Time course analysis of the effects of botulinum neurotoxin type A on pain and vasomotor responses evoked by glutamate injection into human temporalis muscles. Toxins (Basel). 2014;6:592-607. [PMID: 24517906 PMCID: PMC3942753 DOI: 10.3390/toxins6020592]

Pain, disability, and quality of life in participants after concurrent onabotulinumtoxinA treatment of upper and lower limb spasticity: Observational results from the ASPIRE study

INTRODUCTION

Upper and lower limb spasticity is commonly associated with central nervous system disorders including stroke, traumatic brain injury, multiple sclerosis, cerebral palsy, and spinal cord injury, but little is known about the concurrent treatment of upper and lower limb spasticity with botulinum toxins.

OBJECTIVE

To evaluate onabotulinumtoxinA (onabotA) utilization and to determine if concurrent onabotA treatment of the upper and lower limbs has supported improvements in participants with spasticity.

DESIGN

Sub-analysis of a 2-year, international, prospective, observational registry (ASPIRE, NCT01930786).

SETTING

International clinic sites (54).

PARTICIPANTS

Adult spasticity participants across etiologies, who received ≥1 concurrent onabotA treatment of the upper and lower limbs during the study.

INTERVENTION

Participants were treated with onabotA at the clinician's discretion.

OUTCOMES

Baseline characteristics and outcomes of disability (Disability Assessment Scale [DAS]), pain (Numeric Pain Rating Scale [NPRS]), participant satisfaction, physician satisfaction, and quality of life (QoL; Spasticity Impact Assessment [SIA]) were evaluated. Adverse events were monitored throughout the study.

RESULTS

Of 744 participants enrolled, 730 received ≥1 dose of onabotA; 275 participants received treatment with onabotA in both upper and lower limbs during ≥1 session; 39.3% of participants were naïve to onabotA for spasticity. The mean (SD) total dose per treatment session ranged from 421.2 (195.3) to 499.6 (188.6) U. The most common baseline upper limb presentation was clenched fist (n = 194, 70.5%); lower limb was equinovarus foot (n = 219, 66.9%). High physician and participant satisfaction and improvements in pain, disability and QoL were reported after most treatments. Nine participants (3.3%) reported nine treatment-related adverse events; two participants (0.7%) reported three serious treatment-related severe adverse events. No new safety signals were identified.

CONCLUSION

More than a third of enrolled participants received at least one concurrent onabotA treatment of the upper and lower limbs, with reduced pain, disability, and improved QoL after treatment, consistent with the established safety profile of onabotA for the treatment of spasticity.

Clinical efficacy of escitalopram combined with botulinum toxin A in patients with generalized anxiety disorder and comorbid headache

BACKGROUND

Generalized anxiety disorder (GAD) is a common mental disorder that happens comorbidly with other diseases. Headache is a common anxiety comorbidity. Previous reports have shown that the selection of therapeutic drugs for GAD patients and comorbid headache is challenging. Therefore, our study aimed to investigate the clinical efficacy of escitalopram combined with botulinum toxin A (BoNT/A) in patients with GAD and comorbid headache and seek an alternative treatment strategy for the comorbidity of GAD and headache.

METHODS

A prospective, randomized controlled, double-blind study was performed. The eligible GAD patients with comorbid headache were randomly assigned to the BoNT/A group and the placebo group. All the patients were given oral escitalopram therapy (10-20 mg/day) for the whole duration of the study. The BoNT/A group was given local injections of BoNT/A (50 U per person), whereas the placebo group was given local saline (0.9% NaCl) injections at the beginning and 3 months after the experiments. All participants were followed up for 6 months and relevant information was collected at months 0, 1, 2, 3, and 6. Primary outcomes included the following: (1) the Generalized Anxiety Disorder 7 (GAD-7); (2) the Self-rating Anxiety Scale (SAS); (3) the Hamilton Anxiety Rating Scales (HAMA); (4) days with headache per month; (5) visual analogue scale (VAS).

RESULTS

A total of 101 patients (the sex ratio of female to male: 3.39:1) were finally included. Compared with the placebo group, the BoNT/A group showed a significant decrease in GAD-7 scores, SAS scores, HAMA scores, days with headache per month, and VAS scores at months 1, 2, 3, and 6 of follow-up (all p < 0.05). The average time to complete remission of anxiety symptoms (HAMA< 7 points) in the BoNT/A group was less than the placebo group (2 months vs. 3 months). At the same time, the results of the survival analysis showed a clear beneficial effect of BoNT/A relative to placebo on the time to remission of anxiety (log-rank test, p < 0.001). Mean daily doses of escitalopram at the sixth month in the BoNT/A group was smaller than the placebo group (12.5 mg vs. 16.04 mg, p < 0.001). The number of patients who relapsed (HAMA total score ≥ 14 points) at 6 months of follow-up in the BoNT/A group was less than the placebo group (2.2% vs. 14.9%, p < 0.05). The rates of response (HAMA subtraction rate ≥ 50%) were 93.8% for the BoNT/A group and 75.5% for the placebo group (p < 0.05), and the rates of remission (HAMA < 7 points) were 87.5% for the BoNT/A group and 64.2% for the placebo group (p < 0.01) at the sixth month.

CONCLUSION

The combination of escitalopram with BoNT/A is a significantly effective intervention in improving clinical efficacy and reducing the recurrence in patients with GAD and comorbid headache, and we believe that this approach will be an additional treatment strategy for future treatment of comorbid headache in GAD. Therefore, we recommend that escitalopram combined with BoNT/A should be given as early as possible in GAD patients and comorbid headache.

How Does Botulinum Toxin Inhibit Itch?

Two decades after reports of the anti-pruritic effects of botulinum neurotoxins (BoNTs), there is still no approved product for the anti-itch indication of BoNTs, and most clinical case reports still focus on the off-label use of BoNTs for various itchy conditions. Few randomized clinical trials have been conducted with controversial results, and the beneficial effects of BoNTs against itch are mainly based on case studies and case series. These studies are valuable in presenting the potential application of BoNTs in chronic pruritic conditions, but due to the nature of these studies, they are categorized as providing lower levels of evidence or lower grades of recommendation. To obtain approval for the anti-pruritic indication of BoNTs, higher levels of evidence are required, which can be achieved through conducting large-scale and well-designed studies with proper control groups and established careful and reliable primary and secondary outcomes. In addition to clinical evidence, presenting the mechanism-based antipruritic action of BoNTs can potentially strengthen, accelerate, and facilitate the current efforts towards further investments in accelerating the field towards the potential approval of BoNTs for itchy conditions. This review, therefore, aimed to provide the state-of-the-art mechanisms underlying the anti-itch effect of BoNTs from basic studies that resemble various clinical conditions with itch as a hallmark. Evidence of the neuronal, glial, and immune modulatory actions of BoNTs in reducing the transmission of itch are presented, and future potential directions are outlined.

The contribution of autonomic mechanisms to pain in temporomandibular disorders: A narrative review

BACKGROUND

Temporomandibular disorders (TMD) are diagnosed based on symptom presentation and, like other functional pain disorders, often lack definitive pathology. There is a strong association between elevated stress levels and the severity of TMD-related pain, which suggests that alterations in autonomic tone may contribute to this pain condition.

OBJECTIVES

This narrative review examines the association between altered autonomic function and pain in TMD.

METHODS

Relevant articles were identified by searching PubMed and through the reference list of those studies.

RESULTS

TMD sufferers report an increased incidence of orthostatic hypotension. As in other chronic musculoskeletal pain conditions, TMD is associated with increased sympathetic tone, diminished baroreceptor reflex sensitivity and decreased parasympathetic tone. It remains to be determined whether ongoing pain drives these autonomic changes and/or is exacerbated by them. To examine whether increased sympathetic tone contributes to TMD-related pain through β₂ adrenergic receptor activation, clinical trials with the beta blocker propranolol have been undertaken. Although evidence from small studies suggested propranolol reduced TMD-related pain, a larger clinical trial did not find a significant effect of propranolol treatment. This is consistent with human experimental pain studies that were unable to demonstrate an effect of β₂ adrenergic receptor activation or inhibition on masticatory muscle pain. In preclinical models of temporomandibular joint arthritis, β₂ adrenergic receptor activation appears to contribute to inflammation and nociception, whereas in masticatory muscle, α₁ adrenergic receptor activation has been found to induce mechanical sensitization. Some agents used to treat TMD, such as botulinum neurotoxin A, antidepressants and α₂ adrenergic receptor agonists, may interact with the autonomic nervous system as part of their analgesic mechanism.

CONCLUSION

Even if dysautonomia turns out to be a consequence rather than a causative factor of painful TMD, the study of its role has opened up a greater understanding of the pathogenesis of this condition.

OnabotulinumtoxinA Dosing, Disease Severity, and Treatment Benefit in Patients With Cervical Dystonia: A Cohort Analysis From CD PROBE

Introduction

The Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy (CD PROBE) study (ClinicalTrials.gov identifier: NCT00836017), a multicenter, prospective, observational registry, was designed to identify real-world practices and outcomes for patients with cervical dystonia (CD) treated with onabotulinumtoxinA (onabotA). This secondary analysis from CD PROBE aims to determine the impact of presentation subtype on onabotA utilization and CD severity.

Materials and Methods

The study cohort includes those who completed all 3 treatments, 4 office visits, and had data recorded for all assessments. Patient outcomes were assessed with the Cervical Dystonia Impact Profile (CDIP-58), Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), and determination of CD severity. Treatment interval, dose, and adverse events (AEs) were also recorded. Data were stratified according to prior exposure to botulinum toxins (BoNTs) and analyzed with descriptive statistics.

Results

Torticollis was the most common presentation subtype in the study cohort (N = 350); the proportion of patients with torticollis was highest in those with severe disease. At each treatment, between 40.7 and 65.2% of those categorized as severe shifted to moderate or mild severity after treatment. Sustained improvements in CDIP-58 and TWSTRS were observed regardless of prior exposure to BoNTs. Dosing of onabotA generally increased from injection 1 to injection 3 and tended to be lower for patients naïve to BoNT. Median time interval between injections for the study cohort was 94.0 to 97.5 days. The most common AEs (dysphagia, muscular weakness) and injection intervals were similar between naïve vs. non-naïve patients; there were no serious treatment-related AEs.

Conclusions

This secondary cohort analysis from CD PROBE demonstrates that three repeat treatments with onabotA at intervals consistent with labeling attenuated disease severity and neck pain, resulting in sustained improvements in physician- and patient-reported outcomes. No new safety signals were identified.

Effects of onabotulinumtoxin A in patients concurrently diagnosed with chronic migraine encephalalgia and temporomandibular disorders: A retrospective case series

OBJECTIVE

Chronic migraine encephalalgia (CME) with concomitant temporomandibular disorder (TMD) is a serious illness with limited effective treatment options. This study explores the effectiveness of onabotulinumtoxinA (BtxA) as an adjunct therapeutic to TMJ arthroscopy in the relief of CME.

METHODS

A retrospective cohort study of patients receiving TMJ arthroscopy, with or without BtxA injections for CME, was conducted. Variables assessed include pain using a visual analog scale (VAS), maximal incisal opening (MIO), muscle soreness, and headache frequency and duration.

RESULTS

Sixty patients (44 BtxA, 16 Control), consisting of 56 (93.3%) females, met inclusion criteria. A significant reduction in pain is reported with patients receiving BtxA (p < 0.0001) on VAS as compared to Control group. BtxA treatment also significantly reduced headache frequency and duration (p < 0.05).

CONCLUSION

These results support the use of adjunctive BtxA treatment with arthroscopy for the treatment of CME in the context of TMD.

The pro-algesic effect of γ-aminobutyric acid (GABA) injection into the masseter muscle of healthy men and women

Background and aims

Preclinical studies have reported that activation of peripheral γ-aminobutyric acid A (GABAA) receptors may result in analgesia. The current study was conducted in young healthy men (n = 30) and women (n = 28) to determine whether injections of GABA into the masseter muscle reduce pain in a sex-related manner.

Methods

The effect of injection of GABA alone, or in combination with the non-inflammatory algogen glutamate, was assessed in two separate studies. Lorazepam, a positive allosteric modulator of the GABAA-receptor, was co-injected with GABA in both studies to explore the role of this receptor in muscle pain responses of healthy human volunteers. Masticatory muscle mechanical pain intensity was recorded on an electronic visual analogue scale (VAS) while muscle pain sensitivity was assessed by determining the pressure pain threshold (PPT), tolerance and maximal jaw opening (MJO) of the subjects prior to, and again after the various intramuscular injections.

Results

Intramuscular injection of GABA alone was reported to be significantly more painful, in a concentration related manner, than saline control injections, and this pain was further increased by co-injection of lorazepam with GABA. Co-injection of GABA with glutamate was found to significantly increase glutamate-evoked masseter muscle pain in men, but not in women. There was no effect of injections of either GABA alone, or GABA with glutamate, on PPT, tolerance or maximum jaw opening.

Conclusions

Injection of GABA into the human masseter muscle appears to excite nociceptors to produce muscle pain without a longer term effect on mechanical pain sensitivity in the muscle. The findings suggest that GABA-mediated pain in humans is produced through peripheral GABAA receptor activation. The mechanism underlying the sex-related difference in the effect of GABA on glutamate-evoked muscle pain was speculated to be due to a methodological artifact.

Implications

This study was designed to detect analgesic rather than algesic effects of peripherally administered GABA, and as a result, the concentration of glutamate chosen for injection was close to the maximal pain response for healthy women, based on previously determined pain-concentration response relationships for glutamate. This may explain the finding of greater pain in men than women, when GABA and glutamate were co-injected. Overall, the findings suggest that activation of peripheral GABAA receptors in human masticatory muscle produces pain, possibly due to depolarization of the masticatory muscle afferent fibers.

Antipruritic Effects of Botulinum Neurotoxins

This review explores current evidence to demonstrate that botulinum neurotoxins (BoNTs) exert antipruritic effects. Both experimental and clinical conditions in which botulinum neurotoxins have been applied for pruritus relief will be presented and significant findings will be highlighted. Potential mechanisms underlying antipruritic effects will also be discussed and ongoing challenges and unmet needs will be addressed.

OnabotulinumtoxinA Improves Pain in Patients With Post-Stroke Spasticity: Findings From a Randomized, Double-Blind, Placebo-Controlled Trial

CONTEXT

Patients with post-stroke spasticity (PSS) commonly experience pain in affected limbs, which may impact quality of life.

OBJECTIVES

To assess onabotulinumtoxinA for pain in patients with PSS from the BOTOX(®) Economic Spasticity Trial, a multicenter, randomized, double-blind, placebo-controlled trial.

METHODS

Patients with PSS (N = 273) were randomized to 22- to 34-week double-blind treatment with onabotulinumtoxinA + standard care (SC) or placebo injection + SC and were eligible to receive open-label onabotulinumtoxinA up to 52 weeks. Assessments included change from baseline on the 11-point pain numeric rating scale, proportion of patients with baseline pain ≥4 achieving ≥30% and ≥50% improvement in pain, and pain interference with work at Week 12, end of double-blind treatment, and Week 52.

RESULTS

At baseline, most patients (74.3%) experienced pain and 47.4% had pain ≥4 (pain subgroup). Mean pain reduction from baseline at Week 12 was significantly greater with onabotulinumtoxinA + SC (-0.77, 95% CI -1.14 to -0.40) than placebo + SC (-0.13, 95% CI -0.51 to 0.24; P < 0.05). Higher proportions of patients in the pain subgroup achieved ≥30% and ≥50% reductions in pain at Week 12 with onabotulinumtoxinA + SC (53.7% and 37.0%, respectively) compared with placebo (28.8% and 18.6%, respectively; P < 0.05). Reductions in pain were sustained through Week 52. Compared with placebo + SC, onabotulinumtoxinA consistently reduced pain interference with work.

CONCLUSION

This is the first randomized, placebo-controlled trial demonstrating statistically significant and clinically meaningful reductions in pain and pain interference with work with onabotulinumtoxinA in patients with PSS.

Effects of OnabotulintoxinA on Habituation of Laser Evoked Responses in Chronic Migraine

Onabotulintoxin A (BontA) is an efficacious preventive treatment for chronic migraine, though the specific mechanism of action is still under discussion. The study aims: (1) To evaluate pain processing modifications in chronic migraine patients (CM) under single BontA administration in pericranial muscles, by means of CO² Laser Evoked Potentials (LEPs) obtained by the stimulation of the skin over the right frontal and trapezius injection sites and hand dorsum, in a double blind placebo controlled crossover design. (2) To correlate main LEPs findings with clinical outcome after one year of BontA treatment. Twenty refractory CM patients were included in the analysis. The LEPs were recorded in basal conditions and seven days after BontA (PREEMPT protocol) and saline solution injection. The N1, N2 and P2 amplitude and latencies and N2P2 habituation index were evaluated and correlated with the percent change of headache frequency after one year of toxin treatment. After seven days of BontA treatment, a normalization of the trigeminal habituation index was observed, which was correlated with the clinical outcome after one year of BontA therapy. Patients displaying trigeminal LEPs facilitation at T0 time showed a more efficient therapeutic outcome. Neurotoxin may exert a modulating effect on trigeminal nociception, normalizing central neurotransmission.

How botulinum toxin in neurogenic detrusor overactivity can reduce upper urinary tract damage?

Intradetrusor injections of botulinum toxin are the cornerstone of medical treatment of neurogenic detrusor overactivity. The primary aim of this treatment is to ensure a low pressure regimen in the urinary bladder, but the mechanisms leading to long-term protection of the urinary tract remain poorly understood. In this paper, we highlight the potential benefits of intradetrusor injections of botulinum toxin regarding local effects on the bladder structures, urinary tract infections, stone disease, vesico ureteral reflux, hydronephrosis, renal function based on a comprehensive literature review.

Neck Pain and Cervical Dystonia: Treatment Outcomes from CD PROBE (Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy)

BACKGROUND

Pain is a prevailing feature of cervical dystonia (CD), the most common form of focal dystonia. This analysis examined pain relief after onabotulinumtoxinA treatment in CD subjects with moderate/severe pain from the Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy (CD PROBE).

METHODS

CD PROBE was a prospective, multicenter, observational registry of CD subjects who were naïve to botulinum toxin (BoNT), new to physician, or had not received BoNT within ≥ 16 weeks if in a clinical trial. Subjects were eligible for 3 treatments, with variable session intervals. Descriptive and inferential statistics were utilized to evaluate the change in pain scores in the population with moderate/severe neck pain at baseline (Pain Numeric Rating Scale [PNRS] score 4 to 10).

RESULTS

Of 1046 enrolled, 733 (70.7%) had moderate/severe neck pain at baseline. Postinjection pain questionnaire responses 4 to 6 weeks after each of the 3 treatments revealed that a majority of subjects (67.1%, 72.4%, and 76.4%) reported pain relief; mean time to pain relief was 7.1, 7.4, and 7.6 days. All pain scales showed significant improvements from baseline to final visit (all P < 0.0001): PNRS, mean 6.6 to 3.8; CD Impact Profile-58 Pain and Discomfort subscale, mean 78.7 to 56.5; and Toronto Western Spasmodic Torticollis Rating Scale Pain subscale, mean 12.6 to 8.5. Multivariable regression models showed that initial pain score significantly contributed to the final pain score for all scales.

CONCLUSION

Results from this real-world clinical registry indicate that a majority of CD subjects with moderate/severe neck pain experience significant relief following onabotulinumtoxinA treatment.

Current status and future directions of botulinum neurotoxins for targeting pain processing

Current evidence suggests that botulinum neurotoxins (BoNTs) A1 and B1, given locally into peripheral tissues such as skin, muscles, and joints, alter nociceptive processing otherwise initiated by inflammation or nerve injury in animal models and humans. Recent data indicate that such locally delivered BoNTs exert not only local action on sensory afferent terminals but undergo transport to central afferent cell bodies (dorsal root ganglia) and spinal dorsal horn terminals, where they cleave SNAREs and block transmitter release. Increasing evidence supports the possibility of a trans-synaptic movement to alter postsynaptic function in neuronal and possibly non-neuronal (glial) cells. The vast majority of these studies have been conducted on BoNT/A1 and BoNT/B1, the only two pharmaceutically developed variants. However, now over 40 different subtypes of botulinum neurotoxins (BoNTs) have been identified. By combining our existing and rapidly growing understanding of BoNT/A1 and /B1 in altering nociceptive processing with explorations of the specific characteristics of the various toxins from this family, we may be able to discover or design novel, effective, and long-lasting pain therapeutics. This review will focus on our current understanding of the molecular mechanisms whereby BoNTs alter pain processing, and future directions in the development of these agents as pain therapeutics.

Botulinum Toxin Type a as a Therapeutic Agent against Headache and Related Disorders

Botulinum neurotoxin A (BoNT/A) is a toxin produced by the naturally-occurring Clostridium botulinum that causes botulism. The potential of BoNT/A as a useful medical intervention was discovered by scientists developing a vaccine to protect against botulism. They found that, when injected into a muscle, BoNT/A causes a flaccid paralysis. Following this discovery, BoNT/A has been used for many years in the treatment of conditions of pathological muscle hyperactivity, like dystonias and spasticities. In parallel, the toxin has become a “glamour” drug due to its power to ward off facial wrinkles, particularly frontal, due to the activity of the mimic muscles. After the discovery that the drug also appeared to have a preventive effect on headache, scientists spent many efforts to study the potentially-therapeutic action of BoNT/A against pain. BoNT/A is effective at reducing pain in a number of disease states, including cervical dystonia, neuropathic pain, lower back pain, spasticity, myofascial pain and bladder pain. In 2010, regulatory approval for the treatment of chronic migraine with BoNT/A was given, notwithstanding the fact that the mechanism of action is still not completely elucidated. In the present review, we summarize experimental evidence that may help to clarify the mechanisms of action of BoNT/A in relation to the alleviation of headache pain, with particular emphasis on preclinical studies, both in animals and humans. Moreover, we summarize the latest clinical trials that show evidence on headache conditions that may obtain benefits from therapy with BoNT/A.

Blockade of glutamate release by botulinum neurotoxin type A in humans: a dermal microdialysis study

BACKGROUND

The analgesic action of botulinum neurotoxin type A (BoNTA) has been linked to the blockade of peripheral release of neuropeptides and neurotransmitters in animal models; however, there is no direct evidence of this in humans.

OBJECTIVES

To investigate the effect of BoNTA on glutamate release in humans, using an experimental model of pain and sensitization provoked by capsaicin plus mild heat.

METHODS

Twelve healthy volunteers (six men, six women) were pretreated with BoNTA (10 U) on the volar forearm and with a saline control on the contralateral side. Dermal microdialysis was applied one week later to collect interstitial samples before and after the application of a capsaicin patch (8%) plus mild heat (40°C⁄60 min) to provoke glutamate release, pain and vasodilation. Samples were collected every hour for 3 h using linear microdialysis probes (10 mm, 100 kD). Dialysate was analyzed for glutamate concentration. Pain intensity and skin vasomotor reactions (temperature and blood flow changes) were also recorded.

RESULTS

BoNTA significantly reduced glutamate release compared with saline (P<0.05). The provoked pain intensity was lower in the BoNTA-pretreated arm (P<0.01). The reduction in pain scores was not correlated with glutamate level. Cutaneous blood flow (P<0.05), but not cutaneous temperature (P≥0.05), was significantly reduced by BoNTA. There was a correlation between glutamate level and skin blood flow (r=0.58⁄P<0.05) but not skin temperature (P≥0.05). No differences according to sex were observed in any response.

CONCLUSIONS

The present study provided the first direct evidence supporting the inhibitory effect of BoNTA on glutamate release in human skin, which is potentially responsible for some of the analgesic action of BoNTA.