Abstract
Spasticity is a common motor impairment following stroke. The assessment of the extent of spasticity is achieved clinically using the Modified Ashworth Scale (MAS) and/or the Tardieu Scale, and these are often used to determine the efficacy of pharmacological and/or rehabilitation therapies used to treat spasticity. While both tests are qualitative in nature, the Tardieu Scale assesses the resistance to joint motion at various speeds, providing the clinician with more information about the dependence of the perceived resistance on the speed of joint rotation. Our goal in this chapter is to provide insight into how the “catch”, which reflects the resistance to joint motion during the MAS and the Tardieu Scale, varies as a function of joint rotation speed, and to assess the contribution of the reflex response to the catch. Clinical assessments of spasticity, including the MAS, were performed by a trained clinician on chronic stroke survivors. Separately, the elbow joint was moved passively at three different speeds during which the elbow angle and muscle activity of the medial and lateral biceps were measured using an electrogoniometer and electromyography (EMG), respectively. The quantitative measurements demonstrate large variability in the catch angle and the EMG responses as a function of joint rotation speed among stroke survivors with the same clinical MAS score. As expected, participants with a higher clinical MAS score showed an increased occurrence of catches earlier during elbow joint rotation (i.e., larger catch angle). However, not all participants who demonstrated a catch showed an EMG response in the biceps, suggesting the contribution of other muscles and/or the presence of a non-neural or mechanical component to the resistance. Furthermore, in participants who showed an EMG response, the catch angle decreased as a function of joint rotation speed (i.e., the catch angle became smaller with increased speed) due to a constant latency between EMG onset and the catch. In addition, the resistance to passive elbow joint rotation was quantified before and every two weeks after injections of botulinum toxin (BoNT) in the elbow flexors of two chronic stroke survivors for six weeks. The reduction in EMG with BoNT did not necessarily reduce the passive resistance or catch angle, suggesting that overactivity in muscles other than those injected or non-neural changes in the muscles injected likely contributed to the passive resistance.
Original language | English (US) |
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Title of host publication | Spasticity and Muscle Stiffness |
Subtitle of host publication | Restoring Form and Function |
Publisher | Springer International Publishing |
Pages | 47-62 |
Number of pages | 16 |
ISBN (Electronic) | 9783030969004 |
ISBN (Print) | 9783030968991 |
DOIs | |
State | Published - Jan 1 2022 |
Keywords
- EMG
- Joint rotation
- Spasticity
- Stretch reflex
- Stroke
ASJC Scopus subject areas
- General Medicine
- General Health Professions