Relief of pain associated with spasticity in adult patients after treatment with onabotulinumtoxinA: Post hoc observational results from the ASPIRE study.

The study was observational and uncontrolled, with no placebo or comparison group, so it cannot prove that onabotulinumtoxinA caused the observed improvements. The analysis was post hoc and exploratory, meaning hypotheses were not prespecified and results should be interpreted with caution. Patient-reported outcomes were self-evaluations that could be influenced by expectations or bias, as the study was not blinded. The study did not differentiate between types of pain (e.g., neuropathic vs. musculoskeletal) or assess whether pain was localized to spastic muscles, limiting understanding of the mechanism of relief. Sample sizes decreased significantly at later treatment sessions, making data from later time points less reliable. AbbVie, the manufacturer of onabotulinumtoxinA, funded the study and participated in its design, analysis, and publication, which may introduce bias.

AbbVie Inc. funded the study and participated in the study design, research, analysis, data collection, interpretation of data, reviewing, and approval of the publication. Several authors are employees of AbbVie or received honoraria from AbbVie and other pharmaceutical companies.

Do not interpret the reduction in pain scores as definitive proof of efficacy. Because this was an uncontrolled observational study, the improvements cannot be separated from natural history, regression to the mean, or the placebo effect. The lack of a control group means these results describe an association, not a causal effect.