The Effects of Botulinum Toxin Injections on Spasticity and Motor Performance in Chronic Stroke with Spastic Hemiplegia

Abstract

Spastic muscles are weak muscles. It is known that muscle weakness is linked to poor motor performance. Botulinum neurotoxin (BoNT) injections are considered as the first-line treatment for focal spasticity. The purpose of this study was to quantitatively investigate the effects of BoNT injections on force control of spastic biceps brachii muscles in stroke survivors. Ten stroke survivors with spastic hemiplegia (51.7 ± 11.5 yrs; 5 men) who received 100 units of incobotulinumtoxinA or onabotulinumtoxinA to the biceps brachii muscles participated in this study. Spasticity assessment (Modified Ashworth Scale (MAS) and reflex torque) and muscle strength of elbow flexors, as well as motor performance assessment (force variability of submaximal elbow flexion) were performed within one week before (pre-injection) and 3~4 weeks (3-wk) after BoNT injections. As expected, BoNT injections reduced the MAS score and reflex torque, and elbow flexor strength on the spastic paretic side. However, motor performance remained within similar level before and after injections. There was no change in muscle strength or motor performance on the contralateral arm after BoNT injections. The results of this study provide evidence that BoNT injections can reduce spasticity and muscle strength, while motor performance of the weakened spastic muscle remains unchanged.

A New Definition of Poststroke Spasticity and the Interference of Spasticity With Motor Recovery From Acute to Chronic Stages

“…47,48 It is also difficult for them to maintain a constant force output on the spastic-paretic side as compared with the contralateral side. 41,[49][50][51] The weaker the spastic muscle, the greater the force variability that was observed. 41 Spastic muscles are weak muscles.…”

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

“…The spasticity-related spontaneous motor neuron firing is not under voluntary control, and could be viewed as "motor noise" during voluntary activation. As such, they may make it difficult for stroke survivors to perform voluntary actions with spastic muscles, such as to initiate or terminate a hand grip [13,14] or maintain a constant force output [12,[15][16][17]. In other words, spasticity interferes with motor performance of spastic muscles [9].…”

“…This differentiation is important because BoNT injections also induce muscular changes and alter muscle stiffness [30]. It was found that both the MAS score and reflex torque of elbow flexor muscles significantly decreased 3 wks after BoNT injections, the non-reflex torque remained unchanged [17]. In a longitudinal study, the reflex torque of wrist flexors of stroke survivors decreased at 4 wks after BoNT injections, and returned to baseline levels at 12 wks.…”

“…In a longitudinal study, the reflex torque of wrist flexors of stroke survivors decreased at 4 wks after BoNT injections, and returned to baseline levels at 12 wks. Similarly, the non-reflex torque remains unchanged after the treatment [17]. Electrophysiological assessment has also been used to quantify the BoNT effects [31][32][33].…”

Neurophysiological Factors Affecting Muscle Innervation Zone Estimation Using Surface EMG: A Simulation Study

“…For example, how IZ is distributed is an essential component for understanding muscle morphology and its alterations in diseased states [1][2][3][4][5]. In clinical practice, identification of muscle IZ can help facilitate botulinum toxin injection for spasticity treatment [6][7][8][9]. Knowledge of muscle IZ is also helpful for episiotomy during child delivery to minimize the risk of sphincter denervation [10].…”