Factors influencing treatment outcomes in botulinum toxin–naïve patients with cervical dystonia

Background Intramuscular botulinum neurotoxin (BoNT) is currently considered the gold standard treatment for cervical dystonia (CD). Therefore, the primary goal of the study was to explore the associations between eleven variables and patient-reported efficacy of BoNT treatment. Methods We retrospectively analysed data from 48 BoNT-naïve CD patients who received ultrasound-guided BoNT treatment between March 2022 and December 2025. Results Significant pairwise associations were found only between the ordinal outcome variable and the average dystonic electromyography (EMG) activity of the injected muscles ( p = 0.025) and the severity of tremulous/jerky movements ( p = 0.032). A significant interaction between the average dystonic EMG activity of the injected muscles and the status of tremulous/jerky movements was identified ( p = 0.002). A strong positive association between the average dystonic EMG activity of the injected muscles and the outcome was present only in patients with tremulous/jerky movements ( p < 0.001). Patients with tremulous/jerky CD were characterized by a longer disease duration (60 vs. 15 months) and less pronounced average abnormal posturing (18.7° vs. 26.8°) compared to those without tremulous/jerky movements. Conclusion We found a significant interaction between average dystonic EMG activity of the injected muscles and the presence of tremulous/jerky movements, highlighting the potential clinical relevance of electrophysiological muscle activity in this clinical phenotype. However, our observations should be interpreted cautiously because of the retrospective design and limited sample size.