Botulinum toxin type A in chronic migraine

The use of botulinum toxin type A continues to be investigated by the US FDA for potential use in the treatment of headache. As part of this process there has been extensive research conducted by individual study sites as well as multicenter trials. To date, the majority of the focus has been on migraine headache as well as on tension-type headache. The results of these studies have been mixed. A variety of issues may contribute to the mixed results, including difference in the dose of toxin used, the number of injection sites utilized, the treatment paradigm itself, confounding medications, high and prolonged placebo response, as well as patient selection issues. Currently, the focus on botulinum toxin type A is on those patients who have chronic daily headache with a migraine component to their clinical picture. The results of two large trials in this population produced positive findings, especially when consideration is given to the a priori additional analyses of this complex patient population. The results of these studies have allowed a more focused program to be undertaken in the Phase III evaluation. At the same time, additional work has been performed to understand the mechanism by which botulinum toxin type A may work to alleviate migraine. This work may contribute substantially to improving outcomes with botulinum toxin type A. Characterization of the mechanism of action in pain may be crucial to outcomes because many issues are related to central sensitization.     

The structure and mode of action of different botulinum toxins

The seven serotypes (A–G) of botulinum neurotoxin (BoNT) are proteins produced by Clostridium botulinum and have multifunctional abilities: (i) they target cholinergic nerve endings via binding to ecto-acceptors (ii) they undergo endocytosis/translocation and (iii) their light chains act intraneuronally to block acetylcholine release. The fundamental process of quantal transmitter release occurs by Ca²⁺-regulated exocytosis involving sensitive factor attachment protein-25 (SNAP-25), syntaxin and synaptobrevin. Proteolytic cleavage by BoNT-A of nine amino acids from the C-terminal of SNAP-25 disables its function, causing prolonged muscle weakness. This unique combination of activities underlies the effectiveness of BoNT-A haemagglutinin complex in treating human conditions resulting from hyperactivity at peripheral cholinergic nerve endings. In vivo imaging and immunomicroscopy of murine muscles injected with type A toxin revealed that the extended duration of action results from the longevity of its protease, persistence of the cleaved SNAP-25 and a protracted time course for the remodelling of treated nerve–muscle synapses. In addition, an application in pain management has been indicated by the ability of BoNT to inhibit neuropeptide release from nociceptors, thereby blocking central and peripheral pain sensitization processes. The widespread cellular distribution of SNAP-25 and the diversity of the toxin's neuronal acceptors are being exploited for other therapeutic applications.     

Painful limbs/moving extremities

Painful limbs/moving extremities (PLME) is a disorder characterized by spontaneous, complex, slow (1–2 Hz) involuntary toe or finger movements. The movements that can be bilateral or unilateral are usually accompanied by pain in the affected limbs. Painless variants are less common. PLME has been associated with peripheral and central nervous system disease although idiopathic cases have been reported. Its etiopathogenesis is unknown and treatment approaches remain largely empirical. Nerve blocks and botulinum toxin type A injections as well as oral medication have had some measure of success. Current theories suggest that central oscillator(s) at the spinal or supraspinal levels may be involved. Future research in PLME should include prospective electrophysiological and functional imaging studies as well as clinical trials with botulinum toxin injections and oral pharmacological agents.     

Botulinum-Toxin A in der Therapie von Kopfschmerzerkrankungen und perikranialen Schmerzsyndromen

For 20 years botulinum toxin A has been used for the treatment of a variety of disorders characterised by pathologically increased muscle contraction. Recently, treatment of tension headache, migraine, cluster headache, and myofascial pain syndromes of neck, shoulder girdle, and back with botulinum toxin A has become a rapidly expanding new field of research. Several modes of action are discussed for these indications. The blockade of cholinergic innervation reduces muscular hyperactivity for 3 to 6 months. Degenerative changes in the musculoskeletal system of the head and neck are prevented. Nociceptive afferences and blood vessels of the pericranial muscles are decompressed and muscular trigger points and tender points are resolved. The normalisation of muscle spindle activity leads to a normalisation of muscle tone and central control mechanisms of muscle activity. Oromandibular dysfunction is eliminated and muscular stress removed. However, the effect of botulinum toxin A cannot be explained by muscular actions only. Its retrograde uptake into the central nervous system modulates the expression of substance P and enkephalins in the spinal cord and nucleus raphe. Recent findings suggest an inhibition of sterile inflammation which may lead to a blockade of the neurogenic inflammation believed to be the pathophysiological substrate of primary headache disorders. The efficacy of botulinum toxin A in the treatment of pain disorders is being investigated in several studies at the moment. The results and experiences obtained so far present new alternatives in the treatment of chronic pain disorders. The practical use of botulinum toxin A is demonstrated.     

The structure and mode of action of different botulinum toxins

The seven serotypes (A–G) of botulinum neurotoxin (BoNT) are proteins produced by Clostridium botulinum and have multifunctional abilities: (i) they target cholinergic nerve endings via binding to ecto‐acceptors (ii) they undergo endocytosis/translocation and (iii) their light chains act intraneuronally to block acetylcholine release. The fundamental process of quantal transmitter release occurs by Ca²⁺‐regulated exocytosis involving sensitive factor attachment protein‐25 (SNAP‐25), syntaxin and synaptobrevin. Proteolytic cleavage by BoNT‐A of nine amino acids from the C‐terminal of SNAP‐25 disables its function, causing prolonged muscle weakness. This unique combination of activities underlies the effectiveness of BoNT‐A haemagglutinin complex in treating human conditions resulting from hyperactivity at peripheral cholinergic nerve endings. In vivo imaging and immunomicroscopy of murine muscles injected with type A toxin revealed that the extended duration of action results from the longevity of its protease, persistence of the cleaved SNAP‐25 and a protracted time course for the remodelling of treated nerve–muscle synapses. In addition, an application in pain management has been indicated by the ability of BoNT to inhibit neuropeptide release from nociceptors, thereby blocking central and peripheral pain sensitization processes. The widespread cellular distribution of SNAP‐25 and the diversity of the toxin's neuronal acceptors are being exploited for other therapeutic applications.     

Experience with botulinum toxin type A in medically intractable pediatric chronic daily headache

In adults, botulinum toxin type A has been studied as a potentially effective treatment for chronic daily headache. For pediatric chronic daily headache, the literature evaluating efficacy of botulinum toxin type A is sparse, with no studies assessing tolerability. The purpose of this retrospective case series study was to assess tolerability and efficacy of botulinum toxin type A in the treatment of pediatric chronic daily headache. The series comprises 10 patients (ages 11-17 years) who received a standard 100-unit dose of onabotulinumtoxinA (trade name, Botox) for refractory chronic daily headache. Attention was given to therapeutic history, efficacy, and tolerability. The patients had attempted an average of 8.0 ± 2.40 S.D. therapies prior to botulinum toxin type A. Most patients reported adverse events from at least one of these prior medications. With botulinum toxin type A, four patients (40%) reported subjective but clinically meaningful relief, consisting of a decrease in headache intensity, and two patients additionally noted a decrease in headache frequency. The four responders noted improvements in quality of life. Three patients experienced minor adverse events from botulinum toxin type A. This case series suggests that botulinum toxin type A can be well tolerated and may be a useful therapeutic in pediatric patients with highly medically intractable chronic daily headache.     

Botulinumtoxin A in der Kopfschmerztherapie

In recent years botulinum toxin type A has been used increasingly more in the treatment of specific headache disorders. Especially regarding chronic migraine with and without combined medication overuse, convincing randomized studies have proven the efficacy of this treatment option and have led to approval for this indication. Regarding other headache entities, such as episodic migraine, tension-type headache, trigeminal autonomic cephalalgia (TAC), neuralgic, neuropathic and myofascial pain, currently available scientific data on the efficacy of botulinum toxin type A are scarce and often ambiguous. The exact underlying mechanisms of the influence of botulinum toxin type A on the pathophysiology of headache are not completely clear but an influence on the release of calcitonin gene-related peptide (CGRP) seems to play a crucial role. This article summarizes the most important studies as well as experiences of treatment with botulinum toxin type A regarding different headache entities.     

Association of antinociceptive action of botulinum toxin type A with GABA-A receptor

The mechanism of botulinum toxin type A (BTX-A) antinociceptive action in the central nervous system is little known. The potential interaction between BTX-A and GABAergic system has not been investigated previously. In the present study, we demonstrate prevention of BTX-A antinociceptive effect on formalin-induced inflammatory pain and partial sciatic nerve transection-induced mechanical allodynia by GABA-A antagonist bicuculline, thus suggesting association of the GABA-A receptors and antinociceptive action of BTX-A.     

Myoclonus of peripheral origin: Two case reports

The concept of peripheral myoclonus is not yet fully accepted by the medical community because of the difficulty in establishing a cause‐and‐effect relationship between trauma and subsequent movement disorders. Here, we report two cases of patients suffering from peripheral myoclonus after nerve injury. The first patient experienced myoclonus of the 4th dorsal interosseous muscle several days after trauma to the elbow. The second patient presented myoclonus of the arm stump (combined with phantom‐limb pain) 1 year after amputation. In both cases, central nervous system function (spine and brain imaging, somesthetic evoked potentials, EEG back‐averaging) was normal. For the second patient, local infiltration of xylocaine and botulinum toxin into the stump scar rapidly stopped myoclonus and pain. Nerve injury induces ephaptic transmission and ectopic excitation. The physiopathological mechanisms of this type of myoclonus involve a peripheral generator that induces central (spinal) generator activity. © 2008 Movement Disorder Society     

Beneficial effects of botulinum toxin type a for patients with painful tic convulsif

Botulinum toxin is a well-known therapy for patients with diverse movement disorders. Its application has been extended to other disorders. Here, we document the case of a 70-year-old man with hemifacial spasm associated to trigeminal neuralgia secondary to an ectatic basilar artery. He was treated with botulinum toxin type A, 2.5 mouse units over five sites at the orbicularis oculi and one over the buccinator muscle. After botulinum toxin injections, relief was gained not only from twitching but also from pain. When the effects of the toxin vanished, spasms and pain recurred. Further infiltrations were given every 12 weeks following the same response pattern. This observation further validates the increasing role of botulinum toxin in pain management.     

Botulinum toxin A and chronic low back pain: a randomized, double-blind study

OBJECTIVES: To investigate the efficacy of botulinum toxin A in chronic low back pain and associated disabilities. METHODS: Thirty-one consecutive patients with chronic low back pain who met the inclusion criteria were studied: 15 received 200 units of botulinum toxin type A, 40 units/site at five lumbar paravertebral levels on the side of maximum discomfort, and 16 received normal saline. Each patient's baseline level of pain and degree of disability was documented using the visual analogue scale (VAS) and the Oswestry Low Back Pain Questionnaire (OLBPQ). The authors reevaluated the patients at 3 and 8 weeks (visual analogue scale) and at 8 weeks (OLBPQ). RESULTS: At 3 weeks, 11 of 15 patients who received botulinum toxin (73.3%) had >50% pain relief vs four of 16 (25%) in the saline group (p = 0.012). At 8 weeks, nine of 15 (60%) in the botulinum toxin group and two of 16 (12.5%) in the saline group had relief (p = 0.009). Repeat OLBPQ at 8 weeks showed improvement in 10 of 15 (66.7%) in the botulinum toxin group vs three of 16 (18.8%) in the saline group (p = 0.011). No patient experienced side effects. CONCLUSION: Paravertebral administration of botulinum toxin A in patients with chronic low back pain relieved pain and improved function at 3 and 8 weeks after treatment.     

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.     

Mechanisms of pain in peripheral neuropathy

Over the last few years, the mechanisms of pain due to peripheral nerve injury have been the subject of extensive clinical and fundamental investigation. Several types of peripheral mechanisms have been described in animal models of peripheral nerve injury. Abnormal (ectopic) neuronal activity has been reported in primary afferents and in the dorsal root ganglion, and appears related to dysregulation of the synthesis and/or the functioning of sodium channels (notably the tetrodotoxin-resistant channel). Fiber interactions (ephaptic or cross-excitation), nociceptor sensitization and sympathetic sensory coupling may also be involved in some cases. Peripheral nerve lesions can also induce central changes; this has essentially been investigated at the spinal cord level in animals. Three major types of modifications could induce a pathologic activation of central nociceptive neurons: modification of the moduhtory controls of the transmission of nociceptive messages; anatomic reorganization (neuro-plasticity) of the central nociceptive neurons, and thus their pathologic activation; and central sensitization (hyperexcitability) of nociceptive neurons to produce modifications of their electrophysiologic properties. Central sensitization probably depends critically on intracellular changes induced by the activation of N methyl-D-aspartate (NMDA) receptors by excitatory amino acids released by primary afferents. Due to the multiplicity of mechanisms, it is unlikely that neuropathic pain corresponds to a unique entity. Each of the painful symptoms may correspond to distinct mechanisms and thus respond to specific treatments.     

Evidence based medicine on the use of botulinum toxin for headache disorders

Botulinum toxin blocks the release of acetylcholine from motor nerve terminals and other cholinergic synapses. In animal studies botulinum toxin also reduces the release of neuropeptides involved in pain perception. The implications of these observations are not clear. Based on the personal experiences of headache therapists, botulinum toxin injections have been studied in patients with primary headaches, namely tension-type headache (TTH), chronic migraine (CM) and chronic daily headache (CDH). So far, the results of randomized, double-blind, placebo controlled trials on botulinum toxin in a total of 1117 patients with CDH, 1495 patients with CM, and 533 patients with TTH have been published. Botulinum toxin and placebo injections have been equally effective in these studies. In some of the studies, the magnitude of this effect was similar to that of established oral pharmacotherapy. This finding may help to explain the enthusiasm that followed the first open-label use of botulinum toxin in patients with headache. However, research is continuing to determine the efficacy of botulinum toxin in certain subgroups of patients with CM or CDH.     

Acrylamide inhibits nerve sprouting induced by botulinum toxin type A

Botulinum toxin type A is a potent muscle relaxant that blocks the transmission and release of acetylcholine at the neuromuscular junction. Intramuscular injection of botulinum toxin type A has served as an effective and safe therapy for strabismus and focal dystonia. However, muscular weakness is temporary and after 3–4 months, muscle strength usually recovers because functional recovery is mediated by nerve sprouting and reconstruction of the neuromuscular junction. Acrylamide may produce neurotoxic substances that cause retrograde necrotizing neuropathy and inhibit nerve sprouting caused by botulinum toxin type A. This study investigated whether acrylamide inhibits nerve sprouting after intramuscular injection of botulinum toxin type A. A tibial nerve sprouting model was established through local injection of botulinum toxin type A into the right gastrocnemius muscle of Sprague-Dawley rats. Following intramuscular injection, rats were given intraperitoneal injection of 3% acrylamide every 3 days for 21 days. Nerve sprouting appeared 2 weeks after intramuscular injection of botulinum toxin type A and single-fiber electromyography revealed abnormal conduction at the neuromuscular junction 1 week after intramuscular injection of botulinum toxin type A. Following intraperitoneal injection of acrylamide, the peak muscle fiber density decreased. Electromyography jitter value were restored to normal levels 6 weeks after injection. This indicates that the maximal decrease in fiber density and the time at which functional conduction of neuromuscular junction was restored were delayed. Additionally, the increase in tibial nerve fibers was reduced. Acrylamide inhibits nerve sprouting caused by botulinum toxin type A and may be used to prolong the clinical dosage of botulinum toxin type A.     

Expanding use of botulinum toxin

Botulinum toxin type A (BTX-A) is best known to neurologists as a treatment for neuromuscular conditions such as dystonias and spasticity and has recently been publicized for the management of facial wrinkles. The property that makes botulinum toxin type A useful for these various conditions is the inhibition of acetylcholine release at the neuromuscular junction. Although botulinum toxin types A and B (BTX-A and BTX-B) continue to find new uses in neuromuscular conditions involving the somatic nervous system, it has also been recognized that the effects of these medications are not confined to cholinergic neurons at the neuromuscular junction. Acceptors for BTX-A and BTX-B are also found on autonomic nerve terminals, where they inhibit acetylcholine release at glands and smooth muscle. This observation led to trials of botulinum neurotoxins in various conditions involving autonomic innervation. The article reviews the emerging use of botulinum neurotoxins in these and selected other conditions, including sialorrhea, primary focal hyperhidrosis, pathological pain and primary headache disorders that may be of interest to neurologists and related specialists.     

Botulinum toxin in migraine prophylaxis

Migraine is a chronic headache disorder manifesting in attacks lasting 4-72 hours. Characteristics of headache are unilateral location, pulsating quality, moderate or severe intensity, aggravation by routine physical activity, and association with nausea, photophobia and phonophobia. The migraine aura is a complex of neurological symptoms, which occurs just before or at the onset of migraine headache. Botulinum toxin A represents a completely new option for patients with chronic pain conditions. Numerous retrospective open-label chart reviews and 4 double-blind, placebo-controlled studies have demonstrated that botulinum toxin type A is significantly effective in migraine prophylaxis and reduces the frequency, severity, and disability associated with migraine headaches. Studies have generally reported a good and consistent efficacy. The differential therapeutic use of botulinum toxin appears to be worth attempting in migraine patients with the following characteristic features: (1) Muscular stress as migraine trigger, e. g., in craniocervical dystonia, pericranial painful muscular trigger points or tender points, oromandibular dysfunction, (2) concurrent chronic tension-type headache with the aggravating factors of muscular stress or oromandibular dysfunction, (3) chronic migraine with frequent migraine attacks on more than 15 days per month for longer than 3 months and if other therapeutic options have been either ineffective or have not been tolerated. The use of the agent does not cause CNS side effects. Migraine patients in particular, often suffer greatly, as a result of the adverse effects of the drugs used, from fatigue, dizziness, reduced concentration, loss of appetite, weight gain, hair loss and changes in libido. These side effects are not known in association with botulinum toxin A. To date, neither organic damage nor allergic complications have been reported. Thus, both the tolerability and the safety of this therapeutic measure are high. The mode of action by which botulinum toxin is effective in migraine prophylaxis is not fully understood and is under investigation. Currently, a number of other randomized, placebo-controlled, clinical trials are being conducted to evaluate the efficacy, optimal dosing, and side-effect profile of botulinum toxin type A in the prophylaxis of migraine and other headache entities.     

Secretome of human adipose-derived mesenchymal stem cell relieves pain and neuroinflammation independently of the route of administration in experimental osteoarthritis

ObjectiveTreatment of pain associated with osteoarthritis (OA) is unsatisfactory and innovative approaches are needed. The secretome from human adipose-derived mesenchymal stem cells (hASC-Conditioned Medium, CM) has been successfully used to relieve painful symptoms in models of chronic pain. The aim of this study was to explore the efficacy of the hASC-CM to control pain and neuroinflammation in an animal model of OA.MethodsOA was induced in mice by intra-articular monosodium-iodoacetate (MIA) injection. Thermal hyperalgesia and mechanical allodynia were assessed. Once hypersensitivity was established (7 days after MIA), hASC-CM was injected by IA, IPL and IV route and its effect monitored over time. Neuroinflammation in nerve, dorsal root ganglia and spinal cord was evaluated measuring proinflammatory markers and mediators by RT-qPCR. Protein content analysis of secretome by Mass Spectrometry was performed.ResultsA single injection with hASC-CM induced a fast and long lasting antihyperalgesic and antiallodynic effect. The IV route of administration appeared to be the most efficacious although all the treatments were effective. The effect on pain correlated with the ability of hASC-CM to reduce the neuroinflammatory condition in both the peripheral and central nervous system. Furthermore, the secretome analysis revealed 101 factors associated with immune regulation.ConclusionWe suggest that hASC-CM is a valid treatment option for controlling OA-related hypersensitivity, exerting a rapid and long lasting pain relief. The mechanisms underpinning its effects are likely linked to the positive modulation of neuroinflammation in peripheral and central nervous system that sustains peripheral and central sensitization.     

Antibody-induced failure of botulinum toxin type B therapy in de novo patients

Botulinum toxin type B (BT-B) therapy failure due to formation of botulinum toxin type B antibodies (BT-B-AB) has only been reported in patients with botulinum toxin type A antibodies (BT-A-AB). We are reporting BT-B-AB-induced therapy failure in 2 patients with no previous exposure to botulinum toxin. In patient 1 complete therapy failure occurred after a single exposure to 14,400 mouse units (MU) BT-B (NeuroBloc). The mouse diaphragm assay (MDA) revealed a BT-B-AB titre in excess of 10 mU/ml. Doubling the BT-B dose did not elicit any effects. Application of 360 MU BT-A (Botox) produced the original therapeutic effect, but the second BT-A application was followed by partial and the third by complete therapy failure. Doubling the BT-A dose did not elicit any effects. MDA testing showed a BT-A-AB titre in excess of 10 mU/ml. In patient 2 a single exposure to 7,200 MU BT-B lead to a complete therapy failure. MDA testing revealed a BT-B-AB titre in excess of 10 mU/ml. Doubling the BT-B dose did not elicit any effects. Application of 180 MU BT-A (Botox) produced the original response on 3 consecutive applications. Antibody formation can occur after a single exposure to botulinum toxin. However, this is highly unusual. Since therapy failure occurred after the first-ever botulinum toxin exposure, short intervals between injections and use of booster injections can be excluded as causes for BT-B-AB formation in both patients. A more likely cause may be the substantially higher amount of antigenic protein administered in BT-B therapy compared to BT-A therapy. Further studies are necessary to compare the incidence of antibody formation in BT-B and BT-A therapy.     

Alteration of central motor excitability in a patient with hemimasticatory spasm after treatment with botulinum toxin injections.

Hemimasticatory spasm (HMS) is a condition characterized by paroxysmal involuntary contraction of masticatory muscles. We performed an electrophysiological investigation of a single patient with HMS to identify any pathophysiological changes associated with the condition. We identified a delayed M wave and jaw jerk on the affected side and an absent masseteric silent period during spasm. Botulinum toxin injections successfully treated the clinical symptoms and resulted in a significant reduction in the excitability of the blink reflex recovery cycle. These data suggest that HMS may be due to ectopic activity in the motor portion of the trigeminal nerve that is capable of inducing changes in the excitability of central reflex pathways. These changes can be altered by successful treatment with botulinum toxin.