BOTULINUM TOXIN: FROM SPASTICITY RELIEVER TO A NEUROMOTOR RE-LEARNING TOOL

Agrin Influences Botulinum Neurotoxin A-Induced Nerve Sprouting via miR-144-agrin-MuSK Signaling

Botulinum neurotoxin (BoNT) has become a powerful therapeutic tool, and is extensively used in aesthetic medicine and in the treatment of neurological disorders. However, its duration of effect is limited, mainly owing to nerve sprouting. Inhibition of nerve sprouting to prolong the effective duration of BoNT is therefore of great clinical interest. However, appropriate interventional strategies to accomplish this are currently unavailable. In this study, we determined the role of the neurogenic regulator agrin in BoNT type A (BoNT/A)-induced nerve sprouting in a rat model. We then determined whether agrin could be used as an interventional target for prolonging the duration of effect of BoNT/A, and made a preliminary study of the upstream and downstream regulatory mechanisms by which agrin could influence the effective duration of BoNT/A. Our results showed that agrin was involved in the regulation of BoNT/A-induced nerve sprouting, and blocking of agrin function with anti-agrin antibody temporarily could delay muscle strength recovery and prolong the duration of BoNT/A effect. Moreover, agrin influenced the duration of BoNT/A effect by regulating downstream myogenic muscle-specific receptor tyrosine kinase (MuSK), and was simultaneously regulated by upstream miR-144. In conclusion, agrin could regulate BoNT/A-induced nerve sprouting through miR-144-agrin-MuSK signaling; it influences the effective duration of BoNT/A, and could find clinical application as an interventional target for prolonging the effect of BoNT/A.

Combined treatment of botulinumtoxin and robot-assisted rehabilitation therapy on poststroke, upper limb spasticity: A case report

RATIONALE

Spasticity is a major complication after stroke, and botulinumtoxin A (BoNT-A) injection is commonly used to manage focal spasticity. However, it is uncertain whether BoNT-A can improve voluntary motor control or activities of daily living function of paretic upper limbs. This study investigated whether BoNT-A injection combined with robot-assisted upper limb therapy improves voluntary motor control or functions of upper limbs after stroke.

PATIENT CONCERNS

Two subacute stroke patients were transferred to the Department of Rehabilitation.

DIAGNOSES

Patients demonstrated spasticity in the upper extremity on the affected side.

INTERVENTIONS

BoNT-A was injected into the paretic muscles of the shoulder, arm, and forearm of the 2 patients at the subacute stage. Conventional rehabilitation therapy and robot-assisted upper limb training were performed during the rehabilitation period.

OUTCOMES

Manual dexterity, grip strength, muscle tone, and activities of daily living function were improved after multidisciplinary rehabilitation treatment.

LESSONS

BoNT-A injection in combination with multidisciplinary rehabilitation treatment, including robot-assisted arm training, should be recommended for subacute spastic stroke patients to enhance appropriate motor recovery.

Spasticity, Motor Recovery, and Neural Plasticity after Stroke

Spasticity and weakness (spastic paresis) are the primary motor impairments after stroke and impose significant challenges for treatment and patient care. Spasticity emerges and disappears in the course of complete motor recovery. Spasticity and motor recovery are both related to neural plasticity after stroke. However, the relation between the two remains poorly understood among clinicians and researchers. Recovery of strength and motor function is mainly attributed to cortical plastic reorganization in the early recovery phase, while reticulospinal (RS) hyperexcitability as a result of maladaptive plasticity, is the most plausible mechanism for poststroke spasticity. It is important to differentiate and understand that motor recovery and spasticity have different underlying mechanisms. Facilitation and modulation of neural plasticity through rehabilitative strategies, such as early interventions with repetitive goal-oriented intensive therapy, appropriate non-invasive brain stimulation, and pharmacological agents, are the keys to promote motor recovery. Individualized rehabilitation protocols could be developed to utilize or avoid the maladaptive plasticity, such as RS hyperexcitability, in the course of motor recovery. Aggressive and appropriate spasticity management with botulinum toxin therapy is an example of how to create a transient plastic state of the neuromotor system that allows motor re-learning and recovery in chronic stages.

Placebo effects in a multiple sclerosis spasticity enriched clinical trial with the oromucosal cannabinoid spray (THC/CBD): dimension and possible causes

Regulatory authorities admit clinical studies with an initial enrichment phase to select patients that respond to treatment before randomization (Enriched Design Studies; EDSs). The trial period aims to prevent long-term drug exposure risks in patients with limited chances of improvement while optimizing costs. In EDSs for symptom control therapies providing early improvements and without a wash-out period, it is difficult to show further improvements and thus large therapeutic gains versus placebo. Moreover, in trials with cannabinoids, the therapeutic gains can be further biased in the postenrichment randomized phase because of carryover and other effects. The aims of the present review article are to examine the placebo effects in the enrichment and postenrichment phases of an EDS with Δ(9) -tetrahydrocannabinol and cannabidiol (THC/CBD) oromucosal spray in patients with multiple sclerosis (MS) spasticity and to discuss the possible causes of maintained efficacy after randomization in the placebo-allocated patients. The overall mean therapeutic gain of THC/CBD spray over placebo in resistant MS spasticity after 16 weeks can be estimated as a ~1.27-point improvement on the spasticity 0-10 Numerical Rating Scale (NRS; ~-20.1% of the baseline NRS score). We conclude that careful interpretation of the results of EDSs is required, especially when cannabinoid-based medications are being investigated.

Botulinum toxin injection for hypertonicity of the upper extremity within 12 weeks after stroke: a randomized controlled trial

BACKGROUND

Botulinum neurotoxin type A (BoNT-A) reduces upper-extremity poststroke spasticity when given 6 or more months after stroke. Effects on functional use of the arm and hand are less apparent.

OBJECTIVE

To determine the effect and safety of very early use of BoNT-A for patients with upper-limb spasticity.

METHODS

The Asia Botulinum Toxin-A Clinical Trial

DESIGN

ed for Early Post-stroke Spasticity (ABCDE-S; NCT00234546) was a multicenter, randomized, placebo-controlled trial conducted in patients recruited within 2 -12 weeks of first-ever stroke. Participants with a Modified Ashworth Scale (MAS) score of 1+ or above received BoNT-A (Dysport) 500 U or placebo to one or more wrist and elbow mover muscles, plus unstructured rehabilitation. The primary outcome was the MAS score in the most affected joint 4 weeks after first injection. Follow-up was 24 weeks.

RESULTS

A total of 163 patients were enrolled and assigned to placebo (n = 83) or BoNT-A (n = 80). Mean time since stroke was about 7 weeks. At 4 weeks postinjection, BoNT-A significantly improved MAS scores. Treatment effect-size estimates increased with higher baseline MAS scores from 0.45 (Q1) to 0.70 (Q3). MAS scores for all secondary end points improved with BoNT-A versus placebo at all time points (P < .0001, all visits). The Functional Motor Assessment Scale did not reveal clinically significant differences. No group differences in adverse events were found. Interpretation. BoNT-A 500 U can provide a sustained reduction in poststroke upper-limb spasticity when combined with rehabilitation in Asian patients who have mild-to-moderate hypertonicity and voluntary movement, within 2 -12 weeks of stroke. Functional use of the arm and hand was not affected.

Treatment-induced plasticity in cerebral palsy: a diffusion tensor imaging study

Diffusion tensor imaging is used as a measure of white-matter organization to probe mechanisms underlying clinical responses. Diffusion tensor imaging and clinical assessment in 8 patients with spastic quadriparesis (mean age, 6.13 years) was performed before and 6 months after therapy (botulinum injection, followed by physiotherapy). All patients were graded on the basis of gross motor function. Serial diffusion tensor imaging was also performed on 10 age/sex-matched controls at baseline and after 6 months. Regions of interests were placed on corticospinal tracts at different levels (i.e., corona radiata, posterior limb of internal capsule, midbrain, pons, and upper medulla) and on other major white-matter tracts, in both patients and controls. A significant increase in fractional anisotropy was evident in corticospinal tracts at the level of the posterior limb of the internal capsule and periventricular white matter of the temporal lobe, relative to baseline values in the patient group. Gross motor function classification system grades improved in all patients during follow-up relative to baseline values. The increase in fractional anisotropy in corticospinal tracts, along with improved clinical motor scores, suggests plasticity of the central motor pathway after combined therapy.

The nature of hand motor impairment after stroke and its treatment

Hand motor impairments may be viewed as 1) a deficit in motor execution, resulting from weakness, spasticity, and abnormal muscle synergies, and/or 2) a deficit in higher-order processes, such as motor planning and motor learning, which lead to poorly formed sensorimotor associations that lead to impaired motor control. Although weakness and spasticity impede motor execution, strengthening and tone reduction represent simplistic solutions to the deficit in motor control after stroke. Deficits in hand motor control are better appreciated by examining the coordination of fingertip forces and movements during natural movements, and suggest that impairments in motor learning and planning are fundamental impediments to motor recovery following stroke. However, despite an explosion in the number of therapeutic protocols based on the principles of motor learning, little is known about the types of motor learning impairment that occur after stroke and how lesion location may influence motor relearning.

Relearning toward motor recovery in stroke, spinal cord injury, and cerebral palsy: a cognitive neural systems perspective

In stroke, spinal cord injury, and cerebral palsy there is denervation of target neuron centers, which are self-organizing maps (SOMs) within the neuraxis. Compensatory reinnervation occurs within those SOMs by acquiring synaptic sprouts from whatever neurons in the neighborhood. Such reorganizations are more often maladaptive than beneficial. Motor recovery, if any appears, is incomplete and compromised. Cognitive systems studies indicate that motor paralysis is due to loss of learning <--> recall balance in those compensated SOMs, which had been locked into a stability <--> plasticity dilemma. Treatment/rehabilitation should aim therefore to first restore this learning related balance. The use of botulinum toxin as a neuromotor relearning tool to improve motor recovery is discussed.