An analysis of the efficacy of botulinum neurotoxin type a in treating cervical dystonia.

[BACKGROUND] The first-line treatment for cervical dystonia (CD) consists of repeated intramuscular injections of botulinum toxin (BoNT). However, the efficacy in some patients may be unsatisfactory and they may discontinue treatment.

[OBJECTIVE] To examine the factors associated with the maximum rate of remission in patients with CD after initial botulinum neurotoxin type A (or botulinum toxin type A abbreviated as BTX-A or BoNT-A) treatment.

[METHODS] Patients with CD who received BoNT-A injections were evaluated using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and the Tsui scale, with follow-up endpoints lasting until the start of the second injection. Patients who did not receive a second injection of BoNT-A were followed up for at least 5 months. The maximum remission rates were determined using the lowest Tsui and TWSTRS total scores during the follow-up period. We obtained basic information about these patients such as age, gender, duration of disease, presence of additional disease, types of torticollis, presence of anxiety, depression, tremors, single-photon emission computed tomography (SPECT) findings, injected dose, and so on from their medical records.

[RESULTS] A total of 70 patients with CD participated in this study, with males comprising 35.7% (25 individuals) with an average age of 45 ± 14 years old. The duration of disease was an independent risk factor for determining whether a complete remission has been attained using the Tsui scale (odds ratio [OR] = 0.978, 95% confidence interval [CI]: 0.959-0.997, P= 0.026). The optimal cut-off point for predicting patients who were unable to achieve complete remission based on duration of disease was 7.5 months (AUG = 0.711). Patients with CD with additional disease had greater difficulty achieving complete remission than those with CD alone based on TWSTRS assessments (P= 0.049). During the study, approximately 17% of all participants reported experiencing adverse reactions that lasted between 1 to 3 weeks before disappearing.

[CONCLUSION] BoNT is an effective and safe method for treating CD. The maximum remission rates of patients after their first injections are influenced by the duration of their disease. Thus, treatment using BoNT injections must be administered as soon as possible.