Comprehensive Assessment of the Time Course of Biomechanical, Electrophysiological and Neuro-Motor Effects after Botulinum Toxin Injections in Elbow Flexors of Chronic Stroke Survivors with Spastic Hemiplegia: A Cross Sectional Observation Study

Abstract

Botulinum neurotoxin (BoNT) is commonly used to manage focal spasticity in stroke survivors. This study aimed to a perform comprehensive assessment of the effects of BoNT injection. Twelve stroke subjects with spastic hemiplegia (age: 52.0 ± 10.1 year; 5 females) received 100 units of BoNT to the spastic biceps brachii muscles. Clinical, biomechanical, electrophysiological, and neuro-motor assessments were performed one week (wk) before (pre-injection), 3 weeks (wks) after, and 3 months (mons) after BoNT injection. BoNT injection significantly reduced spasticity, muscle strength, reflex torque, and compound muscle action potential (CMAP) amplitude of spastic elbow flexors (all p < 0.05) during the 3-wks visit, and these values return to the pre-injection level during the 3-mons visit. Furthermore, the degree of reflex torque change was negatively correlated to the amount of non-reflex component of elbow flexor resistance torque. However, voluntary force control and non-reflex resistance torque remained unchanged throughout. Our results revealed parallel changes in clinical, neurophysiological and biomechanical assessment after BoNT injection; BoNT injection would be more effective if hypertonia was mainly mediated by underlying neural mechanisms. BoNT did not affect voluntary force control of spastic muscles.

Does spasticity correlate with motor impairment in the upper and lower limbs in ambulatory chronic stroke survivors?

“…Majority of subjects had a history of botulinum toxin injections for spasticity management (>3 mos). It is known that the effect of botulinum toxin on spasticity is temporary and returns to the baseline in approximately 3 mos 31 . The effect of injections on the results in this study is likely negligible.…”

“…It is known that the effect of botulinum toxin on spasticity is temporary and returns to the baseline in approximately 3 mos. 31 The effect of injections on the results in this study is likely negligible. A sample size of 28 subjects is relatively small, which may not allow us to detect a weak correlation between two variables in correlation analyses and a weak association between a covariate and the response variable in multiple regression analyses.…”