Botulinum toxin A modifies nociceptive withdrawal reflex in subacute stroke patients.

Elena Alvisi,Cristina Tassorelli,Mariano Serrao,Francesco Pierelli,Armando Perrotta,Carmela Conte,Silvano Cristina,Paolo Prunetti,Enrico Alfonsi,Giorgio Sandrini

doi:10.1002/brb3.1069

Abstract

ObjectivesThe aims of this study were to evaluate the pattern of the nociceptive withdrawal reflex (NWR) of the upper limb at rest and after injection of Botulinum toxin type A (BoNT‐A) in poststroke subacute hemiparetic patients.MethodsFourteen patients with poststroke subacute hemiparesis underwent clinical and instrumental evaluation and BoNT‐A injection. Painful electrical stimulation was applied to induce the NWR. Baseline EMG activity and NWR recordings (EMG and kinematic response) were performed at T0, one month (T1), and three months (T2) after the BoNT‐A injection, as were Modified Ashworth Scale (MAS) and Functional Independence Measure (FIM) scores.ResultsComparison of results at T0, T1, and T2 revealed significant changes in the MAS score for the elbow (p < 0.001) and wrist joints (p < 0.001) and in the FIM score at T0 and T2. BoNT‐A injection had a significant effect on both NWR amplitude and baseline EMG activity in the posterior deltoid (PD) and flexor carpi radialis (FCR) muscles as well as in all averaged muscles. Analysis of elbow kinematics before and after treatment revealed that the reflex probability rates were significantly higher at T1 and T2 than at T0.ConclusionInjection of BoNT‐A in the subacute phase of stroke can modify both the baseline EMG activity and the NWR‐related EMG responses in the upper limb muscles irrespective of the site of injection; furthermore, the reflex‐mediated defensive mechanical responses, that is, shoulder extension and abduction and elbow flexion, increased after treatment. BoNT‐A injection may be a useful treatment in poststroke spasticity with a potential indirect effect on spinal neurons.

Highlights

Upper limb spasticity is a frequent complication of stroke that greatly interferes with hand function, motor relearning, recovery of voluntary movements, positioning, and hygiene; it can cause pain, with activity limitation and loss of dexterity (Rosales et al, 2016; Sommerfeld, Eek, Svensson, Holmqvist, & von Arbin, 2003)
The upper limb nociceptive withdrawal reflex (NWR) was used as a tool to evaluate the effect of botulinum toxin type A (BoNT-A) administration on the excitability of spinal cord neurons in the subacute phase of stroke
Our assumption was that this investigation may help to shed light both on the plastic rearrangement occurring at the level of the NWR-mediating neurons, and on the changes induced by BoNT-A injection that may, potentially, prevent the development of spasticity and promote a better motor recovery

Summary

Introduction

Upper limb spasticity is a frequent complication of stroke that greatly interferes with hand function, motor relearning, recovery of voluntary movements, positioning, and hygiene; it can cause pain, with activity limitation and loss of dexterity (Rosales et al, 2016; Sommerfeld, Eek, Svensson, Holmqvist, & von Arbin, 2003). For this reason, the pharmacological and rehabilitation treatment of spasticity is a primary objective in stroke patients (Bethoux, 2015). In addition to reducing spasticity, BoNT-A may, by inhibiting the release of pain modulators (e.g. substance P), result in a decrease in pain (Arezzo, 2002)

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