Effect of post-stroke spasticity on voluntary movement of the upper limb.
Hadar Lackritz, Yisrael Parmet, Silvi Frenkel-Toledo and 6 others
PMID 33985543WHAT IT FOUND
Spasticity, measured by the threshold at which muscle resistance begins, strongly predicts the quality of voluntary reaching movements in stroke survivors.
This effect is distinct from overall motor impairment scores, suggesting that treating spasticity may improve movement quality beyond what general rehabilitation achieves.
Key findings
01Spasticity measured by the Tonic Stretch Reflex Threshold (TSRT) was significantly related to the quality of voluntary movement, as quantified by Hellinger’s distance and mean elbow velocity.
02The effect of spasticity on movement quality was independent of overall motor impairment (Fugl-Meyer scores), meaning TSRT explained movement variance that clinical scales did not.
03Stroke survivors with mild-to-moderate impairment showed the poorest movement quality at mid-range spasticity thresholds, rather than a simple linear relationship where more spasticity always meant worse movement.
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
Only elbow spasticity was measured; spasticity in shoulder or wrist muscles may have influenced the results. The study included participants in the sub-acute phase (3 weeks to 6 months); results may differ in chronic stroke (>6 months). Participants were excluded if they were taking anti-spasticity medications, which limits generalizability to patients currently managed with such drugs. The relationship between spasticity and movement quality was non-linear for mild-to-moderate cases, complicating simple clinical interpretation.
Declared interests
Funded by Canadian Institutes of Health Research, Azrieli Foundation, International Development Research Center, Israel Science Foundation, and Leona M. and Harry B. Helmsley Charitable Trust. No commercial conflicts declared.
The easy way to misread this
Do not assume that lower spasticity (higher TSRT) always leads to better movement quality. In patients with mild-to-moderate impairment, those with mid-range spasticity thresholds had the worst movement quality, while those with very high or very low thresholds had better outcomes.