Passive Properties of the Wrist and Fingers Following Chronic Hemiparetic Stroke: Interlimb Comparisons in Persons With and Without a Clinical Treatment History That Includes Botulinum Neurotoxin

Abstract

Background: Neural impairments that follow hemiparetic stroke may negatively affect passive muscle properties, further limiting recovery. However, factors such as hypertonia, spasticity, and botulinum neurotoxin (BoNT), a common clinical intervention, confound our understanding of muscle properties in chronic stroke.Objective: To determine if muscle passive biomechanical properties are different following prolonged, stroke-induced, altered muscle activation and disuse.Methods: Torques about the metacarpophalangeal and wrist joints were measured in different joint postures in both limbs of participants with hemiparetic stroke. First, we evaluated 27 participants with no history of BoNT; hand impairments ranged from mild to severe. Subsequently, seven participants with a history of BoNT injections were evaluated. To mitigate muscle hypertonia, torques were quantified after an extensive stretching protocol and under conditions that encouraged participants to sleep. EMGs were monitored throughout data collection.Results: Among participants who never received BoNT, no significant differences in passive torques between limbs were observed. Among participants who previously received BoNT injections, passive flexion torques about their paretic wrist and finger joints were larger than their non-paretic limb (average interlimb differences = +42.0 ± 7.6SEM Ncm, +26.9 ± 3.9SEM Ncm, respectively), and the range of motion for passive finger extension was significantly smaller (average interlimb difference = −36.3° ± 4.5°SEM; degrees).Conclusion: Our results suggest that neural impairments that follow chronic, hemiparetic stroke do not lead to passive mechanical changes within the wrist and finger muscles. Rather, consistent with animal studies, the data points to potential adverse effects of BoNT on passive muscle properties post-stroke, which warrant further consideration.

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

“…In a recent study that compared passive properties of spastic wrist and finger flexors in chronic stroke survivors, no significant differences in passive torques between affected and contralateral limbs were found in those who never received BoNT. In contrast, passive torques were significantly higher and passive range of motion of wrist and finger extension was significantly smaller in the affected limb than the contralateral limb in those who received BoNT injections to these muscles, on average, 4 and 1/2 years ago [43]. In another study [44], stroke subjects received either BoNT or placebo (normal saline) injections when spasticity was first detected in the arm flexors.…”

The Effectiveness of Botulinum Toxin Injections to Treat Post-Stroke Arm Dysfunction

“…44 More recently, research has shown that repeated use of BoNT may also lead to decreased passive muscle capacity. 13 Studies done in rodents indicated that BoNT injection led to a decrease in function, range of motion, and an increase in passive resistance. [45][46][47][48] A systematic review examining BoNT injections in humans and animals found similar results, such as lingering muscle atrophy and changes in muscle elasticity.…”

“…However, recent evidence suggests that the nature of the toxin may lead to muscle shortening and a restricted range of motion if repeatedly injected. 13 This paper will provide a scoping review on the effectiveness of Botulinum Toxin for post-stroke arm dysfunction and its overall effect on the patient.…”

Peripheral nerve blocks of wrist and finger flexors can increase hand opening in chronic hemiparetic stroke

“…The presence of hyperactive stretch reflexes, in comparison, may not play a major role in stroke disability ( 5 ) compared to the expression of said flexion synergy ( 11 ). As passive muscle properties are also largely unchanged ( 4 , 12 ), it is likely the overactive wrist and finger flexors ( particularly the flexion synergy) and extensor weakness that limits hand use in stroke.…”

“…Some individuals even develop neutralizing antibodies to the toxin, rendering the intervention ineffective with repeat injections ( 28 ). Finally, evidence also indicates potential long-term concerns related to increased muscle passive stiffness, possibly due to muscle extracellular matrix proliferation ( 12 , 29–32 ). An alternative worth exploring is the use of FES-based methods that provide instantaneous, controllable, and reversible blocking of peripheral nerve transmission ( 33–35 ).…”