Extracranial injections of botulinum neurotoxin type A inhibit intracranial meningeal nociceptors' responses to stimulation of TRPV1 and TRPA1 channels: Are we getting closer to solving this puzzle?

Wear-Off of OnabotulinumtoxinA Effect Over the Treatment Interval in Chronic Migraine: A Retrospective Chart Review With Analysis of Headache Diaries

OBJECTIVE

To quantify wear-off of the response to OnabotulinumtoxinA (OnabotA) treatment over the treatment cycle in chronic migraine at group and individual level.

BACKGROUND

OnabotA administered quarterly is an effective treatment for chronic migraine. However, some patients report that headache recurs before the scheduled follow-up injection.

METHODS

In this retrospective chart review performed in 6 university outpatient centers or private practices specialized in headache treatment, 112 patients with a ≥30% response to OnabotA who completed headache diaries over 13 weeks after OnabotA treatment were included (age [mean ± SD] 45 ± 12 years, 82% female, headache days/month at baseline 24 ± 6).

RESULTS

Compared to weeks 5 to 8 after injection, headache days/week increased significantly in weeks 12 (+0.52 ± 1.96, 95% CI [0.15, 0.88], P < .009) and 13 (+1.15 ± 1.95, CI[0.79, 1.52], P < .001), demonstrating significant wear-off of the OnabotA effect. Similarly, acute medication days/week significantly increased in weeks 12 (0.38±1.67, CI [0.06, 0.69], P ≤ .027) and 13 (+0.83 ± 1.76, CI [0.49, 1.16], P < .001). At an individual level, 57 patients (51%) showed ≥30% wear-off by weeks 12 and 13, and 28 patients (25%) showed ≥30% wear-off already by weeks 10 and 11. Age, gender, OnabotA dose or cycle number, or headache center did not predict individual wear-off.

CONCLUSIONS

These data show that in clinical practice, on average the response of chronic migraine patients to OnabotA injection shows a clinically significant wear-off from week 12 after treatment. About 25% of the patients experience wear-off even by weeks 10 and 11. It must be noted that wear-off detected in a real-world study on OnabotA responders can be due to wear-off of a pharmacological OnabotA effect or a placebo effect, or to regression to the mean effects. This wear-off phenomenon may negatively affect quality of life of chronic migraine patients under OnabotA treatment. The best way to counteract wear-off remains to be determined.

Modifications to the PREEMPT Protocol for OnabotulinumtoxinA Injections for Chronic Migraine in Clinical Practice

OBJECTIVE

To assess the PREEMPT protocol modifications that have developed in clinical practice over time.

BACKGROUND

The United States Food and Drug Administration approved the 155-unit fixed-dose, fixed-site PREEMPT protocol of onabotulinumtoxinA (BoNT-A) injections for migraine prevention 9 years ago.

METHODS

This is an anonymous survey with free text response options of Headache Medicine clinicians.

RESULTS

Out of the 878 contacted Headache Medicine clinicians, 182 (20.7%) completed the survey. Of the 182 respondents, 141 (77.5%) reported that they did not always follow the PREEMPT protocol. Of the 182 respondents, 128 (70%) changed the number of injections, 115 (63%) changed the total units of BoNT-A injected, 105 (57.7%) altered the location of injection sites (58%); 101 (55.5%) do not aspirate to ensure the absence of blood return; 22 (12.1%) changed the dilution; and 4 (2.2%) added lidocaine. The main reported reasons for changes in number, dose, and location of injections included adapting to the patients' pain, anatomy, and preferences.

CONCLUSIONS

The wide inter- and intra-personal variations in BoNT-A injections for chronic migraine prevention seen in this survey raise concerns about the standardization of the procedure and suggest that an advisory protocol containing more evidence and discussion of the reasoning behind the recommendations might be more helpful than the current prescriptive protocol.

Mechanism of Action of OnabotulinumtoxinA in Chronic Migraine: A Narrative Review

Objective

To review the literature on the mechanism of action of onabotulinumtoxinA in chronic migraine.

Background

OnabotulinumtoxinA is a chronic migraine preventive treatment that significantly reduces headache frequency. The traditional mechanism described for onabotulinumtoxinA – reducing muscle contractions – is insufficient to explain its efficacy in migraine, which is primarily a sensory neurological disease.

Methods

A narrative literature review on the mechanism of action of onabotulinumtoxinA in chronic migraine.

Results

Following injection into tissues, onabotulinumtoxinA inhibits soluble N‐ethylmaleimide‐sensitive fusion attachment protein receptor (SNARE)‐mediated vesicle trafficking by cleaving one of its essential proteins, soluble N‐ethylmaleimide‐sensitive fusion attachment protein (SNAP‐25), which occurs in both motor and sensory nerves. OnabotulinumtoxinA inhibits regulated exocytosis of motor and sensory neurochemicals and proteins, as well as membrane insertion of peripheral receptors that convey pain from the periphery to the brain, because both processes are SNARE dependent. OnabotulinumtoxinA can decrease exocytosis of pro‐inflammatory and excitatory neurotransmitters and neuropeptides such as substance P, calcitonin gene‐related peptide, and glutamate from primary afferent fibers that transmit nociceptive pain and participate in the development of peripheral and central sensitization. OnabotulinumtoxinA also decreases the insertion of pain‐sensitive ion channels such as transient receptor potential cation channel subfamily V member 1 (TRPV1) into the membranes of nociceptive neurons; this is likely enhanced in the sensitized neuron. For chronic migraine prevention, onabotulinumtoxinA is injected into 31‐39 sites in 7 muscles of the head and neck. Sensory nerve endings of neurons whose cell bodies are located in trigeminal and cervical ganglia are distributed throughout the injected muscles, and are overactive in people with migraine. Through inhibition of these sensory nerve endings, onabotulinumtoxinA reduces the number of pain signals that reach the brain and consequently prevents activation and sensitization of central neurons postulated to be involved in migraine chronification.

Conclusion

OnabotulinumtoxinA likely acts via sensory mechanisms to treat chronic migraine.

Therapeutic potential of pharmacological agents targeting TRP channels in CNS disorders

Central nervous system (CNS) disorders like Alzheimer's disease (AD), Parkinson disease (PD), stroke, epilepsy, depression, and bipolar disorder have a high impact on both medical and social problems due to the surge in their prevalence. All of these neuronal disorders share some common etiologies including disruption of Ca²⁺ homeostasis and accumulation of misfolded proteins. These misfolded proteins further disrupt the intracellular Ca²⁺ homeostasis by disrupting the activity of several ion channels including transient receptor potential (TRP) channels. TRP channel families include non-selective Ca²⁺ permeable channels, which act as cellular sensors activated by various physio-chemical stimuli, exogenous, and endogenous ligands responsible for maintaining the intracellular Ca²⁺ homeostasis. TRP channels are abundantly expressed in the neuronal cells and disturbance in their activity leads to various neuronal diseases. Under the pathological conditions when the activity of TRP channels is perturbed, there is a disruption of the neuronal homeostasis through increased inflammatory response, generation of reactive oxygen species, and mitochondrial dysfunction. Therefore, there is a potential of pharmacological interventions targeting TRP channels in CNS disorders. This review focuses on the role of TRP channels in neurological diseases; also, we have highlighted the current insights into the pharmacological modulators targeting TRP channels.

[Osteopathy under scrutiny]

Osteopathic medicine is a medical specialty that enjoys a high level of recognition and increasing popularity among patients. High-quality education and training are essential to ensure good and safe patient treatment. At a superficial glance, osteopathy could be misunderstood as a myth; accurately considered, osteopathic medicine is grounded in medical and scientific knowledge and solid theoretical and practical training. Scientific advances increasingly confirm the empirical experience of osteopathy. Although more studies on its efficacy could be conducted, there is sufficient evidence for a reasonable application of osteopathy. Current scientific studies show how a manually executed osteopathic intervention can induce tissue and even cellular reactions. Because the body actively responds to environmental stimuli, osteopathic treatment is considered an active therapy. Osteopathic treatment is individually applied and patients are seen as an integrated entity. Because of its typical systemic view and scientific interpretation, osteopathic medicine is excellently suited for interdisciplinary cooperation. Further work on external evidence of osteopathy is being conducted, but there is enough knowledge from the other pillars of evidence-based medicine (EBM) to support the application of osteopathic treatment. Implementing careful, manual osteopathic examination and treatment has the potential to cut healthcare costs. To ensure quality, osteopathic societies should be intimately involved and integrated in the regulation of the education, training, and practice of osteopathic medicine.

Dual Therapy With Anti-CGRP Monoclonal Antibodies and Botulinum Toxin for Migraine Prevention: Is There a Rationale?

OBJECTIVE

To narratively review the pathophysiological rationale of dual therapy with anti-calcitonin gene-related peptide monoclonal antibodies and botulinum toxin type A in treatment-resistant chronic migraine prevention.

BACKGROUND

For the prevention of chronic migraine, several pharmacological therapies are available, including oral medications, botulinum toxin type A, and the newly approved monoclonal antibodies targeting calcitonin gene-related peptide or its receptor. However, monotherapy does not yield benefits in some affected individuals, which raises the question of whether dual therapy with monoclonal antibodies and botulinum toxin type A hold promise in patients with treatment-resistant chronic migraine.

METHOD

We searched MEDLINE for articles published from database inception to December 31st, 2019. Publications were largely selected from the past 10 years but commonly referenced and highly regarded older publications were not excluded.

RESULTS

Preclinical data suggest that anti-calcitonin gene-related peptide monoclonal antibodies and botulinum toxin type A have synergistic effects within the trigeminovascular system. Of note, findings indicate that fremanezumab - an antibody targeting the calcitonin gene-related peptide - mainly prevents the activation of Aδ-fibers, whereas botulinum toxin type A prevents the activation of C-fibers.

CONCLUSION

There is currently only indirect preclinical evidence to support a rationale for dual therapy with anti-calcitonin gene-related peptide monoclonal antibodies and botulinum toxin type A for chronic migraine prevention. Rigorous studies evaluating clinical efficacy, safety, and cost-effectiveness are needed.

Novelty in Inflammation and Immunomodulation in Migraine

BACKGROUND

Migraine is a diffuse and disabling disease. Its pathophysiology is complex and involves both central and peripheral dysfunctions.

OBJECTIVE

This review will discuss the pathogenesis of migraine from the origin of the neuro-inflammatory theory, to the modern pathophysiological model and the latest therapies.

METHODS

PUBMED and EMBASE (up to May 2019) were searched for: migraine, inflammation, immunomodulation. An additional search was carried out from the bibliography of previous review articles.

RESULTS

Migraine was thought to be mainly a vascular disorder, according to the so-called "vascular theory". Based on animal models, a new hypothesis called "the neuro-inflammatory" was conceived at the end of the 20th century. The growing knowledge about the trigeminovascular system and its role in the inflammatory-pain pathway, allowed to identify other specific neurotransmitters, such as the Calcitonin Gene-Related Peptide and Pituitary Adenylate Cyclase-Activating Peptide. Evidence was provided that the inflammatory-pain system could become sensitised and, due to this sensitisation, the pain could also perpetuate, even in the absence of any triggers of the migraine attack. At last, brain immune cells modification during cortical spreading depression in migraine was demonstrated, along with the existence and function of the glymphatic system. The better comprehension of the immune system abnormalities allowed the development of new immunomodulating drugs: the monoclonal antibodies against the CGRP or the CGRP receptor. Moreover, new insights into the molecular mechanism of CGRP, and the function of C-fibres and Aδ-fibres, highlighted the mechanism of action of Botulinum Toxin type A in the treatment of chronic migraine.

The Use of Botulinum Toxin in the Management of Headache Disorders

Tremendous progress has been made in the past decades for the treatment of headache disorders. Chronic migraine is the most disabling type of headache and requires the use of acute and preventive medications, many of which are associated with adverse events that limit patient adherence. Botulinum toxin (BoNT) serotype A, a neurotoxin derived from certain strains of Clostridium, disrupts neuropeptide secretion and receptor translocation related to trigeminal nociception, thereby preventing pain sensitization through peripheral and possibly central mechanisms. Ever since the first randomized controlled trial on onabotulinumtoxinA (onabotA) for migraine was published two decades ago, onabotA has been the only BoNT formulation approved for use in the prevention of chronic migraine. Superior tolerability and efficacy have been demonstrated on multiple migraine endpoints in many controlled trials and real-life studies. OnabotA is a safe and efficacious treatment for chronic migraine and possibly high-frequency episodic migraine. Further research is still needed to understand its mechanism of action to fully develop its therapeutic potential.

Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease

The transient receptor potential ankyrin (TRPA) channels are Ca²⁺-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH₂ terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca²⁺, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.

Botulinum toxin injections to cranial sutures for chronic migraine Rewinding the technique using ultrasound imaging

The treatment of chronic migraine headache is quite challenging and new alternatives are still being explored for its management. Onabotulinum toxin A (BoNT-A) applied into extracranial muscles has been shown to inhibit the release of acetylcholine and local nociceptive peptides at the sensory nerve endings. As the highest concentration of extracranial pain fibers are located at/nearby the sutures, extracranial applications of BoTN-A are suggested to be performed to sutures rather than into the head and neck muscles in the treatment of chronic migraine. Moreover, in an animal study, BoTN-A is found to be more effective for decreasing the chemosensitivity of meningeal nociceptors when the total dose is injected along the sutures in comparison to being divided into sutures and cranial muscles. Of note, since BoNT-A injections performed with the blind/nontargeted technique have lower effectivity and several complications (muscle weakness, ptosis, facial paresis, etc.), the use of ultrasound guidance for targeting the cranial sutures is definitely expected to provide technical ease, better pain relief and toxin tolerance in chronic migraine.

Plasma Levels of Oxidative Stress Markers, before and after BoNT/A Treatment, in Chronic Migraine

The pathophysiological mechanisms of migraine transformation are debated. Modifications of plasma oxidative stress biomarkers have been described in chronic migraine. OnabotulintoxinA (BoNT/A) treatment, approved for chronic migraine prophylaxis, possibly reduces pain neurotransmitters release and oxidative stress products. Aims of our study were to investigate differences in the levels of selected plasmatic oxidative stress biomarkers (Advanced Oxidation Protein Products (AOPP), Ferric Reducing Antioxidant Power (FRAP), Thiolic Groups (SH)) comparing chronic migraineurs (CM) and healthy controls (HC). We also explored possible clinical and biochemical modifications in the CM group after six months of treatment with BoNT/A. At the baseline, we found higher values of AOPP (p < 0.001), and lower values of SH (p < 0.001) and FRAP (p = 0.005) in the CM group. At the six-month follow-up we found a reduction of AOPP (p < 0.001) and an increase of FRAP (p < 0.001) and SH (p = 0.023) within the CM group. BoNT/A treatment improved migraine symptoms in the CM group. We confirmed previous reports of imbalanced antioxidant mechanisms in chronic migraine showing lower antioxidant capacities in patients than controls. BoNT/A improved the levels of plasma oxidative stress biomarkers and confirmed its role as an effective prophylactic treatment for CM. Other studies should investigate the potential antioxidant properties of BoNT/A treatment.

Peri-Incisional Botulinum Toxin Therapy for Treatment of Intractable Head Pain After Lateral Skull Base Surgery: A Case Series

OBJECTIVE

The objective of this case series was to describe botulinum toxin therapy as a novel treatment of intractable head pain following lateral skull base surgery.

BACKGROUND

Intractable headaches following lateral skull base surgery are described in 23%-75% of patients and can significantly impact quality of life. Currently, the etiology of the headaches is unclear and treatment options are limited. Botulinum toxin is indicated for a multitude of functional and cosmetic reasons, including chronic migraine, and has been further described in treatment of various postsurgical pain syndromes.

METHODS

In this case series, 4 patients underwent subcutaneous peri-incisional injections of botulinum toxin for intractable headache and head pain syndromes. Three patients had undergone lateral skull base surgery and the fourth patient had undergone a temporoparietal fascial flap harvest. Average injection dose ranged from 20 to 60 units with an average duration of effect ranging from 2 weeks to 4 months.

RESULTS

All patients experienced significant relief of chronic head pain and returned for additional peri-incisional botulinum toxin injections, suggesting meaningful patient-perceived value.

CONCLUSIONS

Botulinum toxin therapy may represent a novel treatment for intractable head pain following lateral skull base surgery and temporoparietal fascial flap harvest. This study represents a small case series and, although 100% of the patients who were treated significantly improved, future inquiry is necessary to confirm these findings.

Exploring the effects of extracranial injections of botulinum toxin type A on prolonged intracranial meningeal nociceptors responses to cortical spreading depression in female rats

Background

Botulinum neurotoxin type A, an FDA-approved prophylactic drug for chronic migraine, is thought to achieve its therapeutic effect through blocking activation of unmyelinated meningeal nociceptors and their downstream communications with myelinated nociceptors and potentially the vasculature and immune cells. Prior investigations to determine botulinum neurotoxin type A effects on meningeal nociceptors were carried out in male rats and tested with stimuli that act outside the blood brain barrier. Here, we sought to explore the effects of extracranial injections of botulinum neurotoxin type A on activation of meningeal nociceptors by cortical spreading depression, an event which occurs inside the blood brain barrier, in female rats.

Material and methods

Using single-unit recording, we studied myelinated C- and unmyelinated Aδ-meningeal nociceptors' responses to cortical spreading depression 7–14 days after injection of botulinum neurotoxin type A or saline along calvarial sutures.

Results

In female rats, responses to cortical spreading depression were typically more prolonged and, in some cases, began at relatively longer latencies post-cortical spreading depression, than had been observed in previous studies in male rats. Extracranial administration of botulinum neurotoxin type A reduced significantly the prolonged firing of the meningeal nociceptors, in the combined sample of Aδ- and C-fiber, but not their response probability.

Discussion

The findings suggest that the mechanism of action by which botulinum neurotoxin type A prevents migraine differ from the one by which calcitonin gene-related peptide monoclonal antibodies prevent migraine and that even when the origin of migraine is central (i.e. in the cortex), a peripherally acting drug can intercept/prevent the headache.

Botulinum toxin type A reduces the expression of transient receptor potential melastatin 3 and transient receptor potential vanilloid type 4 in the trigeminal subnucleus caudalis of a rat model of trigeminal neuralgia

This study was designed to investigate the expression of transient receptor potential melastatin 3 (TRPM3) and transient receptor potential vanilloid type 4 (TRPV4) in the trigeminal spinal subnucleus caudalis of a rat model of trigeminal neuralgia (TN). The influence of botulinum toxin type A (BTX-A) on the expression of these channels was also explored. In this study, a model was established involving chronic constriction injury to the infraorbital nerve (ION-CCI), inducing TN. To explore the effects of BTX-A and whether it was dose related, rats were divided randomly into four groups: a control group, an ION-CCI group, a 3 U group, and a 10 U group (which received 3 and 10 U/kg BTX-A injections, respectively). Von Frey hairs were used to determine the pain threshold of the rats. The expression of TRPM3 and TRPV4 in the trigeminal spinal subnucleus caudalis was detected using western blots and immunohistochemistry. The pain thresholds of rats decreased to a minimum 14 days after ION-CCI. Compared with the ION-CCI group, the pain thresholds of the 3 and 10 U groups were significantly higher 4 days after the subcutaneous injection of BTX-A (P<0.05). The expression of TRPM3 and TRPV4 in the ION-CCI group was significantly higher than that in the control group (P<0.05). TRPM3 and TRPV4 expression in the 3 and 10 U groups was significantly lower than that in the ION-CCI group (P<0.05). In conclusion, overexpression of TRPM3 and TRPV4 can jointly mediate the occurrence of mechanical hyperalgesia in TN. The analgesic effects of BTX-A may be related to the inhibition of TRPM3 and TRPV4 expression.

Pathophysiological Mechanisms in Migraine and the Identification of New Therapeutic Targets

Migraine is a strongly disabling disease characterized by a unilateral throbbing headache lasting for up to 72 h for each individual attack. There have been many theories on the pathophysiology of migraine throughout the years. Currently, the neurovascular theory dominates, suggesting clear involvement of the trigeminovascular system. The most recent data show that a migraine attack most likely originates in the hypothalamus and activates the trigeminal nucleus caudalis (TNC). Although the mechanisms are unknown, activation of the TNC leads to peripheral release of calcitonin gene-related protein (CGRP), most likely from C-fibers. During the past year monoclonal antibodies against CGRP or the CGRP receptor have emerged as the most promising targets for migraine therapy, and at the same time established the strong involvement of CGRP in the pathophysiology of migraine. The viewpoint presented here focuses further on the activation of the CGRP receptor on the sensory Aδ-fiber, leading to the sensation of pain. The CGRP receptor activates adenylate cyclase, which leads to an increase in cyclic adenosine monophosphate (cAMP). We hypothesize that cAMP activates the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, triggering an action potential sensed as pain. The mechanisms behind migraine pain on a molecular level, particularly their importance to cAMP, provide clues to potential new anti-migraine targets. In this article we focus on the development of targets related to the CGRP system, and further include novel targets such as the pituitary adenylate cyclase-activating peptide (PACAP) system, the serotonin 5-HT_1F receptor, purinergic receptors, HCN channels, adenosine triphosphate-sensitive potassium channels (K_ATP), and the glutaminergic system.

CALCA and TRPV1 genes polymorphisms are related to a good outcome in female chronic migraine patients treated with OnabotulinumtoxinA

Background

Some variables have been proposed as predictors of efficacy of OnabotulinumtoxinA in chronic migraine patients, but data available are inconclusive. We aimed to analyse the influence of single nucleotide polymorphisms in the response to OnabotulinumtoxinA.

Methods

We included 156 female patients treated with OnabotulinumtoxinA accordingly to PREEMPT paradigm in three headache units. OnabotulinumtoxinA was offered to patients that had not responded to topiramate and at least one other preventative. Age at first procedure was 43.7 ± 11.8 years (16–74). Patients with a reduction of at least 50% in the number of migraine days after two OnabotulinumtoxinA procedures were considered as responders. We analysed 25 polymorphisms selected for their relevance regarding migraine pathophysiology and their association with migraine according to previously published genome-wide association studies. Genotyping was performed using KASP probes and a LightCycler-480 (Roche-Diagnostics). Allelic, genotypic frequencies and dominance/recesivity hypothesis of the allelic variants were compared between responders and non-responders by Fisher’s exact test.

Results

Response to treatment with OnabotulinumtoxinA was achieved in 120 patients (76,9%). Two polymorphisms showed differences: CALCA rs3781719, where allele C represents 26.9% in responders and 40.9% in non-responders (p = 0.007, OR = 3.11 (1.33–7.26)); and TRPV1 rs222749, where allele A represents 4.17% in responders and 12.5% in non-responders (p = 0.013, OR = 3.29 (1.28–8.43)). No significant differences in rest of polymorphisms or clinical or demographic variables were found.

Conclusions

Polymorphic variations of CALCA and TRPV1 genes might play a role as prognostic markers of efficacy of OnabotulinumtoxinA in chronic migraine female patients in our population.

TRP Channels and Migraine: Recent Developments and New Therapeutic Opportunities

Migraine is the second-most disabling disease worldwide, and the second most common neurological disorder. Attacks can last many hours or days, and consist of multiple symptoms including headache, nausea, vomiting, hypersensitivity to stimuli such as light and sound, and in some cases, an aura is present. Mechanisms contributing to migraine are still poorly understood. However, transient receptor potential (TRP) channels have been repeatedly linked to the disorder, including TRPV1, TRPV4, TRPM8, and TRPA1, based on their activation by pathological stimuli related to attacks, or their modulation by drugs/natural products known to be efficacious for migraine. This review will provide a brief overview of migraine, including current therapeutics and the link to calcitonin gene-related peptide (CGRP), a neuropeptide strongly implicated in migraine pathophysiology. Discussion will then focus on recent developments in preclinical and clinical studies that implicate TRP channels in migraine pathophysiology or in the efficacy of therapeutics. Given the use of onabotulinum toxin A (BoNTA) to treat chronic migraine, and its poorly understood mechanism, this review will also cover possible contributions of TRP channels to BoNTA efficacy. Discussion will conclude with remaining questions that require future work to more fully evaluate TRP channels as novel therapeutic targets for migraine.

Pharmacological differences and clinical implications of various botulinum toxin preparations: a critical appraisal

Three different type A botulinum neurotoxins (BoNTAs) - onabotulinumtoxinA, abobotulinumtoxinA and incobotulinumtoxinA) - are currently marketed in Europe to treat several conditions. Differences between BoNTA preparations, which depend on their specific biotypes and manufacturing processes, lead to clinically relevant pharmacotherapeutic dissimilarities. All three available products are separately recognized and reviewed in American Academy of Neurology guidelines. The neurotoxin load/100U is likewise different among the different BoNTAs, with the result that the specific potency of the 150kD BoNTA neurotoxin is calculated as 137 units/ng for onabotulinumtoxinA, 154 units/ng for abobotulinumtoxinA, and 227 units/ng for incobotulinumtoxinA. It is important for clinicians to have all three BoNTAs available in order to choose the most suitable preparation for the specific indication in the single patient. Commercially available BoNTAs must be recognized as different from one another, and therefore as non-interchangeable. The essential experience of the clinician is of the utmost importance in choosing the most appropriate treatment.

Emerging drugs for migraine treatment: an update

Introduction: Migraine is a very frequent and disabling neurological disorder. The current treatment options are old, generally poorly tolerated and not migraine-specific, reflecting the low priority of migraine research and highlighting the vast unmet need in its management. Areas covered: Advancement in the understanding of migraine pathophysiological mechanisms and identification of novel potentially meaningful targets have resulted in a multitude of emerging acute and preventive treatments. Here we review the known putative migraine pathophysiological mechanisms in order to understand the rationale of the most promising novel treatments targeting the Calcitonin-Gene-Related Peptide receptor and ligand and the 5 hydroxytryptamine (5-HT)1F receptor. Key findings on the phase II and phase III clinical trials on these treatments will be summarized. Furthermore, a critical analysis on failed trials of potentially meaningful targets such the nitric oxide and the orexinergic pathways will be conducted. Future perspective will be outlined. Expert opinion: The recent approval of Erenumab and Fremanezumab is a major milestone in the therapy of migraine since the approval of triptans. Several more studies are needed to fully understand the clinical potential, long-term safety and cost-effectiveness of these therapies. This paramount achievement should stimulate the development of further research in the migraine field.

Anatomical Look Into OnabotulinumtoxinA Injection for Chronic Migraine Headache

BACKGROUND AND OBJECTIVES

While existing studies about onabotulinumtoxinA for chronic migraines have focused on injection location and appropriate dosing, little consideration has been given to patient body habitus and its potential impact on efficacy. We hypothesized that with increasing patient body mass index (BMI) there would be more subcutaneous fat separating targeted muscle groups from the skin surface, such that standard 0.5-inch needles used in existing protocols may not allow intramuscular injection. This may have implications for treatment planning.

METHODS

Anatomically normal computed tomography scans of the head, neck, and face were randomly selected. Subjects were stratified into 4 groups based on BMI, with 30 patients in each group. Four standardized locations were chosen to obtain measurements from the skin surface to the underlying muscle fascia, including (1) frontalis, (2) temporalis, (3) semispinalis capitis, and (4) trapezius.

RESULTS

Median depth for the temporalis was 12.65 mm (Q1 = 9.32 mm, Q3 = 15.08 mm) for the BMI greater than 35 kg/m group. Median depth for the semispinalis capitis was 13.77 mm (Q1 = 10.3 mm, Q3 = 15.7 mm) for the BMI 30 to 35 kg/m group, and 14.75 mm (Q1 = 11.00, Q3 = 17.00 mm) for the BMI greater than 35 kg/m group. Median depth for the trapezius was 13.95 mm (Q1 = 10.18 mm, Q3 = 19.00 mm) for the BMI greater than 35 kg/m group. These medians exceeded the length of the standard 0.5-inch (12.-mm) needle used in existing protocols.

CONCLUSIONS

Our study demonstrates that with increasing BMI there is a greater distance between the skin surface and the muscle fascia of muscles that are targeted for injection in standard chronic migraine botulinum toxin injection protocols. Because of this, patient body habitus may be an important factor in injection technique.

The Effect of OnabotulinumtoxinA on Aura Frequency and Severity in Patients With Hemiplegic Migraine: Case Series of 11 Patients

BACKGROUND

OnabotulinumtoxinA has been demonstrated to be effective for the preventive treatment of headache in individuals with chronic migraine and has been approved and recommended for this patient population. While the therapeutic effect of onabotulinumtoxinA on migraine headache is well documented, there is limited information on the effect of onabotulinumtoxinA on migraine aura.

OBJECTIVE

Given the prolonged and often debilitating nature of aura in patients with hemiplegic migraine, our group sought to examine the effect of onabotulinumtoxinA on aura frequency and severity in this specific subset of migraine patients.

METHODS

All clinical notes from July 1, 1994 to December 1, 2017 at our institution were retrospectively reviewed to identify patients diagnosed with hemiplegic migraine who received at least one set of onabotulinumtoxinA injections. Thirty-four patients were identified; and of those, 23 were excluded due to incomplete documentation regarding aura symptoms at follow-up visits. The clinical notes of the remaining 11 patients (4 with familial hemiplegic migraine [FHM] and 7 with sporadic hemiplegic migraine [SHM]) were reviewed, and the frequency and description of their headaches and aura before and after receiving onabotulinumtoxinA were recorded.

RESULTS

Nine of the 11 patients in our series noted a decrease in the frequency, severity, and/or duration of their aura after receiving onabotulinumtoxinA. Of the 2 non-responders, one was FHM and one was SHM. Of the 9 that noticed improved aura symptoms, 6 described a "wearing off" effect of onabotulinumtoxinA around week 9 or 10 of the 12-week cycle, with subsequent improvement after the next round.

CONCLUSION

For 9 of 11 patients with hemiplegic migraine, onabotulinumtoxinA was helpful not only in reducing the frequency and severity of headaches but also in reducing the frequency and severity of the aura. In this manuscript, we speculate on potential pathophysiologic mechanisms that could have contributed to this effect.

Botulinum toxin: A review of the mode of action in migraine

Botulinum toxin serotype A (BoNT/A) was originally used in neurology for the treatment of dystonia and blepharospasms, but is now clinically used worldwide for the treatment of chronic migraine. Still, the possible mode of action of BoNT/A in migraine is not fully known. However, the mode of action of BoNT/A has been investigated in experimental pain as well as migraine models, which may elucidate the underlying mechanisms in migraine. The aim of this study was to review studies on the possible mode of action of BoNT/A in relation to chronic migraine treatment. Observations suggest that the mode of action of BoNT/A may not be limited to the injection site, but also includes anatomically connected sites due to axonal transport. The mechanisms behind the effect of BoNT/A in chronic migraine may also include modulation of neurotransmitter release, changes in surface expression of receptors and cytokines as well as enhancement of opioidergic transmission. Clinical and experimental studies with botulinum toxin in the last decade have advanced our understanding of headache and other pain states. More research into botulinum toxin as treatment for headache is warranted as it can be an attractive alternative for patients who do not respond positively to other drugs.

Current Prophylactic Medications for Migraine and Their Potential Mechanisms of Action

A relatively high number of different medications is currently used for migraine prevention in clinical practice. Although these compounds were initially developed for other indications and differ in their mechanisms of action, some general themes can be identified from the mechanisms at play. Efficacious preventive drugs seem to either suppress excitatory nervous signaling via sodium and/or calcium receptors, facilitate GABAergic inhibition, reduce neuronal sensitization, block cortical spreading depression and/or reduce circulating levels of CGRP. We here review such mechanisms for the different compounds.

OnabotulinumtoxinA: A Review in the Prevention of Chronic Migraine

An intramuscular formulation of onabotulinumtoxinA (onabotA; Botox®) is currently the only therapy specifically approved for the prevention of headaches in adults with chronic migraine (CM) in the EU and North America. This article provides a narrative review of relevant data on the drug in this indication from an EU perspective. OnabotA was originally approved on the basis of pooled data from two phase III studies (PREEMPT 1 and 2). In these pivotal studies, injection of up to five cycles of onabotA (155-195 U/cycle) at 12-week intervals was generally well tolerated and effective in producing statistically significant and clinically meaningful improvements in headache symptoms, acute headache pain medication usage, headache impact and health-related quality of life in adults with CM, of whom approximately two-thirds were acute medication overusers and approximately one-third had failed to respond to ≥ 3 prior oral prophylactic therapies. More recently, the efficacy and tolerability of onabotA over a period of 1 year in the PREEMPT programme has been substantiated and extended by the results of a long-term phase IV study (COMPEL), in which patients received up to nine treatment cycles over a period of 2 years, and by findings from several real-world clinical practice studies from Europe, including the prospective multinational REPOSE and CM-PASS studies. In conclusion, the totality of evidence from clinical trials and real-world studies indicates that onabotA is an effective and generally well tolerated option for the prevention of CM that may be particularly useful for patients who have previously failed to respond to or are intolerant of commonly prescribed oral prophylactics.

An academic debate: OnabotulinumtoxinA for chronic migraine: PREEMPT-derived vs "customized" dosing/injection paradigm

In 2010 onabotulinumtoxinA (OnabotA) was approved by the United States Food and Drug Administration for the treatment of chronic migraine (CM). Data supporting approval were derived primarily from two parallel placebo-controlled trials, the PREEMPT studies. Many clinicians and research investigators critical of those data have recommended that the dosing/injection paradigm for treating CM be "customized" to the needs of the individual patient rather than administered in a uniform fashion conforming to the methodology utilized in the PREEMPT studies. In this paper the authors debate the issue of whether treatment of CM with OnabotA should be standardized versus customized.

Neurogenic inflammation and its role in migraine

The etiology of migraine pain involves sensitized meningeal afferents that densely innervate the dural vasculature. These afferents, with their cell bodies located in the trigeminal ganglion, project to the nucleus caudalis, which in turn transmits signals to higher brain centers. Factors such as chronic stress, diet, hormonal fluctuations, or events like cortical spreading depression can generate a state of "sterile inflammation" in the intracranial meninges resulting in the sensitization and activation of trigeminal meningeal nociceptors. This sterile inflammatory phenotype also referred to as neurogenic inflammation is characterized by the release of neuropeptides (such as substance P, calcitonin gene related peptide) from the trigeminal innervation. This release leads to vasodilation, plasma extravasation secondary to capillary leakage, edema, and mast cell degranulation. Although neurogenic inflammation has been observed and extensively studied in peripheral tissues, its role has been primarily investigated in the genesis and maintenance of migraine pain. While some aspects of neurogenic inflammation has been disregarded in the occurrence of migraine pain, targeted analysis of factors have opened up the possibilities of a dialogue between the neurons and immune cells in driving such a sterile neuroinflammatory state in migraine pathophysiology.

Evidence and experience with onabotulinumtoxinA in chronic migraine: Recommendations for daily clinical practice

OnabotulinumtoxinA has been demonstrated to be effective as a preventive treatment in patients with chronic migraine (CM). Five years after the approval of onabotulinumtoxinA in Spain, the Headache Study Group of the Spanish Society of Neurology considered it worthwhile to gather a group of experts in treating patients with CM in order to draw up, based on current evidence and our own experience, a series of guidelines aimed at facilitating the use of the drug in daily clinical practice. For this purpose, we posed 12 questions that we ask ourselves as doctors, and which we are also asked by our patients. Each author responded to one question, and the document was then reviewed by everyone. We hope that this review will constitute a practical tool to help neurologists treating patients with CM.

Role of central versus peripheral opioid system in antinociceptive and anti-inflammatory effect of botulinum toxin type A in trigeminal region

BACKGROUND

Although botulinum toxin type A (BT-A) is approved for chronic migraine treatment, its site and mechanism of action are still elusive. Recently our group discovered that suppression of CGRP release from dural nerve endings might account for antimigraine action of pericranially injected BT-A. We demonstrated that central antinociceptive effect of BT-A in sciatic region involves endogenous opioid system as well. Here we investigated possible interaction of BT-A with endogenous opioid system within the trigeminal region.

METHODS

In orofacial formalin test we investigated the influence of centrally acting opioid antagonist naltrexone (2 mg/kg, s.c.) versus peripherally acting methylnaltrexone (2 mg/kg, s.c.) on BT-A's (5 U/kg, s.c. into whisker pad) or morphine's (6 mg/kg, s.c.) antinociceptive effect and the effect on dural neurogenic inflammation (DNI). DNI was assessed by Evans blue-plasma protein extravasation.

RESULTS

Naltrexone abolished the effect of BT-A on pain and dural plasma protein extravasation, whereas peripherally acting methylnaltrexone did not change either BT-A's effect on pain or its effect on dural extravasation. Naltrexone abolished the antinociceptive and anti-inflammatory effects of morphine, as well. However, methylnaltrexone decreased the antinociceptive effect of morphine only partially in the second phase of the test and had no significant effect on morphine-mediated reduction in DNI.

CONCLUSIONS

Morphine acts on pain in trigeminal region both peripherally and centrally, whereas the effect on dural plasma protein extravasation seems to be only centrally mediated. However, the interaction of BT-A with endogenous opioid system, with consequent inhibition of nociceptive transmission as well as the DNI, occurs primarily centrally.

SIGNIFICANCE

Botulinum toxin type A (BT-A)'s axonal transport and potential transcytosis suggest that its antinociceptive effect might involve diverse neurotransmitters at different sites of trigeminal system. Here we discovered that the reduction in pain and accompanying DNI involves the interaction of BT-A with central endogenous opioid system (probably at the level of trigeminal nucleus caudalis).

Insights into the Functional Anatomy Behind the PREEMPT Injection Paradigm: Guidance on Achieving Optimal Outcomes

OBJECTIVE

To provide clinically relevant insights on the identification of the muscles and techniques involved in the safe and effective use of onabotulinumtoxinA for chronic migraine prophylaxis.

BACKGROUND

Although guidance on the use of onabotulinumtoxinA for chronic migraine is available, based on the Phase III Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical program, clinical experience has shown that insufficient understanding of the anatomy and function of the head and neck muscles may lead to undesirable outcomes and suboptimal efficacy.

DESIGN/METHODS

Each muscle involved in the standardized PREEMPT injection paradigm is reviewed with a thorough description of each muscle's anatomy (ie, muscle description and location, innervation, vascular supply) and function. Key insights based on clinical experience are also provided to help improve outcomes.

RESULTS

The identification of the muscles in the PREEMPT injection paradigm should be based on each patient's unique anatomy and injections should be administered using the advised techniques. A thorough examination of the patient prior to treatment is also critical to determine if any preexisting conditions may increase the risk for unwanted outcomes and appropriate expectations should be communicated.

CONCLUSIONS

Thorough knowledge of the functional anatomy of the muscles involved in the standardized PREEMPT injection paradigm is critical to achieve the efficacy and safety observed in clinical trials. In addition, it is important to assess a patient's baseline condition to anticipate the risk for unwanted outcomes that may result from treatment.

Botulinum neurotoxin type A-cleaved SNAP25 is confined to primary motor neurons and localized on the plasma membrane following intramuscular toxin injection

The mechanism of action of botulinum neurotoxin type A (BoNT/A) is well characterized, but some published evidence suggests the potential for neuronal retrograde transport and cell-to-cell transfer (transcytosis) under certain experimental conditions. The present study evaluated the potential for these processes using a highly selective antibody for the BoNT/A-cleaved substrate (SNAP25₁₉₇) combined with 3-dimensional imaging. SNAP25₁₉₇ was characterized in a rat motor neuron (MN) pathway following toxin intramuscular injections at various doses to determine whether SNAP25₁₉₇ is confined to MNs or also found in neighboring cells or nerve fibers within spinal cord (SC). Results demonstrated that SNAP25₁₉₇ immuno-reactive staining was colocalized with biomarkers for MNs, but not with markers for neighboring neurons, nerve fibers or glial cells. Additionally, a high dose of BoNT/A, but not a lower dose, resulted in sporadic SNAP25₁₉₇ signal in distal muscles and associated SC regions without evidence for transcytosis, suggesting that the staining was due to systemic spread of the toxin. Despite this spread, functional effects were not detected in the distal muscles. Therefore, under the present experimental conditions, our results suggest that BoNT/A is confined to MNs and any evidence of distal activity is due to limited systemic spread of the toxin at higher doses and not through transcytosis within SC. Lastly, at higher doses of BoNT/A, SNAP25₁₉₇ was expressed throughout MNs and colocalized with synaptic markers on the plasma membrane at 6 days post-treatment. These data support previous studies suggesting that SNAP25₁₉₇ may be incorporated into SNARE-protein complexes within the affected MNs.

Targeted Peripheral Nerve-directed Onabotulinumtoxin A Injection for Effective Long-term Therapy for Migraine Headache

Background:

Onabotulinumtoxin A (BOTOX) is an FDA-approved treatment for chronic migraine headaches (MHs) that involves on-label, high-dose administration across 31 anatomic sites. Anatomically specific peripheral nerve trigger sites have been identified that contribute to MH pathogenesis and are amenable to both BOTOX injection and surgical decompression. These sites do not always correlate with the on-label FDA-approved injection pattern, but represent a more targeted approach. The efficacy of peripheral nerve–directed BOTOX injection as an independent long-term therapeutic option has not been investigated.

Methods:

The technique for peripheral nerve–directed therapeutic long-term BOTOX injection is described. A retrospective review was subsequently completed for 223 patients with MH. Sixty-six patients elected to proceed with diagnostic BOTOX injections. Of these, 24 continued long-term therapeutic BOTOX injections, whereas 42 matriculated to surgery. Outcomes were tracked.

Results:

Initial outcomes included significant improvement in migraine headache index (MHI) (53.5 ± 83.0, P < 0.006), headache days/mo (9.2 ± 12.7, P < 0.0009), and migraine severity (2.6 ± 2.5, P < 0.00008) versus baseline. MHI improved from the initiation of diagnostic injections to the establishment of steady-state injections (P < 0.002), and further improved over time (P < 0.05, mean follow-up 615 days) with no desensitization observed. Decompressive surgery resulted in significant improvement in MHI (100.8 ± 109.7, P < 0.0000005), headache days/mo (10.8 ± 12.7, P < 0.000002), migraine severity (3.0 ± 3.8, P < 0.00001), and migraine duration in hours (16.8 ± 21.6, P < 0.0007). MHI improvement with surgery was better than long-term BOTOX injections (P < 0.05).

Conclusions:

Though inferior to surgical decompression, preliminary data demonstrate that targeted peripheral nerve–directed BOTOX injection is an effective primary therapy for MH representing a possible alternative to nondirected BOTOX injection with decreased dosage requirements and potentially decreased cost.

A novel therapeutic with two SNAP-25 inactivating proteases shows long-lasting anti-hyperalgesic activity in a rat model of neuropathic pain

A pressing need exists for long-acting, non-addictive medicines to treat chronic pain, a major societal burden. Botulinum neurotoxin type A (BoNT/A) complex - a potent, specific and prolonged inhibitor of neuro-exocytosis - gives some relief in several pain disorders, but not for all patients. Our study objective was to modify BoNT/A to overcome its inability to block transmitter release elicited by high [Ca²⁺]_i and increase its limited analgesic effects. This was achieved by fusing a BoNT/A gene to that for the light chain (LC) of type/E. The resultant purified protein, LC/E-BoNT/A, entered cultured sensory neurons and, unlike BoNT/A, inhibited release of calcitonin gene-related peptide evoked by capsaicin. Western blotting revealed that this improvement could be due to a more extensive truncation by LC/E of synaptosomal-associated protein of Mr = 25 k, essential for neuro-exocytosis. When tested in a rat spared nerve injury (SNI) model, a single intra-plantar (IPL) injection of LC/E-BoNT/A alleviated for ∼2 weeks mechanical and cold hyper-sensitivities, in a dose-dependent manner. The highest non-paralytic dose (75 U/Kg, IPL) proved significantly more efficacious than BoNT/A (15 U/Kg, IPL) or repeated systemic pregabalin (10 mg/Kg, intraperitoneal), a clinically-used pain modulator. Effects of repeated or delayed injections of this fusion protein highlighted its analgesic potential. Attenuation of mechanical hyperalgesia was extended by a second administration when the effect of the first had diminished. When injected 5 weeks after injury, LC/E-BoNT/A also reversed fully-established mechanical and cold hyper-sensitivity. Thus, combining advantageous features of BoNT/E and/A yields an efficacious, locally-applied and long-acting anti-hyperalgesic.

Chronic Migraine: An Update on Physiology, Imaging, and the Mechanism of Action of Two Available Pharmacologic Therapies

Several lines of research support the hypothesis that migraine is a spectrum of illness, with clinical symptoms that vary along a continuum from episodic migraine to chronic migraine. Physiologic changes may result in episodic migraine evolving into chronic migraine over months to years in susceptible individuals. With chronification, headache frequency increases, becoming more disabling and less responsive to therapy. Neurophysiologic and functional imaging research has reported that chronic migraine may be associated with severity‐specific metabolic, functional, and structural abnormalities in the brainstem. Without longitudinal studies, it is unclear whether these changes may represent a continuum of individual progression and/or are reversible. Furthermore, chronic migraine is associated with larger impairments in cortical processing of sensory stimuli when compared with episodic migraine, possibly caused by more pronounced cortical hyperexcitability.

Progressive changes in nociceptive thresholds and subsequent central sensitization due to recurrent migraine attacks in vulnerable individuals contribute to the chronic migraine state. This may result in changes to baseline neurologic function between headache attacks, evident in both electrophysiological and functional imaging research. Patients experiencing migraine chronification may report increased non‐headache pain, fatigue, psychiatric disorders (eg, depression, anxiety), gastrointestinal complaints, and other somatic conditions associated with their long‐term experience with migraine pain.

Recent research provides a foundation for differentiating episodic and chronic migraine based on neurophysiologic and neuroimaging tools. In this literature review, we consider these findings in the context of models designed to explain the physiology and progression of episodic migraine into chronic migraine, and consider treatment of chronic migraine in susceptible individuals. Advances in pharmacotherapy provide treatment options for chronic migraine. Of the currently available treatment options, only onabotulinumtoxinA and topiramate have received regulatory approval and have demonstrated efficacy in patients with chronic migraine, although the exact mechanisms of action are not fully elucidated.

Trigeminal nervous system sensitization by infraorbital nerve injury enhances responses in a migraine model

Background

Although the peripheral and central sensitizations of trigeminal nervous system may be one of the important factors of migraine, the precise mechanism is not fully understood. In this study, we examined the influence of the sensitization of the second division of the trigeminal nerve (V2) by chronic constriction injury (CCI) of the infraorbital nerve (ION) on migraine headache, using the capsaicin-induced migraine model.

Methods

Male Sprague-Dawley rats were assigned to four groups: (a) sham surgery and topical-dural vehicle application (Sham + Vehicle) group, (b) CCI-ION and topical-dural vehicle application (CCI-ION + Vehicle) group, (c) sham surgery and topical-dural capsaicin application (Sham + Capsaicin) group, (d) CCI-ION and topical-dural capsaicin application (CCI-ION + Capsaicin) group. Behavioral testing and immunohistochemical staining were performed.

Results

In the behavioral test, the Sham + Capsaicin group showed significantly longer duration of immobilization and shorter duration of exploration compared with the Sham + Vehicle group, which is similar to clinical features of migraine patients. Moreover, CCI-ION enhanced these effects in the CCI-ION + Capsaicin group. Immunohistochemical staining for phospho-extracellular signal-related kinase (pERK) in the trigeminal ganglion (TG) containing first and second divisions of the trigeminal nerve and the trigeminocervical complex (TCC) revealed that pERK expression was significantly increased in the CCI-ION + Capsaicin group compared with the other groups. However, comparing between effects of the peripheral and central sensitizations (in the TG and TCC), from our results, peripheral sensitization would play a much less or not significant role.

Conclusions

These data demonstrate that the sensitization of V2 could influence the activation and the sensitization of the first division of the trigeminal nerve in the TCC, subsequently exacerbating pain sensation and pain-related behaviors. We have shown for the first time that the existence of the central sensitization of V2 can be an exacerbating factor for migraine related nociceptive thresholds/activation.

Brain Changes in Responders vs. Non-Responders in Chronic Migraine: Markers of Disease Reversal

The aim of this study was to identify structural and functional brain changes that accompanied the transition from chronic (CM; ≥15 headache days/month) to episodic (EM; <15 headache days/month) migraine following prophylactic treatment with onabotulinumtoxinA (BoNT-A). Specifically, we examined whether CM patients responsive to prophylaxis (responders; n = 11), as evidenced by a reversal in disease status (defined by at least a 50% reduction in migraine frequency and <15 headache days/month), compared to CM patients whose migraine frequency remained unchanged (non-responders; n = 12), showed differences in cortical thickness using surface-based morphometry. We also investigated whether areas showing group differences in cortical thickness displayed altered resting-state functional connectivity (RS-FC) using seed-to-voxel analyses. Migraine characteristics measured across groups included disease duration, pain intensity and headache frequency. Patient reports of headache frequency over the 4 weeks prior to (pre-treatment) and following (post-treatment) prophylaxis were compared (post minus pre) and this measure served as the clinical endpoint that determined group assignment. All patients were scanned within 2 weeks of the post-treatment visit. Results revealed that responders showed significant cortical thickening in the right primary somatosensory cortex (SI) and anterior insula (aINS), and left superior temporal gyrus (STG) and pars opercularis (ParsOp) compared to non-responders. In addition, disease duration was negatively correlated with cortical thickness in fronto-parietal and temporo-occipital regions in responders but not non-responders, with the exception of the primary motor cortex (MI) that showed the opposite pattern; disease duration was positively associated with MI cortical thickness in responders versus non-responders. Our seed-based RS-FC analyses revealed anti-correlations between the SI seed and lateral occipital (LOC) and dorsomedial prefrontal cortices (DMPFC) in responders, whereas non-responders showed increased connectivity between the ParsOp seed and LOC. Overall, our findings revealed distinct morphometric and functional brain changes in CM patients that reverted to EM following prophylactic treatment compared to CM patients that showed no change in disease status. Elucidating the CNS changes involved in disease reversal may be critical to discovering interventions that prevent or slow the progression of CM. Such changes may aid in the evaluation of treatments as well as provide markers for disease “de-chronification”.