Botulinum toxin type A in post-stroke lower limb spasticity: a multicenter, double-blind, placebo-controlled trial. J Neurol. 2010;257:1330-1337. [PMID: 20358216 PMCID: PMC2910313 DOI: 10.1007/s00415-010-5526-3]

Clinical uses of botulinum neurotoxins: current indications, limitations and future developments

Botulinum neurotoxins (BoNTs) cause flaccid paralysis by interfering with vesicle fusion and neurotransmitter release in the neuronal cells. BoNTs are the most widely used therapeutic proteins. BoNT/A was approved by the U.S. FDA to treat strabismus, blepharospam, and hemificial spasm as early as 1989 and then for treatment of cervical dystonia, glabellar facial lines, axillary hyperhidrosis, chronic migraine and for cosmetic use. Due to its high efficacy, longevity of action and satisfactory safety profile, it has been used empirically in a variety of ophthalmological, gastrointestinal, urological, orthopedic, dermatological, secretory, and painful disorders. Currently available BoNT therapies are limited to neuronal indications with the requirement of periodic injections resulting in immune-resistance for some indications. Recent understanding of the structure-function relationship of BoNTs prompted the engineering of novel BoNTs to extend therapeutic interventions in non-neuronal systems and to overcome the immune-resistance issue. Much research still needs to be done to improve and extend the medical uses of BoNTs.

Beyond muscular effects: depression of spinal recurrent inhibition after botulinum neurotoxin A

The natural target of the botulinum neurototoxin type A (BoNT-A) is the neuromuscular junction. When injected into a muscle, BoNT-A is internalized by motoneurone terminals where it functions as an endopeptidase, cleaving protein components of the synaptic machinery responsible for vesicle docking and exocytosis. As a result, BoNT-A induces a characteristic flaccid paralysis of the affected muscle. In animal models, BoNT-A applied in the periphery can also influence central activity via retrograde transport and transcytosis. An analogous direct central effect in humans is still debated. The present study was designed to address whether BoNT-A modifies the activity of the spinal recurrent inhibitory pathways, when injected at muscular level, in humans. To avoid methodological bias, the recurrent inhibition from an injected muscle (soleus) was investigated on an untreated muscle (quadriceps), and stimulation parameters (producing recurrent inhibition) were monitored on a third non-injected muscle but innervated by the same nerve as the soleus (flexor digitorum brevis). The experiments were performed on 14 post-stroke patients exhibiting spasticity in ankle plantarflexors, candidates for BoNT-A. One month after BoNT-A, the level of recurrent inhibition was depressed. It is suggested that the depression of recurrent inhibition was induced by BoNT-A, injected peripherally, through axonal transport and blockade of the cholinergic synapse between motoneurone recurrent collaterals and Renshaw cells.

Botulinum toxin type A combined with neurodynamic mobilization for upper limb spasticity after stroke: a case report

OBJECTIVE

The purpose of this study is to report a case in which combinatory therapy of botulinum toxin type A (BoNT-A) and neurodynamic mobilization (NM) was used as treatment for a patient with severe upper limb spasticity and pain after stroke.

CLINICAL FEATURES

A 76-year-old male patient had spastic muscles in the upper limb 10 months after an ischemic stroke.

INTERVENTION AND OUTCOME

The patient underwent combined treatment with BoNT-A and NM of the upper limb in 6 monthly applications. Evaluation was performed pretreatment, 3 months after the first injection, 3 months after the second injection, and at a follow-up session 9 months after starting the treatment. The following outcomes were measured: pain by using a numeric rating scale, spasticity by the Modified Ashworth Scale for Grading Spasticity, acceptance and emotional reaction to the treatment by the Hospital Anxiety and Depression Scale, and functionality by ranges of motion. The patient improved in all outcomes after treatment, and results were maintained during the follow-up sessions.

CONCLUSION

The combined NM and BoNT-A treatment appeared to decrease pain and improve joint ranges of motion during treatment for this patient. The patient showed decreased anxiety and depression during and after the treatment.

New and emerging indications of botulinum toxin therapy

Botulinum neurotoxin (BoNT) is composed of the heavy chain with the receptor-binding site and the translocation domain and the light chain with endopeptidase activity that cleaves the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex, an essential molecule for membrane fusion. Its extraordinarily high toxicity depends on the affinity of the receptor-binding site to the receptor located inside the synaptosome. The membrane fusion mechanism is important not only in neurotransmitter release at the nerve terminals but also in the expression of pain receptors on the cell surface. Based on these mechanisms, BoNT is increasingly used for varieties of conditions including cosmetic uses, muscle hyperactivity, hyperhydrosis, pain, overactive bladder and epilepsy. It will become a major arm of neuromodulating treatments for neurological diseases. A part of this toxin, such as the heavy chain, may become a novel drug-delivery system for neurodegenerative diseases.

A prospective, multicentre, randomized, double-blind, placebo-controlled trial of onabotulinumtoxinA to treat plantarflexor/invertor overactivity after stroke

OBJECTIVE

To examine the safety and efficacy of onabotulinumtoxinA (Botox) for plantarflexor overactivity following stroke.

DESIGN

Double-blind randomized controlled trial, open-label extension phase.

SETTING

Neurology rehabilitation facilities.

SUBJECTS

Eighty-five subjects with lower limb hypertonia received 200 U (n = 28) or 300 U (n = 28) of onabotulinumtoxinA or saline (n = 29) injection.

PRIMARY MEASURES

Plantarflexor Ashworth scores at 12 weeks post injection and adverse events. Secondary measures: self-reported spasm frequency and pain, physician rating of hypertonia severity, gait quality and active dorsiflexion.

RESULTS

Differences were not seen between onabotulinumtoxinA groups; hence data were pooled. Incidence of adverse events was not different between groups (P = 0.61). Reduction in hypertonia was not different between groups at 12 weeks (P = 0.53); however for subjects with Ashworth scores of >3 at baseline, 14/31 in the onabotulinumtoxinA group demonstrated a reduction of >1 grade versus 1/17 receiving placebo injection (P = 0.01). Overall, onabotulinumtoxinA-injected subjects demonstrated significantly greater improvement in spasm frequency (22/54 versus 4/29, P = 0.01), pain reduction (8/54 versus 1/29, P = 0.02), active dorsiflexion (8/54 versus 1/29 P = 0.03) and gait quality (17/54 versus 6/29, P = 0.02) than controls. In the open-label phase, a second onabotulinumtoxinA injection was associated with greater hypertonia reduction (P = 0.005) and gait quality (P = 0.002) compared with single injection.

CONCLUSIONS

OnabotulinumtoxinA injection for ankle flexor overactivity after stroke was safe and well tolerated but did not alter local spasticity at 12 weeks; it did reduce spasms and improve gait quality. There were no detectable differences between higher and lower doses. A second injection may be associated with greater change.

Therapeutic use of botulinum toxin in neurorehabilitation

The botulinum toxins (BTX), type A and type B by blocking vesicle acetylcholine release at neuro-muscular and neuro-secretory junctions can result efficacious therapeutic agents for the treatment of numerous disorders in patients requiring neuro-rehabilitative intervention. Its use for the reduction of focal spasticity following stroke, brain injury, and cerebral palsy is provided. Although the reduction of spasticity is widely demonstrated with BTX type A injection, its impact on the improvement of dexterity and functional outcome remains controversial. The use of BTX for the rehabilitation of children with obstetrical brachial plexus palsy and in treating sialorrhea which can complicate the course of some severe neurological diseases such as amyotrophic lateral sclerosis and Parkinson's disease is also addressed. Adverse events and neutralizing antibodies formation after repeated BTX injections can occur. Since impaired neurological persons can have complex disabling feature, BTX treatment should be viewed as adjunct measure to other rehabilitative strategies that are based on the individual's residual ability and competence and targeted to achieve the best functional recovery. BTX therapy has high cost and transient effect, but its benefits outweigh these disadvantages. Future studies must clarify if this agent alone or adjunctive to other rehabilitative procedures works best on functional outcome.

An update on the neurologic applications of botulinum toxins

Initially used to treat strabismus in the 1970s, botulinum toxin now has more than a hundred possible medical applications. Its utility in neurologic conditions has largely involved treating movement disorders (particularly dystonia and conditions with muscle hyperactivity), although practically any hyperkinetic movement disorder may be relieved by botulinum toxin, including hemifacial spasm, tremor, tics, myoclonus, and spasticity. Although initially thought to inhibit acetylcholine release only at the neuromuscular junction, botulinum toxins are now recognized to inhibit acetylcholine release at autonomic cholinergic nerve terminals, as well as peripheral release of neurotransmitters involved in pain regulation. Thus, their use in neurology has been expanded to include headache and other pain syndromes, as well as hypersecretory disorders. This article highlights some of the common neurologic conditions currently improved by botulinum toxins and reviews the scientific evidence from research studies and clinical experience with these conditions.