Title
Examining the role of intrinsic and reflexive contributions to ankle joint hyper-resistance treated with botulinum toxin-A
Author
van’t Veld, Ronald C. (University of Twente)
Flux, Eline (Vrije Universiteit Amsterdam)
van Oorschot, Wieneke (Sint Maartenskliniek, Nijmegen)
Schouten, A.C. (TU Delft Biomechanical Engineering; University of Twente) 
van der Krogt, Marjolein M. (Vrije Universiteit Amsterdam)
van der Kooij, H. (TU Delft Support Biomechanical Engineering; University of Twente)
Vos-van der Hulst, Marije (Sint Maartenskliniek, Nijmegen)
Keijsers, Noël L.W. (Radboud University Medical Center; Sint Maartenskliniek, Nijmegen)
van Asseldonk, Edwin H.F. (University of Twente)
Department
Biomechanical Engineering
Date
2023
Abstract
Background: Spasticity, i.e. stretch hyperreflexia, increases joint resistance similar to symptoms like hypertonia and contractures. Botulinum neurotoxin-A (BoNT-A) injections are a widely used intervention to reduce spasticity. BoNT-A effects on spasticity are poorly understood, because clinical measures, e.g. modified Ashworth scale (MAS), cannot differentiate between the symptoms affecting joint resistance. This paper distinguishes the contributions of the reflexive and intrinsic pathways to ankle joint hyper-resistance for participants treated with BoNT-A injections. We hypothesized that the overall joint resistance and reflexive contribution decrease 6 weeks after injection, while returning close to baseline after 12 weeks. Methods: Nine participants with spasticity after spinal cord injury or after stroke were evaluated across three sessions: 0, 6 and 12 weeks after BoNT-A injection in the calf muscles. Evaluation included clinical measures (MAS, Tardieu Scale) and motorized instrumented assessment using the instrumented spasticity test (SPAT) and parallel-cascade (PC) system identification. Assessments included measures for: (1) overall resistance from MAS and fast velocity SPAT; (2) reflexive resistance contribution from Tardieu Scale, difference between fast and slow velocity SPAT and PC reflexive gain; and (3) intrinsic resistance contribution from slow velocity SPAT and PC intrinsic stiffness/damping. Results: Individually, the hypothesized BoNT-A effect, the combination of a reduced resistance (week 6) and return towards baseline (week 12), was observed in the MAS (5 participants), fast velocity SPAT (2 participants), Tardieu Scale (2 participants), SPAT (1 participant) and reflexive gain (4 participants). On group-level, the hypothesis was only confirmed for the MAS, which showed a significant resistance reduction at week 6. All instrumented measures were strongly correlated when quantifying the same resistance contribution. Conclusion: At group-level, the expected joint resistance reduction due to BoNT-A injections was only observed in the MAS (overall resistance). This observed reduction could not be attributed to an unambiguous group-level reduction of the reflexive resistance contribution, as no instrumented measure confirmed the hypothesis. Validity of the instrumented measures was supported through a strong association between different assessment methods. Therefore, further quantification of the individual contributions to joint resistance changes using instrumented measures across a large sample size are essential to understand the heterogeneous response to BoNT-A injections.
Subject
BoNT-A injections
Instrumented SPAT
Joint resistance
Spasticity
System identification
To reference this document use:
http://resolver.tudelft.nl/uuid:c01a254e-d5cd-4a04-8b21-49ea4a2bcbfa
DOI
https://doi.org/10.1186/s12984-023-01141-8
ISSN
1743-0003
Source
Journal of NeuroEngineering and Rehabilitation, 20 (1)
Part of collection
Institutional Repository
Document type
journal article
Rights
© 2023 Ronald C. van’t Veld, Eline Flux, Wieneke van Oorschot, A.C. Schouten, Marjolein M. van der Krogt, H. van der Kooij, Marije Vos-van der Hulst, Noël L.W. Keijsers, Edwin H.F. van Asseldonk