Botulinum toxin A modifies nociceptive withdrawal reflex in subacute stroke patients

The effectiveness of early interventions for post-stroke spasticity: a systematic review

PURPOSE

To synthesize evidence on the effect of early post-stroke spasticity interventions.

METHODS

Systematic literature search (PubMed, Embase, and Web of Science) encompassing studies on spasticity reducing interventions within 3 months post stroke on outcome defined within the International Classification of Functioning (ICF).

RESULTS

In total, 27 studies were identified with n = 1.658 cases. Botulinum toxin (2-12 weeks; 10 studies, n = 794) showed consistent and significant reduced spasticity by Modified Ashworth Scale (MAS) or electromyography (EMG). Electrical muscle stimulation (1-8 weeks; 6 studies, n = 335) showed lower MAS/Composite Spasticity Scale scores in 4 studies. Transcranial stimulation (3 studies; n = 131), oral spasmolytics (1 study; n = 38), shockwave (1 study; n = 40), orthotics (3 studies; n = 197 and robot-assisted therapy (3 studies; n = 123) showed inconclusive results. Effects on ICF activity domain could not be established due to limited data and large outcome measures heterogeneity. One out of two studies showed significant benefit for early compared to late BoNT intervention (< 90 vs> 90 days).

CONCLUSION

This study provides evidence for early applied (<3 months) BoNT to effectively reduce spasticity and probable effectiveness of electrical stimulation. Establishing effects of interventions in the acute/hospitalization phase (<7 days) needs further work, specifically on the ICF activity domain. Standardization of outcome measures is required.

AbobotulinumtoxinA Doses in Upper and Lower Limb Spasticity: A Systematic Literature Review

Disabling limb spasticity can result from stroke, traumatic brain injury or other disorders causing upper motor neuron lesions such as multiple sclerosis. Clinical studies have shown that abobotulinumtoxinA (AboBoNT-A) therapy reduces upper and lower limb spasticity in adults. However, physicians may administer potentially inadequate doses, given the lack of consensus on adjusting dose according to muscle volume, the wide dose ranges in the summary of product characteristics or cited in the published literature, and/or the high quantity of toxin available for injection. Against this background, a systematic literature review based on searches of MEDLINE and Embase (via Ovid SP) and three relevant conferences (2018 to 2020) was conducted in November 2020 to examine AboBoNT-A doses given to adults for upper or lower limb muscles affected by spasticity of any etiology in clinical and real-world evidence studies. From the 1781 unique records identified from the electronic databases and conference proceedings screened, 49 unique studies represented across 56 publications (53 full-text articles, 3 conference abstracts) were eligible for inclusion. Evidence from these studies suggested that AboBoNT-A dose given per muscle in clinical practice varies considerably, with only a slight trend toward a relationship between dose and muscle volume. Expert-based consensus is needed to inform recommendations for standardizing AboBoNT-A treatment initiation doses based on muscle volume.

Precise quantification of the time course of voluntary activation capacity following Botulinum toxin injections in the biceps brachii muscles of chronic stroke survivors

Background

Spasticity is a key motor impairment that affects many hemispheric stroke survivors. Intramuscular botulinum toxin (BT) injections are used widely to clinically manage spasticity-related symptoms in stroke survivors by chemically denervating muscle fibers from their associated motor neurons. In this study, we sought to understand how BT affects muscle activation, motor unit composition and voluntary force generating capacity over a time period of 3 months. Our purpose was to characterize the time course of functional changes in voluntary muscle activity in stroke survivors who are undergoing BT therapy as part of their physician-prescribed clinical plan.

Method

Our assessment of the effects of BT was based on the quantification of surface electromyogram (sEMG) recordings in the biceps brachii (BB), an upper arm muscle and of voluntary contraction force. We report here on voluntary force and sEMG responses during isometric elbow contractions across consecutive recording sessions, spread over 12 weeks in three segments, starting with a preliminary session performed just prior to the BT injection. At predetermined time points, we conducted additional clinical assessments and we also recorded from the contralateral limbs of our stroke cohort. Eight subjects were studied for approximately 86 experimental recording sessions on both stroke-affected and contralateral sides.

Results

We recorded an initial reduction in force and sEMG in all subjects, followed by a trajectory with a progressive return to baseline over a maximum of 12 weeks, although the minimum sEMG and minimum force were not always recorded at the same time point. Three participants were able to complete only one to two segments. Slope values of the sEMG-force relations were also found to vary across the different time segments. While sEMG-force slopes provide assessments of force generation capacity of the BT injected muscle, amplitude histograms from novel sEMG recordings during the voluntary tasks provide additional insights about differential actions of BT on the overall motor unit (MU) population over time.

Conclusions

The results of our study indicate that there are potential short term as well as long term decrements in muscle control and activation properties after BT administration on the affected side of chronic stroke survivors. Muscle activation levels as recorded using sEMG, did not routinely return to baseline even at three months’ post injection. The concurrent clinical measures also did not follow the same time course, nor did they provide the same resolution as our experimental measures. It follows that even 12 weeks after intramuscular BT injections muscle recovery may not be complete, and may thereby contribute to pre-existing paresis.

Stimulus predictability moderates the withdrawal strategy in response to repetitive noxious stimulation in humans

Innate defensive behaviors such as reflexes are found across all species, constituting preprogrammed responses to external threats that are not anticipated. Previous studies indicated that the excitability of the reflex arcs like spinal nociceptive withdrawal reflex (NWR) pathways in humans are modulated by several cognitive factors. This study assesses how the predictability of a threat affects the biomechanical pattern of the withdrawal response, showing that distal and proximal muscles are differentially modulated by descending control.

OnabotulinumtoxinA Reduces Temporal Pain Processing at Spinal Level in Patients with Lower Limb Spasticity

Spasticity is a muscle tone disorder associated with different neurological conditions. Spasticity could be associated with pain, high disability, poor functional recovery, and reduced quality of life. Botulinum neurotoxin type A (BoNT-A) is considered a first-line treatment for spasticity and, more recently, it also represents a therapeutic option for various chronic pain conditions. In this open label study, we aim to evaluate the effect of the BoNT-A on the spinal nociception in patients affected by spasticity of the lower limbs with associated pain with predominantly neuropathic features. Ten patients with stroke, 10 with multiple sclerosis and 5 with spinal cord injury were enrolled in the study. They were tested with clinical scales (neuropathic pain scale inventory (NPSI), numerical rating scale (NRS), modified Ashworth scale (MAS) and with the nociceptive withdrawal reflex at lower limbs to explore the spinal temporal summation threshold at baseline and 30 day after BoNT-A injection. OnabotulinumtoxinA (50 to 200 units per site) was injected in the lower limb muscles according to the distribution of spasticity. No significant differences were found at baseline for neurophysiological features across groups. After the BoNT-A injection, we recorded a significant reduction in MAS and NRS scores. Regarding the neurophysiological parameters, we described a significant increase in the temporal summation threshold after the BoNT-A injection. Our data supports the hypothesis that peripherally injected OnabotulinumtoxinA modulates the excitability of spinal cord nociceptive pathways. This activity may take place irrespective of the effect of the drug on spasticity.

Botulinum toxin A modifies nociceptive withdrawal reflex in subacute stroke patients

OBJECTIVES

The 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.

METHODS

Fourteen 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.

RESULTS

Comparison 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.

CONCLUSION

Injection 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.