Responsiveness of the Australian Spasticity Assessment Scale to botulinum neurotoxin injection into spastic wrist flexors after acquired brain injury

The Australian Spasticity Assessment Scale (ASAS) is a relatively new scale used to rate the severity of spasticity. Although the reliability of the ASAS has been investigated, its ability to detect a clinically important change (responsiveness) has not. The objective of this study was to investigate the responsiveness of the ASAS in adult patients with acquired brain injury-related wrist flexor spasticity treated with botulinum neurotoxin A. The responsiveness of the ASAS was assessed by the standardized response mean at the group level. At the individual level, responsiveness was assessed by the percentage of responders and nonresponders. Those who had at least a 1 grade reduction in spasticity severity were considered responders. In addition, the magnitude of the goniometric change in R1 (angle of catch response) across the responders and nonresponders was studied as a distribution of frequency. Significant improvements in R1 and ASAS were achieved with the treatment. The standardized response mean based on the ASAS grades was 1.50 with a 95% confidence interval of 1.16-1.89. At the individual level, 40 of all cases (78.4%) were responders, and 11 (21.6%) were nonresponders. Three of the 11 nonresponders (27.3%) improved R1 beyond the 10 ° margin of error (20, 50, and 50 °). In contrast, the percentage of responders who had a change within the margin of error was 27.5% (11 out of 40). Although ASAS can reveal a decrease in wrist flexor spasticity, it has some shortcomings in detecting the potentially clinically important response at the individual level.