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Updated: Oct 23, 2025
A High Content Imaging Assay for Identification of Botulinum Neurotoxin Inhibitors
Published on: November 14, 2014
Investigating Inducible Muscle Overactivity in Acquired Brain Injury and the Impact of Botulinum Toxin A
Ian J Baguley1, Hannah L Barden2, Karen Byth3
1From the Brain injury Rehabilitation Service, Westmead Hospital, Wentworthville; The University of Sydney School of Medicine, Sydney.
Objective:
To investigate the pattern of change in muscle overactivity during repetitive grasp/release using dynamic computerized dynamometry (DCD; objective 1) and the effect of botulinum toxin A (BTX-A; objective 2).
Design:
Secondary analysis of an observational cohort study.
Setting:
Hospital outpatient spasticity management service.
Participants:
A convenience sample (N=65), comprising adults with upper motor neuron syndrome affecting the arm after acquired brain injury (ABI; n=38) and participants without ABI (n=27).
Interventions:
After clinical assessment, a subgroup of participants with ABI (n=28) underwent BTX-A injections as part of their spasticity management.
Main Outcome Measures:
Post hoc DCD data processing extracted the values of minimum force generation between 10 sequential contractions. The pattern of change was analyzed.
Results:
The ABI injected group exerted greater force at baseline than both other groups (ABI injected=1.04 kg, ABI noninjected=0.74 kg, participants without ABI=0.53 kg; P=.011). After the first contraction, minimum force values increased for all groups and were greatest in the ABI injected group. With subsequent cycles, the group without ABI showed a linear pattern of decreasing force generation, whereas both ABI groups showed a quadratic increasing pattern, which was of greater magnitude in the ABI injected group. After injection, values for the ABI injected group showed a 51% reduction in inducible muscle overactivity (P=.003) to magnitudes similar to those of the ABI noninjected group.
Conclusions:
This study showed that hand relaxation deteriorated during repetitive movements in people with spasticity, a feature hypothesized to adversely influence everyday hand function. After BTX-A injection, the magnitude but not the pattern of this inducible muscle overactivity improved.
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