Objective: Evaluate the impact of one injection cycle of abobotulinumtoxinA (AboBoNT-A; Dysport®) on the clinical characteristics of cervical dystonia (CD).

Background: The pharmacologic effects of botulinum neurotoxin type A (BoNT-A) are transient and repeat injections are required for long-term efficacy, however the impact of treatment on the natural history of treated CD is not well characterized. 

Methods: The MetaCD database includes data from 2 observational international studies (INTEREST IN CD1 & 2) and 1 US registry (ANCHOR-CD). This analysis focused on the subgroup of 1091 subjects who were treated with AboBoNT-A. Assessments were performed at baseline/first injection (V1) and end of cycle/next injection (V2) and clinical efficacy assessments included the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and Tsui tremor scores.

Results: Overall, 66.2% were female; mean age was 56.1 years and median time since diagnosis was 6.0 years. The majority (84.4%) had received previous BoNT treatment (median time from starting BoNT treatment: 3.7 years; median time since last injection: 3.6 months). For all subjects the median interval between V1/V2 was 99 days (~3.3 months); of these 73.9% had an interval of 12-16 weeks and 23.1% had an interval >16 weeks.  Overall, the proportion of subjects categorized as having severe tremor (Tsui) reduced from 12.1% at V1 to 9.4% at V2. Mean±SD TWSTRS total scores improved from 33.5±12.4 at V1 to 30.0±12.9 at V2 (mean [95%CI], decrease of -3.5 [-4.1;-2.9]); severity scores decreased from 17.3±5.2 to 15.7±5.5 (-1.7 [-1.9;-1.4]); disability scores from 9.9±6.2 to 8.8±6.1 (-1.1 [-1.3;-0.8]) and pain scores from 6.3±4.7 to 5.7±4.7 (-0.6 [-0.9;-0.4]).  Improvements in TWSTRS scores from 1st injection to end of treatment cycle were also seen irrespective of treatment interval.

Conclusions: These data indicate that the clinical symptoms of CD may not fully return to baseline following an injection of AboBoNT-A. More research is required to investigate whether this improvement may be attributed to a residual therapeutic effect or a potential disease modifying effect of repetitive BoNT-A injections.  Thus, investigation of this effect will require further analysis of the evolution of CD severity over several injection cycles and longer treatment intervals.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/clinical-effects-are-persistent-at-the-end-of-one-abobotulinumtoxina-injection-cycle-in-cervical-dystonia-results-from-a-meta-analysis-of-1091-subjects/