdSD(-)VT patients (47%). The length of follow-up and median number of treatments were similar between cohorts. AdSD(+)VT patients were more likely to be female (P < 0.001), and older at onset (P < 0.001) and first injection (P < 0.001). The mean maximal benefit was significantly lower for the AdSD(+)VT cohort (P < 0.01), however the mean length of benefit was similar (P = 0.70). Conclusions: Demographic differences exist between AdSD(+)VT and AdSD(-)VT patients. AdSD(+)VT patients benefit from BoNT-A treatment; however, our analysis suggests that the degree of their maximal benefit is less than in those without VT.