Clinical Relevance of the Tonic Stretch Reflex Threshold and μ as Measures of Upper Limb Spasticity and Motor Impairment After Stroke.
Daniele Piscitelli, Joy Khayat, Anatol G Feldman and 1 others
PMID 39945415WHAT IT FOUND
A portable device measuring the elbow's stretch reflex threshold predicted 72% of upper limb motor impairment variance in stroke survivors.
This offers a more objective way to define the specific joint range where muscle activation becomes disordered compared to standard clinical scales.
Key findings
01The tonic stretch reflex threshold (TSRT) and velocity-sensitivity parameter (μ) significantly predicted upper limb motor impairment scores, explaining 72% of the variance in the shoulder-elbow section of the Fugl-Meyer Assessment.
02TSRT values were significantly higher in the acute/early subacute phase compared to the chronic phase, while the velocity-sensitivity parameter (μ) did not differ significantly between these stroke chronicity groups.
03The TSRT angle identifies the boundary of the 'active control range,' distinguishing the joint angles where normal movement is possible from the 'spasticity range' where muscle activation becomes disordered.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study is cross-sectional, meaning it compares different people at different times after stroke rather than following the same individuals over time. It cannot prove that changes in TSRT cause changes in motor recovery or predict future outcomes for a single patient. The measurement requires specialized equipment (the Montreal Spasticity Measure) and training, which may not be available in most clinical settings. The Modified Ashworth Scale, used as a comparator, has known reliability issues and only captures one aspect of spasticity, which may weaken the strength of the correlations. The sample was heterogeneous regarding stroke type and lesion location, and the study did not analyze whether the TSRT's predictive power differs based on these factors.
Declared interests
The authors declared no potential conflicts of interest. Funding was provided by the Canadian Institutes of Health Research and the Centre for Interdisciplinary Research in Rehabilitation.
The easy way to misread this
Do not interpret the high correlation between TSRT and Fugl-Meyer scores as evidence that the TSRT is a validated clinical tool ready for routine use. The study establishes a statistical relationship in a pooled dataset, but it does not demonstrate that using this measure to guide therapy improves patient outcomes compared to standard care.