[An analysis of treatment of the Russian group of patients in the international observational study «Factors influencing response to botulinum toxin type A in patients with idiopathic cervical dystonia»].
AIM
The analysis of the results of treatment of the Russian patient population in the frame of international, multicenter, non-interventional study of CD, the primary purpose of which was to determine the response rate to therapy with BTA at the peak of the effect: after one course of injections in settings of routine practice, as well as the results of application of modern definition for "response" to treatment with BTA.


MATERIAL AND METHODS
In Russia 60 patients with idiopathic CD were included. Patients were classified as «responders» according to the following 4 criteria: effect size (improvement by ≥ 25% assessed by TWSTRS); effect duration: ≥ 12 weeks interval between the BTA injection and the day when the patient reported a decrease of clinical effect, indicating the need for repeated treatment; good tolerability of treatment (no treatment-related serious adverse events (AEs) during the study period); patient-reported Clinical Global Improvement (CGI) score is +2 («significant improvement») or +3 («very significant improvement») at the visits 2 or 3.


RESULTS AND CONCLUSION
In the Russian population, patients with a ≥ 25% improvement by TWSTRS scale at visit 2 (peak effect) accounted for 88.3%. Most of patients (81.6%) and physicians (81.7%) evaluated the efficacy of therapy as a «significant improvement» or «very significant improvement» by CGI. The criterion of the effect duration was achieved in 50% of cases. The BTA therapy was well tolerated (no severe AEs related to treatment) in 98.3% of patients. Overall, 40% of all patients met all the criteria for response to BTA treatment. According to the analysis of the general population, a high degree of response was observed for the effect size (73.6%), tolerability (97.5%) and patient-reported global clinical improvement (69.8%). Subjective assessment of the duration of the effect was achieved in 49.3% of patients, with 28.6% of patients considered as responders. Most patients met three of the four criteria. The proposed multifactorial definition of «response» may be of practical use for routine practice.