Objective: Botulinum toxin (BT) injection improves objective and subjective voice measurements in spasmodic dysphonia; however, it is not clear whether the results are entirely caused by the neuromuscular blocking effects of BT or whether other factors (e.g., psychological or emotional) play a part. The aim of this study is to investigate whether nonpharmacologic factors contribute to the changes observed in the quality of life (QoL) after BT treatment of spasmodic dysphonia.
Study design: Prospective cohort study.
Methods: Thirty-eight consecutive spasmodic dysphonic patients attending for repeat BT injections were investigated by recording their Voice Handicap Index (VHI) scores at three time points: 1) immediately prior to injection (baseline), 2) 1 day postinjection (when least pharmacologic change is expected), and 3) 2 weeks postinjection (when most pharmacologic change is expected). The changes in the total and domain VHI scores were compared between the two postinjection scores and the baseline value using two-way analysis of variance and the post hoc Bonferroni test.
Results: Most of the change in VHI score occurred between the baseline and first postinjection measurement. For two of the domains (total and emotional), the change was statistically significant. The change between the two postinjection assessments was minimal, and no domain showed statistically significant change.
Conclusions: Our data indicate that the early improvements in QoL after BT injection can only in small part be attributed to the neurotoxic effects of the agent. We cannot say whether the reported effects in our study are attributable to a strong placebo response or are a real consequence of the patient's changing emotional state.