Anatomy and Physiology of Pain Referral Patterns in Primary and Cervicogenic Headache Disorders

Pituitary cyclase-activating polypeptide targeted treatments for the treatment of primary headache disorders

OBJECTIVE

Migraine is a complex and disabling neurological disorder. Recent years have witnessed the development and emergence of novel treatments for the condition, namely those targeting calcitonin gene-related peptide (CGRP). However, there remains a substantial need for further treatments for those unresponsive to current therapies. Targeting pituitary adenylate cyclase-activating polypeptide (PACAP) as a possible therapeutic strategy in the primary headache disorders has gained interest over recent years.

METHODS

This review will summarize what we know about PACAP to date: its expression, receptors, roles in migraine and cluster headache biology, insights gained from preclinical and clinical models of migraine, and therapeutic scope.

RESULTS

PACAP shares homology with vasoactive intestinal polypeptide (VIP) and is one of several vasoactive neuropeptides along with CGRP and VIP, which has been implicated in migraine neurobiology. PACAP is widely expressed in areas of interest in migraine pathophysiology, such as the thalamus, trigeminal nucleus caudalis, and sphenopalatine ganglion. Preclinical evidence suggests a role for PACAP in trigeminovascular sensitization, while clinical evidence shows ictal release of PACAP in migraine and intravenous infusion of PACAP triggering attacks in susceptible individuals. PACAP leads to dural vasodilatation and secondary central phenomena via its binding to different G-protein-coupled receptors, and intracellular downstream effects through cyclic adenosine monophosphate (cAMP) and phosphokinase C (PKC). Targeting PACAP as a therapeutic strategy in headache has been explored using monoclonal antibodies developed against PACAP and against the PAC1 receptor, with initial positive results.

INTERPRETATION

Future clinical trials hold considerable promise for a new therapeutic approach using PACAP-targeted therapies in both migraine and cluster headache.

Four Decades of Occipital Nerve Stimulation for Headache Disorders: A Systematic Review

PURPOSE OF REVIEW

Chronic headaches are a significant source of disability worldwide. Despite the development of conventional strategies, a subset of patients remain refractory and/or experience side effects following these treatments. Hence, occipital nerve stimulation (ONS) should be considered as an alternative strategy for intractable chronic headaches. This review aims to provide a comprehensive overview of the effectiveness, safety, mechanisms and practical application of ONS for the treatment of headache disorders.

RECENT FINDINGS

Overall response rate of ONS is 35.7-100%, 17-100%, and 63-100% in patients with cluster headache, chronic migraine and occipital neuralgia respectively. Regarding the long-term effectivity in all groups, 41.6-88.0% of patients remain responders after ≥ 18.3 months. The most frequently reported adverse events include lead migration/fracture (13%) and local pain (7.3%). Based on our results, ONS can be considered a safe and effective treatment for chronic intractable headache disorders. To support more widespread application of ONS, additional research with larger sample sizes should be conducted.

Review of craniofacial pain syndromes involving the greater occipital nerve: relevant anatomy, clinical findings, and interventional management

Craniofacial pain syndromes exhibit a high prevalence in the general population, with a subset of patients developing chronic pain that significantly impacts their quality of life and results in substantial disabilities. Anatomical and functional assessments of the greater occipital nerve (GON) have unveiled its implication in numerous craniofacial pain syndromes, notably through the trigeminal-cervical convergence complex. The pathophysiological involvement of the greater occipital nerve in craniofacial pain syndromes, coupled with its accessibility, designates it as the primary target for various interventional procedures in managing craniofacial pain syndromes. This educational review aims to describe multiple craniofacial pain syndromes, elucidate the role of GON in their pathophysiology, detail the relevant anatomy of the greater occipital nerve (including specific intervention sites), highlight the role of imaging in diagnosing craniofacial pain syndromes, and discuss various interventional procedures such as nerve infiltration, ablation, neuromodulation techniques, and surgeries. Imaging is essential in managing these patients, whether for diagnostic or therapeutic purposes. The utilization of image guidance has demonstrated an enhancement in reproducibility, as well as technical and clinical outcomes of interventional procedures. Studies have shown that interventional management of craniofacial pain is effective in treating occipital neuralgia, cervicogenic headaches, cluster headaches, trigeminal neuralgia, and chronic migraines, with a reported efficacy of 60-90% over a duration of 1-9 months. Repeated infiltrations, neuromodulation, or ablation may prove effective in selected cases. Therefore, reassessment of treatment response and efficacy during follow-up is imperative to guide further management and explore alternative treatment options. Optimal utilization of imaging, interventional techniques, and a multidisciplinary team, including radiologists, will ensure maximum benefit for these patients.

[Complementary and supplementary procedures in the treatment of headache]

In Germany, headache is one of the illnesses that most frequently leads to health impairments and to consultation with physicians. Even in children, headache is often associated with restricted activities of daily life. Nevertheless, the level of care for headache disorders is disproportionate to the medical needs. As a result, patients regularly use complementary and supportive therapeutic procedures. This review shows the procedures currently used for primary headache in childhood and adulthood, the methodological approaches and existing scientific evidence. The safety of the therapeutic options is also classified. These methods include physiotherapy, neural therapy, acupuncture, homeopathy, phytotherapy and the intake of dietary supplements. For children and adolescents with headaches, there are studies in the field of dietary supplements for coenzyme Q10, riboflavin, magnesium and vitamin D, which indicate specific effects in the reduction of headaches.

An Update on Temporomandibular Disorders (TMDs) and Headache

PURPOSE OF REVIEW

To provide an overview and highlight recent updates in temporomandibular disorders (TMDs) and their comorbidity with headache disorders regarding pathophysiology and management.

RECENT FINDINGS

In the last decade, there have been great advancements in the understanding of TMDs and their relationship with neurovascular pains such as headaches. Understanding of TMDs is necessary for the context of its comorbidity with primary headache disorders. The literature regarding management of these comorbidities is scarce but points to combination therapy including pharmacological and non-pharmacological approaches to optimize management. The use of CGRP receptor-targeted monoclonal antibodies or CGRP receptor antagonists should be explored for the management of chronic TMDs. It could also be used as a novel monotherapy or in combination with non-pharmacological approaches for TMDs' comorbidity with headache, particularly migraine. Research is needed to support evidence-based management protocols. A team involving neurology (headache medicine) and dentistry (orofacial pain) is critical for optimal management.

Pharmacological Management of Orofacial Pain

Orofacial pain is a category of complex disorders, including musculoskeletal, neuropathic and neurovascular disorders, that greatly affect the quality of life of the patient. These disorders are within the fields of dentistry and medicine and management can be challenging, requiring a referral to an orofacial pain specialist, essential for adequate evaluation, diagnosis, and care. Management is specific to the diagnosis and a treatment plan is developed with diverse pharmacological and non-pharmacological modalities. The pharmacological management of orofacial pain encompasses a vast array of medication classes and approaches. This includes anti-inflammatory drugs, muscle relaxants, anticonvulsants, antidepressants, and anesthetics. In addition, as adjunct therapy, different injections can be integrated into the management plan depending on the diagnosis and needs. These include trigger point injections, temporomandibular joint (TMJ) injections, and neurotoxin injections with botulinum toxin and nerve blocks. Multidisciplinary management is key for optimal care. New and safer therapeutic targets exclusively for the management of orofacial pain disorders are needed to offer better care for this patient population.

Occipital Nerve Stimulation: An Alternative Treatment of Chronic Migraine

PURPOSE OF REVIEW

This paper will examine the efficacy and safety of occipital nerve stimulation as a non-pharmacological alternative treatment for migraine.

RECENT FINDINGS

Migraine is characterized as a primary headache disorder with possible premonitory and aura phases, both of which vary greatly in symptomatology. The most common treatments for chronic migraine are pharmacological and are aimed at both acute relief (e.g., nonsteroidal anti-inflammatory drugs, triptans, and ergots) and prophylaxis (e.g., propranolol, valproic acid, and topiramate). For patients with medically refractory migraine, acute relief medication overuse can increase the risk of developing more severe and more frequent migraine attacks. Occipital nerve stimulation is a non-pharmacological alternative treatment for chronic migraine, which could eliminate the risk of adverse effects from acute relief medication overuse. Neurostimulation is thought to prevent pain by blocking signal transduction from small nociceptive fibers with non-painful signaling in larger adjacent fibers. Existing data from clinical trials support the overall safety and efficacy of occipital nerve stimulation for the treatment of chronic migraine. However, few large controlled, double-blinded studies have been conducted, due to both practical and ethical concerns. Currently, occipital nerve stimulation is available as an off-label use of neurostimulation for pain prevention but is not approved by the FDA specifically for the treatment of chronic migraine.

Increased migraine-free intervals with multifocal repetitive transcranial magnetic stimulation

INTRODUCTION

Episodic migraine is a debilitating condition associated with vast impairments of health, daily living, and life quality. Several prophylactic treatments exist, having a moderate ratio of action related to side effects and therapy costs. Repetitive transcranial magnetic stimulation (rTMS) is an evidence based therapy in several neuropsychiatric conditions, showing robust efficacy in alleviating specific symptoms. However, its efficacy in migraine disorders is unequivocal and might be tightly linked to the applied rTMS protocol. We hypothesized that multifocal rTMS paradigm could improve clinical outcomes in patients with episodic migraine by reducing the number of migraine days, frequency and intensity of migraine attacks, and improve the quality of life.

METHODS

We conducted an experimental, double-blind, randomized controlled study by applying a multifocal rTMS paradigm. Patients with episodic migraine with or without aura were enrolled in two centers from August 2018, to December 2019, and randomized to receive either real (n = 37) or sham (sham coil stimulation, n = 28) multifocal rTMS for six sessions over two weeks. Patients, physicians, and raters were blinded to the applied protocol. The experimental multifocal rTMS protocol included two components; first, swipe stimulation of 13 trains of 140 pulses/train, 67 Hz, 60% of RMT, and 2s intertrain interval and second, spot burst stimulation of 33 trains of 15 pulses/train, 67 Hz, 85% of RMT, and 8s intertrain interval. Reduction >50% from the baseline in migraine days (as primary outcome) and frequency and intensity of migraine attacks (as key secondary outcomes) over a 12-week period were assessed. To balance the baseline variables between the treatment arms, we applied the propensity score matching through the logistic regression.

RESULTS

Among 65 randomized patients, sixty (age 39.7 ± 11.6; 52 females; real rTMS n = 33 and sham rTMS n = 27) completed the trial and five patients dropped out. Over 12 weeks, the responder's rate in the number of migraine days was significantly higher in the real rTMS compared to the sham group (42% vs. 26%, p < 0.05). The mean migraine days per month decreased from 7.6 to 4.3 days in the real rTMS group and from 6.2 to 4.3 days in the sham rTMS group, resulting in a difference with real vs. sham rTMS of -3.2 days (p < 0.05). Similarly, over the 12-week period, the responder's rate in the reduction of migraine attacks frequency was higher in the real rTMS compared to the sham group (42% vs 33%, p < 0.05). No serious adverse events were observed.

CONCLUSION

Our pilot study shows compelling evidence in a double placebo-controlled trial that multifocal rTMS is an effective and well-tolerated preventive treatment in patients with episodic migraine.

MRI in migraineurs: are there abnormalities in the area where the myofascial trigger points are palpable and in volume measurements?

INTRODUCTION

Patients with migraine may present a higher quantity of myofascial trigger points (MTrP) and alterations in the cervical muscles when compared to non-migraineurs. The magnetic resonance imaging (MRI) is a robust method for the study of human soft tissues and could be useful to investigate these points.

OBJECTIVES

To identify the presence of MTrP in the descending fibers of the trapezius muscle in women with migraine and to quantify the muscle volume by MRI, correlating it with the headache characteristics.

METHODS

A cross-sectional analytic study was conducted among 14 women, eight in migraine group, and six in without migraine group. The presence of MTrP was evaluated using Simons' criteria, and linolenic acid capsules subsequently marked the areas. MRI was performed with 1.5T, T1-weighted sequence, and T2 in the axial, sagittal, and coronal planes. The T1-weighted sequences were performed with and without gadolinium contrast.

RESULTS

The T1-weighted image analysis with and without gadolinium did not show any signal alteration in the MTrP areas in both groups. The migraine group presented more MTrP in the trapezius muscle (MD [95%CI] = 1[1; 3]; MD [95%CI] = 1[0; 2] right and left side, respectively), and a smaller muscle volume (MD [95%CI] = -198.1[-338.7;-25.6], MD [95%CI] = -149.9[-325.05;-0.13] right and left side, respectively) than non-migraineurs. The migraine frequency presented a negative strong correlation with the trapezius volumes (r = -0.812; p = 0.014).

CONCLUSION

Migraineurs present more MTrP and a smaller muscle volume than non-migraineurs. The trapezius volume is negatively correlated with migraine frequency. MRI is not a suitable outcome measure for assessing MTrP.

Contract-relax technique compared to static stretching in treating migraine in women: A randomized pilot trial

INTRODUCTION

Physical therapy is often used by patients with headache, including modalities such as muscle stretching exercises.

OBJECTIVES

To evaluate the feasibility of a pilot trial aimed at determining the efficacy of the proprioceptive neuromuscular facilitation (PNF) contract-relax technique compared to static stretching for treating migraineurs.

METHODS

This pilot trial allocated 30 migraineur women (23 ± 4 years) into PNF (n = 15) and static stretching groups (n = 15). The interventions were performed twice a week (16 sessions, 8 weeks). The feasibility outcomes included successful random allocation of 30 patients during a 12-month period, the proportion of eligible patients randomly assigned to each group, and the proportion of those who completed the 30-day follow-up. The outcomes of headache characteristics; medication intake; severity of migraine-related disability; neck disability; cervical mobility; pressure pain threshold; adverse effects and global perception of change were evaluated at baseline, after the end of treatment and after 30-day follow-up.

RESULTS

The recruitment rate was 4.66% participants/month. The proportion of eligible patients randomly assigned to each group and for those who completed the 30-day follow-up was 88.23% and 100%, respectively. Both groups improved in headache-related outcomes. The perception of change was important for 67% of the PNF group and 47% of the static stretching group. No differences were found between groups regarding the studied outcomes.

CONCLUSION

This is a feasible pilot trial. The PNF contract-relax technique was no more effective than static stretching for treating migraine, but both techniques improved the headache, the severity of migraine-related disability and the satisfaction after treatment.

Facial Pain: A Comprehensive Review and Proposal for a Pragmatic Diagnostic Approach

BACKGROUND

Facial pain, alone or combined with other symptoms, is a frequent complaint. Moreover, it is a symptom situated at, more than any other pain condition, a crosspoint where several disciplines meet, for example, dentists; manual therapists; ophthalmologists; psychologists; and ear-nose-throat, pain, and internal medicine physicians besides neurologists and neurosurgeons. Recently, a new version of the most widely used classification system among neurologists for headache and facial pain, the International Classification of Headache Disorders, has been published.

OBJECTIVE

The aims of this study were to provide an overview of the most prevalent etiologies of facial pain and to provide a generic framework for the neurologist on how to manage patients presenting with facial pain.

METHODS

An overview of the different etiologies of facial pain is provided from the viewpoint of the respective clinical specialties that are confronted with facial pain. Key message: Caregivers should "think outside their own box" and refer to other disciplines when indicated. If not, a correct diagnosis can be delayed and unnecessary treatments might be given. The presented framework is aimed at excluding life- or organ-threatening diseases, providing several clinical clues and indications for technical investigations, and ultimately leading to the correct diagnosis and/or referral to other disciplines.

Emerging evidence of occipital nerve compression in unremitting head and neck pain

Unremitting head and neck pain (UHNP) is a commonly encountered phenomenon in Headache Medicine and may be seen in the setting of many well-defined headache types. The prevalence of UHNP is not clear, and establishing the presence of UHNP may require careful questioning at repeated patient visits. The cause of UHNP in some patients may be compression of the lesser and greater occipital nerves by the posterior cervical muscles and their fascial attachments at the occipital ridge with subsequent local perineural inflammation. The resulting pain is typically in the sub-occipital and occipital location, and, via anatomic connections between extracranial and intracranial nerves, may radiate frontally to trigeminal-innervated areas of the head. Migraine-like features of photophobia and nausea may occur with frontal radiation. Occipital allodynia is common, as is spasm of the cervical muscles. Patients with UHNP may comprise a subgroup of Chronic Migraine, as well as of Chronic Tension-Type Headache, New Daily Persistent Headache and Cervicogenic Headache. Centrally acting membrane-stabilizing agents, which are often ineffective for CM, are similarly generally ineffective for UHNP. Extracranially-directed treatments such as occipital nerve blocks, cervical trigger point injections, botulinum toxin and monoclonal antibodies directed at calcitonin gene related peptide, which act primarily in the periphery, may provide more substantial relief for UHNP; additionally, decompression of the occipital nerves from muscular and fascial compression is effective for some patients, and may result in enduring pain relief. Further study is needed to determine the prevalence of UHNP, and to understand the role of occipital nerve compression in UHNP and of occipital nerve decompression surgery in chronic head and neck pain.

Neurovascular mechanisms of migraine and cluster headache

Vascular theories of migraine and cluster headache have dominated for many years the pathobiological concept of these disorders. This view is supported by observations that trigeminal activation induces a vascular response and that several vasodilating molecules trigger acute attacks of migraine and cluster headache in susceptible individuals. Over the past 30 years, this rationale has been questioned as it became clear that the actions of some of these molecules, in particular, calcitonin gene-related peptide and pituitary adenylate cyclase-activating peptide, extend far beyond the vasoactive effects, as they possess the ability to modulate nociceptive neuronal activity in several key regions of the trigeminovascular system. These findings have shifted our understanding of these disorders to a primarily neuronal origin with the vascular manifestations being the consequence rather than the origin of trigeminal activation. Nevertheless, the neurovascular component, or coupling, seems to be far more complex than initially thought, being involved in several accompanying features. The review will discuss in detail the anatomical basis and the functional role of the neurovascular mechanisms relevant to migraine and cluster headache.

Brain structure and function related to headache: Brainstem structure and function in headache

OBJECTIVE

To review and discuss the literature relevant to the role of brainstem structure and function in headache.

BACKGROUND

Primary headache disorders, such as migraine and cluster headache, are considered disorders of the brain. As well as head-related pain, these headache disorders are also associated with other neurological symptoms, such as those related to sensory, homeostatic, autonomic, cognitive and affective processing that can all occur before, during or even after headache has ceased. Many imaging studies demonstrate activation in brainstem areas that appear specifically associated with headache disorders, especially migraine, which may be related to the mechanisms of many of these symptoms. This is further supported by preclinical studies, which demonstrate that modulation of specific brainstem nuclei alters sensory processing relevant to these symptoms, including headache, cranial autonomic responses and homeostatic mechanisms.

REVIEW FOCUS

This review will specifically focus on the role of brainstem structures relevant to primary headaches, including medullary, pontine, and midbrain, and describe their functional role and how they relate to mechanisms of primary headaches, especially migraine.

Current and novel insights into the neurophysiology of migraine and its implications for therapeutics

Migraine headache and its associated symptoms have plagued humans for two millennia. It is manifest throughout the world, and affects more than 1/6 of the global population. It is the most common brain disorder, and is characterized by moderate to severe unilateral headache that is accompanied by vomiting, nausea, photophobia, phonophobia, and other hypersensitive symptoms of the senses. While there is still a clear lack of understanding of its neurophysiology, it is beginning to be understood, and it seems to suggest migraine is a disorder of brain sensory processing, characterized by a generalized neuronal hyperexcitability. The complex symptomatology of migraine indicates that multiple neuronal systems are involved, including brainstem and diencephalic systems, which function abnormally, resulting in premonitory symptoms, ultimately evolving to affect the dural trigeminovascular system, and the pain phase of migraine. The migraineur also seems to be particularly sensitive to fluctuations in homeostasis, such as sleep, feeding and stress, reflecting the abnormality of functioning in these brainstem and diencephalic systems. Implications for therapeutic development have grown out of our understanding of migraine neurophysiology, leading to major drug classes, such as triptans, calcitonin gene-related peptide receptor antagonists, and 5-HT1F receptor agonists, as well as neuromodulatory approaches, with the promise of more to come. The present review will discuss the current understanding of the neurophysiology of migraine, particularly migraine headache, and novel insights into the complex neural networks responsible for associated neurological symptoms, and how interaction of these networks with migraine pain pathways has implications for the development of novel therapeutics.

Pathophysiology of Migraine: A Disorder of Sensory Processing

Plaguing humans for more than two millennia, manifest on every continent studied, and with more than one billion patients having an attack in any year, migraine stands as the sixth most common cause of disability on the planet. The pathophysiology of migraine has emerged from a historical consideration of the "humors" through mid-20th century distraction of the now defunct Vascular Theory to a clear place as a neurological disorder. It could be said there are three questions: why, how, and when? Why: migraine is largely accepted to be an inherited tendency for the brain to lose control of its inputs. How: the now classical trigeminal durovascular afferent pathway has been explored in laboratory and clinic; interrogated with immunohistochemistry to functional brain imaging to offer a roadmap of the attack. When: migraine attacks emerge due to a disorder of brain sensory processing that itself likely cycles, influenced by genetics and the environment. In the first, premonitory, phase that precedes headache, brain stem and diencephalic systems modulating afferent signals, light-photophobia or sound-phonophobia, begin to dysfunction and eventually to evolve to the pain phase and with time the resolution or postdromal phase. Understanding the biology of migraine through careful bench-based research has led to major classes of therapeutics being identified: triptans, serotonin 5-HT1B/1D receptor agonists; gepants, calcitonin gene-related peptide (CGRP) receptor antagonists; ditans, 5-HT1F receptor agonists, CGRP mechanisms monoclonal antibodies; and glurants, mGlu5 modulators; with the promise of more to come. Investment in understanding migraine has been very successful and leaves us at a new dawn, able to transform its impact on a global scale, as well as understand fundamental aspects of human biology.

Safety and Efficacy of Occipital Nerves Stimulation for the Treatment of Chronic Migraines: Randomized, Double-blind, Controlled Single-center Experience

BACKGROUND

A recent multicenter study presented 52-week safety and efficacy results from an open-label extension of a randomized, sham-controlled trial for patients with chronic migraine (CM) undergoing peripheral nerve stimulation of the occipital nerves. We present the data from a single center of 20 patients enrolled at the Cleveland Clinic's Pain Management Department.

METHODS

In this single center, 20 patients were implanted with a neurostimulation system, randomized to an active or control group for 12 weeks, and received open-label treatment for an additional 40 weeks. Outcomes collected included number of headache days, pain intensity, Migraine Disability Assessment (MIDAS), Zung Pain and Distress (PAD), direct patient reports of headache pain relief, quality of life, satisfaction, and adverse events (AEs).

RESULTS

Headache days per month were reduced by 8.51 (±9.81) days (P < 0.0001). The proportion of patients who achieved a 30% and 50% reduction in headache days and/or pain intensity was 60% and 35%, respectively. MIDAS and Zung PAD were reduced for all patients. Fifteen (75%) of the 20 patients at the site reported at least one AE. A total of 20 AEs were reported from the site.

CONCLUSION

Our results support the 12-month efficacy of 20 CM patients receiving peripheral nerve stimulation of the occipital nerves in this single-center trial.

Concordant occipital and supraorbital neurostimulation therapy for hemiplegic migraine; initial experience; a case series

INTRODUCTION

Hemiplegic migraine is a particularly severe form of the disease that often evolves to a debilitating chronic illness that is resistant to commonly available therapies. Peripheral neurostimulation has been found to be a beneficial therapy for some patients among several diagnostic classes of migraine, but its potential has not been specifically evaluated for hemiplegic migraine.

MATERIALS AND METHODS

Four patients with hemiplegic migraine were treated with concordant, combined occipital and supraorbital neurostimulation over periods ranging 6-92 months. The clinical indicators followed included assessments of headache frequency and severity, frequency of hemiplegic episodes, functional impairment, medication usage, and patient satisfaction.

RESULTS

All reported a positive therapeutic response, as their average headache frequency decreased by 92% (30 to 2.5 headache days/month); Visual Analog Score by 44% (9.5 to 5.3); frequency of hemiplegic episodes by 96% (7.5 to 0.25 hemiplegic episodes/month); headache medication usage by 96% (6 to 0.25 daily medications); and Migraine Disability Assessment score by 98% (249 to 6). All were satisfied and would recommend the therapy, and all preferred combined occipital-supraorbital neurostimulation to occipital neurostimulation alone.

CONCLUSIONS

Concordant combined occipital and supraorbital neurostimulation may provide effective therapy for both the pain and motor aura in some patients with hemiplegic migraine.

Headache and sleep: shared pathophysiological mechanisms

OBJECTIVE

The objective of the current article is to review the shared pathophysiological mechanisms which may underlie the clinical association between headaches and sleep disorders.

BACKGROUND

The association between sleep and headache is well documented in terms of clinical phenotypes. Disrupted sleep-wake patterns appear to predispose individuals to headache attacks and increase the risk of chronification, while sleep is one of the longest established abortive strategies. In agreement, narcoleptic patients show an increased prevalence of migraine compared to the general population and specific familial sleep disorders have been identified to be comorbid with migraine with aura.

CONCLUSION

The pathophysiology and pharmacology of headache and sleep disorders involves an array of neural networks which likely underlie their shared clinical association. While it is difficult to differentiate between cause and effect, or simply a spurious relationship the striking brainstem, hypothalamic and thalamic convergence would suggest a bidirectional influence.

Pearls and pitfalls in experimental in vivo models of migraine: dural trigeminovascular nociception

BACKGROUND

Migraine is a disorder of the brain and is thought to involve activation of the trigeminovascular system, which includes the peripheral afferent projection to the nociceptive specific dura mater, as well as the central afferent projection to the trigeminal nucleus caudalis. Stimulation of the blood vessels of the dura mater produces pain in patients that is referred to the head similar to headache. HEADACHE MECHANISMS: The likely reason for the pain is because the vascular structures of the dura mater, including the superior sagittal sinus and middle meningeal artery, are richly innervated by a plexus of largely unmyelinated sensory nerve fibers from the ophthalmic division of the trigeminal ganglion.

METHODOLOGY

Stimulation of these nociceptive specific nerve fibers is painful and produces neuronal activation in the trigeminal nucleus caudalis. Preclinical models of headache have taken advantage of this primarily nociceptive pathway, and various animal models use dural trigeminovascular nociception to assay aspects of head pain. These assays measure responses at the level of the dural vasculature and the central trigeminal nucleus caudalis as a correlate of trigeminovascular activation thought to be involved in headache.

SUMMARY

This review will summarize the history of the development of models of dural trigeminovascular nociception, including intravital microscopy and laser Doppler flowmetry at the level of the vasculature, and electrophysiology and Fos techniques used to observe neuronal activation at the trigeminal nucleus caudalis. It will also describe some of pitfalls of these assays and developments for the future.

Peripheral neuromodulation and headaches: history, clinical approach, and considerations on underlying mechanisms

Implantable peripheral neurostimulation was introduced in 1969 as a potential treatment for certain neuropathic pain syndromes, primarily involving the limbs. While a few early studies included implants for occipital neuralgia, serious interest in its potential as a treatment for head pain came only after our 1999 report of positive findings in a series of patients with occipital neuralgia. Subsequent investigators confirmed these initial findings, and then extended the application to patients with various primary headache disorders, including migraine. While most found a therapeutic response, the degree of that response varied significantly, and analysis suggests that the issue of paresthesia concordancy may be central, both in explaining the data, as well as providing direction for future endeavors. Therefore, while at present peripheral neurostimulation is gaining increasing acceptance as a treatment for chronic headaches, the precise clinical indications and procedures, as well as the underlying neurophysiological mechanisms, are still being worked out.

Safety and efficacy of peripheral nerve stimulation of the occipital nerves for the management of chronic migraine: results from a randomized, multicenter, double-blinded, controlled study

BACKGROUND

Chronic migraine (CM) is a debilitating neurological disorder with few treatment options. Peripheral nerve stimulation (PNS) of the occipital nerves is a potentially promising therapy for CM patients.

METHODS

In this randomized, controlled multicenter study, patients diagnosed with CM were implanted with a neurostimulation device near the occipital nerves and randomized 2:1 to active (n = 105) or sham (n = 52) stimulation. The primary endpoint was a difference in the percentage of responders (defined as patients that achieved a ≥50% reduction in mean daily visual analog scale scores) in each group at 12 weeks.

RESULTS

There was not a significant difference in the percentage of responders in the Active compared with the Control group (95% lower confidence bound (LCB) of -0.06; p = 0.55). However, there was a significant difference in the percentage of patients that achieved a 30% reduction (p = 0.01). Importantly, compared with sham-treated patients, there were also significant differences in reduction of number of headache days (Active Group = 6.1, baseline = 22.4; Control Group = 3.0, baseline = 20.1; p = 0.008), migraine-related disability (p = 0.001) and direct reports of pain relief (p = 0.001). The most common adverse event was persistent implant site pain.

CONCLUSION

Although this study failed to meet its primary endpoint, this is the first large-scale study of PNS of the occipital nerves in CM patients that showed significant reductions in pain, headache days, and migraine-related disability. Additional controlled studies using endpoints that have recently been identified and accepted as clinically meaningful are warranted in this highly disabled patient population with a large unmet medical need.

TRIAL REGISTRATION

Clinical trials.gov (NCT00615342).

Where does a migraine attack originate? In the brainstem

Migraine is a common, paroxysmal, highly disabling primary headache disorder. The origin of migraine attacks is enigmatic. Numerous clinical and experimental results suggest that the activation of distinct brainstem nuclei is crucial in its pathogenesis, but the primary cause of this activation is not fully understood. We conclude that the initialization of a migraine attack can be explained as an altered function of the neuronal elements of the brainstem nuclei. In light of our findings and the literature data, we can assume that migraine is a subcortical disorder of a specific brainstem area.

Occipital nerve stimulation for the treatment of intractable chronic migraine headache: ONSTIM feasibility study

BACKGROUND

Medically intractable chronic migraine (CM) is a disabling illness characterized by headache ≥15 days per month.

METHODS

A multicenter, randomized, blinded, controlled feasibility study was conducted to obtain preliminary safety and efficacy data on occipital nerve stimulation (ONS) in CM. Eligible subjects received an occipital nerve block, and responders were randomized to adjustable stimulation (AS), preset stimulation (PS) or medical management (MM) groups.

RESULTS

Seventy-five of 110 subjects were assigned to a treatment group; complete diary data were available for 66. A responder was defined as a subject who achieved a 50% or greater reduction in number of headache days per month or a three-point or greater reduction in average overall pain intensity compared with baseline. Three-month responder rates were 39% for AS, 6% for PS and 0% for MM. No unanticipated adverse device events occurred. Lead migration occurred in 12 of 51 (24%) subjects.

CONCLUSION

The results of this feasibility study offer promise and should prompt further controlled studies of ONS in CM.

Migraine is a neuronal disease

Migraine is a common, paroxysmal, highly disabling primary headache disorder with a genetic background. The primary cause and the origin of migraine attacks are enigmatic. Numerous clinical and experimental results suggest that activation of the trigeminal system (TS) is crucial in its pathogenesis, but the primary cause of this activation is not fully understood. Since activation of the peripheral and central arms of the TS might be related to cortical spreading depression and to the activity of distinct brainstem nuclei (e.g. the periaqueductal grey), we conclude that migraine can be explained as an altered function of the neuronal elements of the TS, the brainstem, and the cortex, the centre of this process comprising activation of the TS. In light of our findings and the literature data, therefore, we can assume that migraine is mainly a neuronal disease.

Combined occipital and supraorbital neurostimulation for the treatment of chronic migraine headaches: Initial experience

A novel approach to the treatment of chronic migraine headaches based on neurostimulation of both occipital and supraorbital nerves was developed and reduced to clinical practice in a series of patients with headaches unresponsive to currently available therapies. Following positive trials, seven patients with chronic migraine and refractory chronic migraine headaches had permanent combined occipital nerve–supraorbital nerve neurostimulation systems implanted. The relative responses to two stimulation programs were evaluated: one that stimulated only the occipital leads and one that stimulated both the occipital and supraorbital leads together. With follow-up ranging from 1 to 35 months all patients reported a full therapeutic response but only to combined supraorbital–occipital neurostimulation. Occipital nerve stimulation alone provided a markedly inferior and inadequate response. Combined occipital nerve–supraorbital nerve neurostimulation systems may provide effective treatment for patients with chronic migraine and refractory chronic migraine headaches. For patients with chronic migraine headaches the response to combined systems appears to be substantially better than occipital nerve stimulation alone.

Migraine in the triptan era: progresses achieved, lessons learned and future developments

Triptans, serotonin 5-HT1B/1D receptor agonists, more than revolutionizing the treatment of migraine, stimulated also ground breaking research that provided insights into the anatomy, physiology, and molecular pharmacology of migraine. This knowledge, in turn, is stimulating research on new mechanisms of action for the treatment of migraine. Accordingly, it is opportune to critically review the main advances in migraine science that happened in the triptan era. Herein we first review and conceptualize some of the progresses achieved in migraine science during the triptan era. We then review the class of the triptans - mechanism of action and clinical evidence. We close by briefly discussing the class of CGRP receptor antagonists, which is currently being developed for the acute treatment of migraine.

Migraine in the triptan era: lessons from epidemiology, pathophysiology, and clinical science

The triptan era has been a time of remarkable progress for migraine diagnosis and treatment. In this paper, we review some of the advances achieved in migraine science during this era focusing on 3 themes: lessons from clinical practice, lessons from epidemiology and lessons from pathophysiology. Science has shown that migraine is a disorder of the brain, and that the key events happen in the the trigeminal neuronal pathways, not on blood vessels. Clinical science has led to the observation that migraine sometimes progresses or remits. This in turn led to longitudinal epidemiologic studies focusing on factors that determine migraine prognosis. In addition, these studies raised questions about the mechanisms of migraine progression, including the role of allodynia, obesity, inflammation, and medications as determinants of progression. This in turn opens a new set of scientific questions about the neurobiologic determinants of migraine, as well as of its clinical course, and exciting opportunities to develop new therapies for this highly disabling brain disorder.

The Role of Cervical Dysfunction in Migraine: A Systematic Review

This systematic review evaluates the strength of the evidence for the role of cervical musculoskeletal dysfunction in migraine. In this review, cervical musculoskeletal dysfunction will refer to the abnormal sensory afferentation from cervical region structures contained within the receptive field of the trigeminocervical nucleus. Electronic database searches using MEDLINE, PubMed and CINAHL were performed, and 17 studies investigating cervical musculoskeletal dysfunction in people with migraine were selected for review. The methodological quality of the included studies was assessed by two independent reviewers using a customized checklist. The review found that intersubject differences were inadequately reported and controlled, which resulted in grouping of participants with varying pathologies and symptoms. A diverse range of assessment procedures was used by the reviewed studies, which made comparison of their findings difficult. The assessment procedures were mainly used to quantify the degree of cervical musculoskeletal dysfunction, rather than to identify a cause and effect relationship between cervical structure and migrainous pain. Although animal study evidence proposes a role for cervical musculoskeletal dysfunction in migraine, this systematic review of the literature found that there is currently no convincing evidence to confirm this phenomenon in humans.

Neurostimulation in primary headache syndromes

Neurostimulation therapy involves the use of peripheral or central nerve electrical stimulation approaches for the treatment of medically intractable headache. Currently, for peripheral stimulation the main approach is that of occipital nerve stimulation, while for central stimulation deep-brain approaches with the target of the region of the posterior hypothalamic gray matter have been explored. Target conditions include migraine and the trigeminal autonomic cephalalgias: cluster headache, paroxysmal hemicrania and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing/cranial autonomic features (SUNCT/SUNA), as well as hemicrania continua. The initial results are encouraging and given the very significant disability of medically intractable primary headaches, this is a very promising area for patients and physicians alike.