Cumulative effects of long-term treatment with abobotulinumtoxinA in cervical dystonia: Findings from a prospective, observational study

Objective: Patients with cervical dystonia (CD) require regular injections of botulinum neurotoxin type A (BoNT-A) to maintain treatment effectiveness. In this secondary analysis of a large routine-practice study, we assessed the response to abobotulinumtoxinA over repeated cycles and compared the responses of patients previously naive to BoNT treatment to those already treated with BoNT-A. Methods: INTEREST IN CD2 was a prospective, 3-year, observational study following CD patients treated with BoNT-A. Patients were assessed at each injection visit using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and Tsui scale; patient satisfaction with symptom control (previous cycle) was recorded. Results: This analysis included 466 patients treated with abobotulinumtoxinA over 3 years. TWSTRS-Total scores continually decreased; the mean +/- SD reduction from baseline to 36 months was -7.4 +/- 11.9. BoNT-naive patients tended to show greater reductions in TWSTRS scores than already treated patients, particularly in the first 6 months. Incremental improvements were also seen in Tsui-tremor scores. Overall levels of patient satisfaction at peak effect (84.1-91.2%) were consistently higher than at the end of cycle (47.2-53.2%). The most frequently reported adverse events were dysphagia (6.8%) and muscular weakness (3.7%). Conclusions: These data support the long-term effectiveness and safety of abobotulinumtoxinA in a real-world setting.