Localization of 3H-dihydroergotamine-binding sites in the cat central nervous system: relevance to migraine

The influence of pharmacodynamics and pharmacokinetics on the antimigraine efficacy and safety of novel anti-CGRPergic pharmacotherapies: a narrative review

INTRODUCTION

Migraine is a complex disorder, and its etiology is not yet fully understood. In the last 40 years, calcitonin gene-related peptide (CGRP) has been central to the understanding of migraine pathophysiology, leading to the development of new molecules targeting the CGRPergic system. These new molecules, such as gepants and monoclonal antibodies, are effective, well-tolerated, and safe, and are approved for clinical use.

AREAS COVERED

By searching multiple electronic scientific databases, this narrative review examined: (i) the role of CGRP in migraine; and (ii) the current knowledge on the effects of CGRPergic antimigraine pharmacotherapies, including a brief analysis of their pharmacodynamic and pharmacokinetic characteristics.

EXPERT OPINION

Current anti-CGRPergic medications, although effective, have limitations, such as side effects and lack of antimigraine efficacy in some patients. The existence of patients with medication-resistant migraine may be due to the: (i) complex migraine pathophysiology, in which several systems appear to be deregulated before, during, and after a migraine attack; and (ii) pharmacodynamic and pharmacokinetic properties of antimigraine medications. As envisioned here, although seminal studies support the notion that CGRP plays a key role in migraine headache, the dysfunction of CGRPergic transmission does not seem to be relevant in all cases.

Dihydroergotamine mesylate nasal spray: an acute treatment option for migraine in adults

INTRODUCTION

Although the landscape of migraine symptomatic treatment has been enriched by novel effective drugs, it is mandatory to critically reappraise older molecules to ascertain whether they could still represent reliable alternatives in specific endophenotypes of patients or migraine attacks. Among these, dihydroergotamine (DHE) nasal spray has been shown to be effective and is characterized by greater tolerability and manageability than the parenteral DHE formulation.

AREAS COVERED

In this narrative review, the authors describe the pharmacodynamic and pharmacokinetic properties of DHE nasal spray and explore the results of the trials which explored its efficacy, safety and tolerability as migraine symptomatic treatment. They also discuss the limitations of the classically used device and the attempts that several companies are carrying out to generate devices warranting a more reproducible drug absorption.

EXPERT OPINION

DHE nasal spray could be considered as rescue treatment in patients who have failed other symptomatic therapeutic strategies. Nevertheless, in the perspective of tailored therapy, the intranasal route of administration and the consequent rapid onset of action may represent benefits putatively making DHE a treatment of choice for challenging migraine attacks such as those with nocturnal onset or quickly reaching the climax of both headache and neurovegetative associated symptoms.

Migraine: from pathophysiology to treatment

Migraine is an extremely disabling, common neurological disorder characterized by a complex neurobiology, involving a series of central and peripheral nervous system areas and networks. A growing increase in the understanding of migraine pathophysiology in recent years has facilitated translation of that knowledge into novel treatments, which are currently becoming available to patients in many parts of the world and are substantially changing the clinical approach to the disease. In the first part of this review, we will provide an up to date overview of migraine pathophysiology by analyzing the anatomy and function of the main regions involved in the disease, focusing on how these give rise to the plethora of symptoms characterizing the attacks and overall disease. The second part of the paper will discuss the novel therapeutic agents that have emerged for the treatment of migraine, including molecules targeting calcitonin gene-related peptide (gepants and monoclonal antibodies), serotonin 5-HT_1F receptor agonists (ditans) and non-invasive neuromodulation, as well as providing a brief overview of new evidence for classic migraine treatments.

Migraine Frequency Decrease Following Prolonged Medical Cannabis Treatment: A Cross-Sectional Study

Background: Medical cannabis (MC) treatment for migraine is practically emerging, although sufficient clinical data are not available for this indication. This cross-sectional questionnaire-based study aimed to investigate the associations between phytocannabinoid treatment and migraine frequency. Methods: Participants were migraine patients licensed for MC treatment. Data included self-reported questionnaires and MC treatment features. Patients were retrospectively classified as responders vs. non-responders (≥50% vs. <50% decrease in monthly migraine attacks frequency following MC treatment initiation, respectively). Comparative statistics evaluated differences between these two subgroups. Results: A total of 145 patients (97 females, 67%) with a median MC treatment duration of three years were analyzed. Compared to non-responders, responders (n = 89, 61%) reported lower current migraine disability and lower negative impact, and lower rates of opioid and triptan consumption. Subgroup analysis demonstrated that responders consumed higher doses of the phytocannabinoid ms_373_15c and lower doses of the phytocannabinoid ms_331_18d (3.40 95% CI (1.10 to 12.00); p < 0.01 and 0.22 95% CI (0.05–0.72); p < 0.05, respectively). Conclusions: These findings indicate that MC results in long-term reduction of migraine frequency in >60% of treated patients and is associated with less disability and lower antimigraine medication intake. They also point to the MC composition, which may be potentially efficacious in migraine patients.

Recent Advances in Pharmacotherapy for Migraine Prevention: From Pathophysiology to New Drugs

Migraine is a common and disabling neurological disorder, with a significant socioeconomic burden. Its pathophysiology involves abnormalities in complex neuronal networks, interacting at different levels of the central and peripheral nervous system, resulting in the constellation of symptoms characteristic of a migraine attack. Management of migraine is individualised and often necessitates the commencement of preventive medication. Recent advancements in the understanding of the neurobiology of migraine have begun to account for some parts of the symptomatology, which has led to the development of novel target-based therapies that may revolutionise how migraine is treated in the future. This review will explore recent advances in the understanding of migraine pathophysiology, and pharmacotherapeutic developments for migraine prevention, with particular emphasis on novel treatments targeted at the calcitonin gene-related peptide (CGRP) pathway.

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.

An update on migraine: current understanding and future directions

Migraine is a common brain disorder with high disability rates which involves a series of abnormal neuronal networks, interacting at different levels of the central and peripheral nervous system. An increase in the interest around migraine pathophysiology has allowed researchers to unravel certain neurophysiological mechanisms and neurotransmitter involvement culminating in the recent development of novel therapies, which might substantially change the clinical approach to migraine patients. The present review will highlight the current aspects of migraine pathophysiology, covering an understanding of the complex workings of the migraine state and the brain regions responsible for them. We will further discuss the therapeutic agents which have appeared in the most recent years for migraine care, from calcitonin gene-related peptide (CGRP) receptor antagonists, gepants; through serotonin 5-HT1F receptor agonists, ditans, and CGRP or CGRP receptor monoclonal antibodies to invasive and non-invasive neuromodulation techniques.

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.

Ictal lack of binding to brain parenchyma suggests integrity of the blood-brain barrier for 11C-dihydroergotamine during glyceryl trinitrate-induced migraine

See Dreier (doi: 10.1093/aww112 ) for a scientific commentary on this article.

For many decades a breakdown of the blood–brain barrier has been postulated to occur in migraine. Hypothetically this would facilitate access of medications, such as dihydroergotamine or triptans, to the brain despite physical properties otherwise restricting their entry. We studied the permeability of the blood–brain barrier in six migraineurs and six control subjects at rest and during acute glyceryl trinitrate-induced migraine attacks using positron emission tomography with the novel radioligand ¹¹ C-dihydroergotamine, which is chemically identical to pharmacologically active dihydroergotamine. The influx rate constant K _i , average dynamic image and time activity curve were assessed using arterial blood sampling and served as measures for receptor binding and thus blood–brain barrier penetration. At rest, there was binding of ¹¹ C-dihydroergotamine in the choroid plexus, pituitary gland, and venous sinuses as expected from the pharmacology of dihydroergotamine. However, there was no binding to the brain parenchyma, including the hippocampus, the area with the highest density of the highest-affinity dihydroergotamine receptors, and the raphe nuclei, a postulated brainstem site of action during migraine, suggesting that dihydroergotamine is not able to cross the blood–brain barrier. This binding pattern was identical in migraineurs during glyceryl trinitrate-induced migraine attacks as well as in matched control subjects. We conclude that ¹¹ C-dihydroergotamine is unable to cross the blood–brain barrier interictally or ictally demonstrating that the blood–brain barrier remains tight for dihydroergotamine during acute glyceryl trinitrate-induced migraine attacks.

Comprehensive Review of Medicinal Marijuana, Cannabinoids, and Therapeutic Implications in Medicine and Headache: What a Long Strange Trip It's Been …

BACKGROUND

The use of cannabis, or marijuana, for medicinal purposes is deeply rooted though history, dating back to ancient times. It once held a prominent position in the history of medicine, recommended by many eminent physicians for numerous diseases, particularly headache and migraine. Through the decades, this plant has taken a fascinating journey from a legal and frequently prescribed status to illegal, driven by political and social factors rather than by science. However, with an abundance of growing support for its multitude of medicinal uses, the misguided stigma of cannabis is fading, and there has been a dramatic push for legalizing medicinal cannabis and research. Almost half of the United States has now legalized medicinal cannabis, several states have legalized recreational use, and others have legalized cannabidiol-only use, which is one of many therapeutic cannabinoids extracted from cannabis. Physicians need to be educated on the history, pharmacology, clinical indications, and proper clinical use of cannabis, as patients will inevitably inquire about it for many diseases, including chronic pain and headache disorders for which there is some intriguing supportive evidence.

OBJECTIVE

To review the history of medicinal cannabis use, discuss the pharmacology and physiology of the endocannabinoid system and cannabis-derived cannabinoids, perform a comprehensive literature review of the clinical uses of medicinal cannabis and cannabinoids with a focus on migraine and other headache disorders, and outline general clinical practice guidelines.

CONCLUSION

The literature suggests that the medicinal use of cannabis may have a therapeutic role for a multitude of diseases, particularly chronic pain disorders including headache. Supporting literature suggests a role for medicinal cannabis and cannabinoids in several types of headache disorders including migraine and cluster headache, although it is primarily limited to case based, anecdotal, or laboratory-based scientific research. Cannabis contains an extensive number of pharmacological and biochemical compounds, of which only a minority are understood, so many potential therapeutic uses likely remain undiscovered. Cannabinoids appear to modulate and interact at many pathways inherent to migraine, triptan mechanisms ofaction, and opiate pathways, suggesting potential synergistic or similar benefits. Modulation of the endocannabinoid system through agonism or antagonism of its receptors, targeting its metabolic pathways, or combining cannabinoids with other analgesics for synergistic effects, may provide the foundation for many new classes of medications. Despite the limited evidence and research suggesting a role for cannabis and cannabinoids in some headache disorders, randomized clinical trials are lacking and necessary for confirmation and further evaluation.

Intravenous dexamethasone to prevent the recurrence of benign headache after discharge from the emergency department: a randomized, double-blind, placebo-controlled clinical trial

Objective:

To evaluate whether the addition of intravenous (IV) dexamethasone to standard emergency department (ED) benign headache therapy would reduce the incidence of headache recurrence at 48–72 hours.

Methods:

This randomized, double-blind, placebo-controlled clinical trial of adult patients presenting with the chief complaint of headache was conducted in the ED of 2 academic, urban Level 1 hospitals. Headache evaluation and therapy were determined by the treating physician, and, before discharge, patients were administered either 10 mg of IV dexamethasone or placebo. The treatment groups had similar baseline characteristics, abortive therapy, IV fluids and degree of pain relief achieved before discharge. Patients were contacted 48–72 hours following discharge and asked whether their headache was “better,” “worse” or “remained unchanged” when compared with their symptoms at discharge. Those whose headaches were “worse” or “unchanged,” and those who reported a return of headache after being pain free at discharge were considered to be treatment failures and classified as having had a recurrence. The patient's headache at follow-up was further categorized as severe (i.e., provoking another physician visit or interfering with daily activity) or mild (i.e., requiring self-medication or no treatment).

Results:

Fifty-seven patients met the inclusion criteria and 2 were lost to follow-up, leaving 55 for analysis. At follow-up, 9.7% (3/31) of those receiving dexamethasone had headache recurrence, versus 58.3% (14/24) of those receiving placebo (p&lt; 0.001). Four dexamethasone recipients (12.9%) had severe headaches at follow-up compared with 8 (33.3%) in the placebo group (p= 0.14).

Conclusions:

In this study, IV dexamethasone reduced headache recurrence at 48–72-hour follow-up. Given its excellent safety profile and likely benefit, IV dexamethasone should be considered for ED headache patients after standard evaluation and therapy.

Dexamethasone prevents relapse after emergency department treatment of acute migraine: a randomized clinical trial

Objective:

To determine whether the addition of intravenous dexamethasone to standard emergency department (ED) migraine therapy would decrease the incidence of severe recurrent headache 24 to 48 hours after initial treatment.

Methods:

Patients aged 19 to 65 years whose headache was severe enough to require parenteral therapy and who met International Headache Society migraine criteria were eligible for this randomized, double-blind trial. The study was conducted in the ED of 2 community hospitals, 1 of which was a tertiary referral centre. Exclusion criteria included pregnancy, focal findings, fever, meningismus, allergy to the study drug, active peptic ulcer disease and diabetes mellitus. Demographic and clinical data, including headache severity, were recorded. After abortive therapy (antiemetics, intravenous nonsteroidal agents, dihydroergotamine or opioids), blinded nurses administered dexamethasone (24 mg intravenously) or placebo. Patients recorded headache severity on a Visual Analogue Scale (VAS) at time T = 0, T = 30 minutes and T = 60 minutes and at discharge. They were contacted 48 to 72 hours later and asked whether they had suffered a recurrence of their headache, categorized as class A (severe, provoking another physician visit), class B (severe, interfering with daily activity but not provoking a physician visit), class C (mild, requiring self-medication but not limiting activity) or class D (mild, requiring no treatment). Results: Two of 100 patients were lost to follow-up, leaving 98 in the study sample. Placebo recipients were more likely to be female; other baseline characteristics were similar between groups. Median VAS pain score was 83 mm on ED arrival, 35 mm after initial treatment and 12 mm on discharge. At follow-up, 65 of 98 patients had suffered headache recurrence. In the placebo versus dexamethasone groups, respectively, the results were 11 versus 0 in class A, 11 versus 9 in class B, 7 versus 11 in class C and 4 versus 12 in class D. Regarding the primary outcome, 9 of 49 dexamethasone patients (18%) and 22 of 49 placebo patients (45%) had severe (classes A and B) recurrent headache (odds ratio 0.28; 95% CI, 0.11 to 0.69;p= 0 .005).

Conclusions:

Migraine recurrence is common after “successful” ED treatment. Inflammation may be a critical factor in migraine genesis. Intravenous dexamethasone decreases the incidence of severe recurrent headache after ED treatment and should be offered to patients thought to be at risk of recurrent headache.

Exacerbation of SUNCT and SUNA syndromes during intravenous dihydroergotamine treatment: A case series

BACKGROUND

The management of short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) and with short-lasting unilateral neuralgiform headache attacks with autonomic symptoms (SUNA) remains challenging in view of the limited understanding of their pathophysiological mechanisms.

METHODS

An initial observation that patients with both chronic migraine (CM) or cluster headache (CH) and SUNCT/SUNA receiving intravenous dihydroergotamine (IV DHE) had complained of dramatic worsening of the latter led to review of the case notes of patients with CM or CH and co-existent SUNCT/SUNA seen between 2008 and 2013 and who had a trial of IV DHE.

RESULTS

Twenty-four patients were identified. IV DHE was ineffective for SUNCT/SUNA in 16 patients, while one patient reported a marginal improvement. Five patients reported dramatic worsening of the SUNCT/SUNA. Moreover, two patients developed new-onset SUNA during their first IV DHE infusion. Out of these seven patients, those requiring repeated courses of IV DHE consistently experienced exacerbations of SUNCT/SUNA which were suppressed with IV lidocaine.

CONCLUSIONS

DHE is an ineffective treatment option for SUNCT and SUNA. Physicians who intend to offer IV DHE to CH or CM patients should warn them that IV DHE could exacerbate and possibly even lead to a de novo onset of SUNCT/SUNA. In view of the reported worsening or new onset of SUNCT/SUNA in patients using dopamine agonists for the treatment of pituitary prolactinomas, we speculate that DHE might worsen or induce SUNCT and SUNA, at least in a sub-group of patients, through a perturbation in the dopaminergic system.

Functional neuroimaging of primary headache disorders

Until recently, primary headache disorders, such as migraine and cluster headache were considered to be vascular in origin. However, advances in neuroimaging techniques, such as positron emission tomography, single photon emission computed tomography and functional magnetic resonance imaging have augmented the growing clinical evidence that these headaches are primarily driven from the brain. This review covers functional imaging studies in migraine, cluster headache, rarer headache syndromes and experimental head pain. Together with newer techniques, such as voxel-based morphometry and magnetic resonance spectrometry, functional imaging continues to play a role in elucidating and targeting the neural substrates in each of the primary headache syndromes.

Migraine in gulf war illness and chronic fatigue syndrome: prevalence, potential mechanisms, and evaluation

Objective: To assess the prevalence of headache subtypes in Gulf War Illness (GWI) and Chronic Fatigue Syndrome (CFS) compared to controls.

Background: Approximately, 25% of the military personnel who served in the 1990–1991 Persian Gulf War have developed GWI. Symptoms of GWI and CFS have considerable overlap, including headache complaints. Migraines are reported in CFS. The type and prevalence of headaches in GWI have not been adequately assessed.

Methods: 50 GWI, 39 CFS and 45 controls had structured headache evaluations based on the 2004 International Headache Society criteria. All subjects had history and physical examinations, fatigue and symptom related questionnaires, measurements of systemic hyperalgesia (dolorimetry), and assessments for exclusionary conditions.

Results: Migraines were detected in 64% of GWI (odds ratio = 11.6 [4.1–32.5]) (mean [±95% CI]) and 82% of CFS subjects (odds ratio = 22.5 [7.8–64.8]) compared to only 13% of controls. There was a predominance of females in the CFS compared to GWI and controls. However, migraine status was independent of gender in GWI and CFS groups (x² = 2.7; P = 0.101). Measures of fatigue, pain, and other ancillary criteria were comparable between GWI and CFS subjects with and without headache.

Conclusion: The high prevalence of migraine in CFS was confirmed and extended to GWI subjects. GWI and CFS may share dysfunctional central pathophysiological pathways that contribute to migraine and subjective symptoms. The high migraine prevalence warrants the inclusion of a structured headache evaluation in GWI and CFS subjects, and treatment when present.

Pathophysiology of migraine

Migraine is a common disabling brain disorder whose pathophysiology is now being better understood. The study of anatomy and physiology of pain producing structures in the cranium and the central nervous system modulation of the input have led to the conclusion that migraine involves alterations in the sub-cortical aminergic sensory modulatory systems that influence the brain widely.

Beyond neurovascular: migraine as a dysfunctional neurolimbic pain network

No single model of migraine explains all of the known features of the disorder. Migraine has recently been characterized as an abnormality in pain-modulating circuits in the brainstem. The periaqueductal gray appears to have a critical role in migraine genesis and has been labeled the "migraine generator." The concept of a "pain matrix," rather than a specific locus of pain, is widely accepted in the pain literature and offers a new dimension to understanding migraine. Recent neuroimaging studies of migraineurs suggest altered functional connectivity between brainstem pain-modulating circuits and cortical (limbic) centers. Numerous clinical observations suggest that limbic influences play an important role in migraine expression. We propose a model of migraine as a dysfunction of a "neurolimbic" pain network. The influence between brainstem and cortical centers is bidirectional, reflecting the bidirectional interaction of pain and mood. Neurolimbic dysfunction may increase as migraine becomes more chronic or refractory. The neurolimbic model expands the model of migraine as a dysfunction of brainstem nuclei. A neurolimbic model may help bridge a gap in understanding the migraine attack, the interictal dysfunctions of episodic migraine, the progression to chronic migraine, and the common comorbidities with other disorders (such as fibromyalgia, irritable bowel syndrome, and mood and anxiety disorders), which may also be considered neurolimbic. A neurolimbic model of migraine may be a useful heuristic that would impact both clinical treatment and research agendas, as well as education of physicians and patients.

MAP0004, orally inhaled dihydroergotamine for acute treatment of migraine: efficacy of early and late treatments

OBJECTIVE

To evaluate the efficacy of MAP0004, an orally inhaled dihydroergotamine, for acute treatment of migraine when administered at various time points from within 1 hour to more than 8 hours after migraine onset.

PATIENTS AND METHODS

This post hoc subanalysis was conducted using data from 902 patients enrolled in a randomized, double-blind, placebo-controlled, 2-arm, phase 3, multicenter study conducted from July 14, 2008, through March 23, 2009. End points were 2-hour pain relief and pain-free rates in patients who treated a migraine in ≤1 hour, from >1 hour to ≤4 hours, from >4 to ≤8 hours, or in >8 hours after onset of migraine, given that patients may be unwilling or unable to initiate treatment at headache inception.

RESULTS

Treatment with MAP0004 was significantly more effective than placebo in relieving pain at all treatment points (≤1 hour after start of migraine: 66% [74/112] for MAP0004 vs 41% [48/118] for placebo, P<.001; >1 to ≤4 hours: 60% [91/153] vs 35% [58/168], P<.001; >4 to ≤8 hours: 53% [36/68] vs 30% [16/54], P=.008; and >8 hours: 48% [25/52] vs 24% [11/46], P=.007). Pain-free rates were also significantly higher with MAP0004 than placebo for treatment within 8 hours after migraine onset (≤1 hour: 38% [43/112] for MAP0004 vs 13% [15/118] for placebo, P<.001; >1 to ≤4 hours: 28% [43/153] vs 10% [17/168], P<.001; >4 to ≤8 hours: 22% [15/68] vs 7% [4/54], P<.025) but not at >8 hours (19% [10/52] vs 9% [4/46], P=.106).

CONCLUSION

This post hoc subanalysis shows that MAP0004 was effective in treating migraine irrespective of the time of treatment, even more than 8 hours after onset of migraine pain.

Acute migraine therapy: new drugs and new approaches

OPINION STATEMENT

The conceptual shift of our understanding of migraine from a vascular disorder to a brain disorder has dramatically altered the approach to the development of new medicines in the field. Current pharmacologic treatments of acute migraine consist of nonspecific and relatively specific agents. Migraine-specific drugs comprise two classes, the ergot alkaloid derivatives and the triptans, serotonin 5-HT(1B/1D) receptor agonists. The ergots, consisting of ergotamine and dihydroergotamine (DHE), are the oldest specific antimigraine drugs available and are considered relatively safe and effective. Ergotamine has been used less extensively because of its adverse effects; DHE is better tolerated. The triptan era, beginning in the 1990s, was a period of considerable change, although these medicines retained vasoconstrictor actions. New methods of delivering older drugs include orally inhaled DHE and the transdermal formulation of sumatriptan, both currently under study. Novel medicines being developed are targeted at neural sites of action. Serotonin 5-HT(1F) receptor agonists have proven effective in phase II studies and have no vascular actions. Calcitonin gene-related peptide (CGRP) receptor antagonists are another promising nonvasoconstrictor approach to treating acute migraine. Olcegepant (BIBN4096BS) and telcagepant (MK-0974) have been shown to be safe and effective in phase I, II, and (for telcagepant) phase III clinical trials. Other targets under investigation include glutamate (AMPA/kainate), TRPV1, prostanoid EP4, and nitric oxide synthase. With new neural targets and the potential for therapeutic advances, the next era of antimigraine medications is near.

A trans-cultural comparison of the organisation of care at headache centres world-wide

Background: The need to provide better outcomes for patients with headache, and to minimise the costs involved in doing so, has prompted the search for new modes of service delivery by exploring the service organisation and nursing role from various cultural, economic and global perspectives.

Materials and Methods: This study was based on comparisons with the UK headache service up to 2007, the point at which this study was set up. This UK service was based at the National Hospital for Neurology and Neurosurgery (NHNN, UCLH Trust). Data were obtained from US headache centres in 2008 and from centres in Copenhagen, Bangkok, Sydney and Porto Alegre in 2009.

Results: A comparison shows the key components of services at all centres showing the team structure and size of service. Prominent features at the centres included: team-working, regular meetings, educational input, good access and communication among team members, headache-trained neurologists, specialist nursing at most centres, and the input of psychological and physical therapists at some centres.

Conclusions: The problems of tertiary headache care are very similar throughout the world and seem to transcend ethnic, cultural and economic considerations.

Migraine, allodynia, and implications for treatment

Allodynia--perception of pain from non-noxious stimuli--is a common clinical feature in various pain syndromes. The significance for migraine has increasingly been recognized and the pathophysiology has been investigated in detail. Allodynia is a marker for sensitization of central trigeminal neurons. Intensity and persistence of allodynic symptoms are a function of duration of migraine attacks, frequency of attacks, and migraine history. It has been hypothesized that treatment success with triptans may be severely impaired in the presence of allodynia. However, randomized controlled trials did not confirm that. Treatment with cyclooxygenase inhibitors and dihydroergotamine does not seem to be limited by allodynia; these medications may be able to reverse allodynia. Data on the new class of calcitonin-gene related-peptide antagonists are not yet available. Additional and more refined randomized controlled trials, focusing on methodological issues pertaining to the determination of allodynia, are warranted to resolve the true relationship between allodynia and treatment response. Regardless--based on available randomized controlled trials--the recommendation prevails to initiate abortive treatment as soon as possible after attack onset when pain is still mild.

Investigation of gamma-aminobutyric acid (GABA) A receptors genes and migraine susceptibility

BACKGROUND

Migraine is a neurological disorder characterized by recurrent attacks of severe headache, affecting around 12% of Caucasian populations. It is well known that migraine has a strong genetic component, although the number and type of genes involved is still unclear. Prior linkage studies have reported mapping of a migraine gene to chromosome Xq 24-28, a region containing a cluster of genes for GABA A receptors (GABRE, GABRA3, GABRQ), which are potential candidate genes for migraine. The GABA neurotransmitter has been implicated in migraine pathophysiology previously; however its exact role has not yet been established, although GABA receptors agonists have been the target of therapeutic developments. The aim of the present research is to investigate the role of the potential candidate genes reported on chromosome Xq 24-28 region in migraine susceptibility. In this study, we have focused on the subunit GABA A receptors type epsilon (GABRE) and type theta (GABRQ) genes and their involvement in migraine.

METHODS

We have performed an association analysis in a large population of case-controls (275 unrelated Caucasian migraineurs versus 275 controls) examining a set of 3 single nucleotide polymorphisms (SNPs) in the coding region (exons 3, 5 and 9) of the GABRE gene and also the I478F coding variant of the GABRQ gene.

RESULTS

Our study did not show any association between the examined SNPs in our test population (P>0.05).

CONCLUSION

Although these particular GABA receptor genes did not show positive association, further studies are necessary to consider the role of other GABA receptor genes in migraine susceptibility.

The blood-brain barrier in migraine treatment

Salient aspects of the anatomy and function of the blood-barrier barrier (BBB) are reviewed in relation to migraine pathophysiology and treatment. The main function of the BBB is to limit the access of circulating substances to the neuropile. Smaller lipophilic substances have some access to the central nervous system by diffusion, whereas other substances can cross the BBB by carrier-mediated influx transport, receptor-mediated transcytosis and absorptive-mediated transcytosis. Studies of drugs relevant to migraine pathophysiology and treatment have been examined with the pressurized arteriography method. The drugs, given both luminally and abluminally, provide important notions regarding antimigraine site of action, probably abluminal to the BBB. The problems with the BBB in animal models designed to study the pathophysiology, acute treatment models and preventive treatments are discussed with special emphasize on the triptans and calcitonin gene-related peptide (CGRP). The human experimental headache model, especially the use of glycerol trinitrate (the nitric oxide model), and experiences with CGRP administrations utilize the systemic administration of the agonists with effects on other vascular beds also. We discuss how this can be related to genuine migraine attacks. Our view is that there exists no clear proof of breakdown or leakage of the BBB during migraine attacks, and that antimigraine drugs need to pass the BBB for efficacy.

DHE in the pharmacotherapy of migraine: potential for a larger role

Despite a large array of currently marketed, frequently effective drugs for the acute treatment of migraine headache, comprising various classes and formulations, predictably reliable treatment for most headache types is often lacking. Dihydroergotamine mesylate (DHE) is a comparatively safe and effective therapy for migraine headache that could potentially be used for a broader range of headache types than occurs at present. The features of DHE supporting this assertion include (1) effectiveness in terminating severe, long-lasting headaches, (2) rapid onset of action, (3) very low rates of headache recurrence, (4) minimal risk of medication-overuse headache, and (5) in the nasal spray formulation, suitability for outpatients (especially patients who are very nauseated or vomiting, potentially obviating the need for an office or hospital visit for acute care). Conditions or circumstances for which there are data supporting the expanded use of DHE include menstrual migraine, migraine with central sensitization and cutaneous allodynia, medication-overuse headache, migraine recurrence, and status migrainosus. The introduction of the intranasal formulation of DHE provides both pharmacologic and patient-convenience advantages for use in migraine therapy. This article reviews the rationale for the use of DHE in these common, often difficult-to-treat migraine forms.

A review of diagnostic and functional imaging in headache

The neuroimaging of headache patients has revolutionised our understanding of the pathophysiology of primary headaches and provided unique insights into these syndromes. Modern imaging studies point, together with the clinical picture, towards a central triggering cause. The early functional imaging work using positron emission tomography shed light on the genesis of some syndromes, and has recently been refined, implying that the observed activation in migraine (brainstem) and in several trigeminal-autonomic headaches (hypothalamic grey) is involved in the pain process in either a permissive or triggering manner rather than simply as a response to first-division nociception per se. Using the advanced method of voxel-based morphometry, it has been suggested that there is a correlation between the brain area activated specifically in acute cluster headache--the posterior hypothalamic grey matter--and an increase in grey matter in the same region. No structural changes have been found for migraine and medication overuse headache, whereas patients with chronic tension-type headache demonstrated a significant grey matter decrease in regions known to be involved in pain processing. Modern neuroimaging thus clearly suggests that most primary headache syndromes are predominantly driven from the brain, activating the trigeminovascular reflex and needing therapeutics that act on both sides: centrally and peripherally.

New insights into brain dysfunction in migraine

Headache is one of the most common presenting symptoms to a physician's office. The majority of headaches are in the category known as primary headaches, where there are no structural disturbances. Secondary headaches are uncommon and usually occur in less than 10% of patients. The mechanisms of secondary headaches are usually due to the underlying pathology. These are usually evident on neuroimaging or laboratory testing. This review will focus mainly on mechanisms of primary headache (i.e., migraine and cluster).

Responses of neurons in the spinal nucleus of the trigeminal nerve to electrical stimulation of the dura mater of the rat brain

The pathogenesis of migraine is based on the aseptic inflammation of dura mater tissues surrounding the large cranial vessels, such as the superior sagittal sinus. This inflammation develops in conditions of antidromic activation of sensory terminals of the trigeminal nerve and is accompanied by changes in the responses of neurons in the spinal nucleus of the trigeminal nerve to electrical stimulation of the superior sagittal sinus. However, the characteristics of the responses of these neurons to this stimulation have received virtually no study. Experiments on anesthetized rats were performed with recording of the responses of 387 neurons in the spinal nucleus of the trigeminal nerve to electrical stimulation of the superior sagittal sinus. The results showed that the responses of neurons to this stimulation was biphasic, consisting of a short initial phase with a latent period of 7-19 (11.4 +/- 0.17) msec, followed by a longer-lived discharge with a latent period of 20-50 (34.2 +/- 0.8) msec. It is suggested that the first phase reflects orthodromic activation of perivascular A(delta) and C fibers of the trigeminal nerve, while the second phase is associated with activation of meningeal C fibers with low conduction velocities and/or secondary activation of the perivascular sensory endings of the trigeminal nerve by algogenic and vasoactive substances released from them during antidromic activation. These changes seen in animal experiments may serve as an indicator of the efficacy of antimigraine agents.

Functional neuroimaging of primary headache disorders

Until recently, primary headache disorders such as migraine and cluster headache were considered to be vascular in origin. However, advances in neuroimaging techniques, such as positron emission tomography, single photon emission computerized tomography, and functional magnetic resonance imaging, have augmented the growing clinical evidence that these headaches are primarily driven from the brain. This review covers functional imaging studies in migraine, cluster headache, rarer headache syndromes, and experimental head pain. Together with newer techniques, such as voxel-based morphometry and magnetic resonance spectrometry, functional imaging continues to play a role in elucidating and targeting the neural substrates in each of the primary headache syndromes.

Preclinical neuropharmacology of naratriptan

The basic CNS neuropharmacology of naratriptan is reviewed here. Naratriptan is a second-generation triptan antimigraine drug, developed at a time when CNS activity was thought not to be relevant to its therapeutic effect in migraine. It was, however, developed to be a more lipid-soluble, more readily absorbed and less readily metabolized variant on preexisting triptans and these variations conferred on it a higher CNS profile. Naratriptan is a 5-HT(1B/1D) receptor agonist with a highly selective action on migraine pain and nausea, without significant effect on other pain or even other trigeminal pain. Probable sites of therapeutic action of naratriptan include any or all of: the cranial vasculature; the peripheral terminations of trigeminovascular sensory nerves; the first-order synapses of the trigeminovascular sensory system; the descending pain control system; and the nuclei of the thalamus. Naratriptan may prevent painful dilatation of intracranial vessels or reverse such painful dilatation. Naratriptan can prevent the release of sensory peptides and inhibit painful neurogenic vasodilatation of intracranial blood vessels. At the first order synapse of the trigeminal sensory system, naratriptan can selectively suppress neurotransmission from sensory fibers from dural and vascular tissue, while sparing transmission from other trigeminal fibers, probably through inhibition of neuropeptide transmitter release. In the periaqueductal gray matter and in the nucleus raphe magnus, naratriptan selectively activates inhibitory neurons which project to the trigeminal nucleus and spinal cord and which exert inhibitory influences on trigeminovascular sensory input. Naratriptan has also a therapeutic effect on the nausea of migraine, possibly exerting its action at the level of the nucleus tractus solitarius via the same mechanisms by which it inhibits trigeminovascular nociceptive input. The incidence of naratriptan-induced adverse effects in the CNS is low and it is not an analgesic for pain other than that of vascular headache. In patients receiving selective serotonin uptake inhibitors (SSRIs) naratriptan may cause serotonin syndrome-like behavioral side effects. The mechanism of action involved in the production of behavioral and other CNS side effects of naratriptan is unknown.

[The trigeminovascular system in the human. Cerebral blood flow, functional imaging and primary headache]

Primary headache syndromes, such as cluster and migraine, are widely described as vascular headaches, even though there is considerable clinical evidence to suggest that both conditions are primarily central, that is regulated by the brain. The shared anatomical and physiological substrate for both clinical syndromes is the neural innervation of the cranial circulation. Early functional imaging using PET has shed light on the genesis of both syndromes, documenting activation in the midbrain and pons in migraine and in the hypothalamic gray in cluster headache. These areas are involved in the pain process in a permissive or triggering manner rather than simply as a response to first-division nociceptive pain impulses. This article reviews findings in the physiology of the trigeminovascular system which demand renewed consideration of the neural influences in many primary headaches and the physiology of the neural innervation of cranial circulation. Primary headaches should thus be regarded as neurovascular headaches to emphasize the interaction between nerves and vessels which is their underlying characteristic.

Functional neuroimaging of primary headache disorders

Until recently, primary headache disorders such as migraine and cluster headache were considered to be vascular in origin. However, advances in neuroimaging techniques, such as positron emission tomography, single photon emission computerized tomography, and functional magnetic resonance imaging, have augmented the growing clinical evidence that these headaches are primarily driven from the brain. This review covers functional imaging studies in migraine, cluster headache, rarer headache syndromes, and experimental head pain. Together with newer techniques, such as voxel-based morphometry and magnetic resonance spectrometry, functional imaging continues to play a role in elucidating and targeting the neural substrates in each of the primary headache syndromes.

The 5-hydroxytryptamine1B/1D/1F receptor agonists eletriptan and naratriptan inhibit trigeminovascular input to the nucleus tractus solitarius in the cat

Migraine pain arises in the trigeminovascular system and is often associated with nausea and sometimes with vomiting. In this study, an in vivo cat model of trigeminovascular stimulation was used to determine first whether there is a functional connection between the trigeminovascular system and the nucleus tractus solitarius (NTS), which is involved in regulating vomiting, and second whether anti-migraine drugs have any effect on such a connection. Chloralose-anaesthetised cats (n=16) were prepared for single neuron recording. The superior sagittal sinus (SSS) was isolated and stimulated electrically. The brainstem near the obex was exposed and a metal microelectrode equipped with six glass barrels for microiontophoresis was placed in the NTS. Recordings were made from 44 NTS neurons which responded to SSS stimulation with A-delta latencies. Iontophoretic ejection (50 nA) of eletriptan or naratriptan suppressed the response in 75% (15/20) and 78% (11/14) of cells and caused an average suppression of cell firing of 42+/-5% (n=20) and 54+/-8% (n=14), respectively. This suppression could be antagonized by the concurrent ejection (20-50 nA) of the 5-HT(1B/1D) receptor antagonist GR127935. We conclude that activation of the trigeminovascular system excites cells in the NTS that can be inhibited by eletriptan and naratriptan through activation of 5-HT(1B/1D) receptors. It is possible that in patients having a migraine attack trigeminovascular activation triggers nausea and vomiting, and that the alleviation of these symptoms by anti-migraine compounds may be via an action at 5-HT(1B/1D) receptors in the NTS.

Migraine

Migraine is a very common neurobiological headache disorder that is caused by increased excitability of the CNS. It ranks among the world's most disabling medical illnesses. Diagnosis is based on the headache's characteristics and associated symptoms. The economic and societal effect of migraine is substantial: it affects patients' quality of life and impairs work, social activities, and family life. There are many acute and preventive migraine treatments. Acute treatment is either specific (triptans and ergots) or non-specific (analgesics). Disabling migraine should be treated with triptans. Increased headache frequency is an indication for preventive treatment. Preventive treatment decreases migraine frequency and improves quality of life. More treatments are being developed, which provides hope to the many patients whose migraines remain uncontrolled.

Activation of 5-HT1B/1D receptor in the periaqueductal gray inhibits nociception

It is considered that the site of action of the abortive antimigraine compounds acting at serotonin, 5-HT(1B/1D,) receptors (triptans) is the trigeminovascular system. We tested whether there is a non-trigeminal site of action. The 5-HT(1B/1D) agonist, naratriptan, was microinjected into the ventrolateral periaqueductal gray (vlPAG), and activity in the trigeminal nucleus caudalis (TNC) was monitored. Recordings were made from 20 nociceptive neurons in the dorsal horn of the TNC that received convergent input from the dura mater and face. Responses of neurons to dural, facial cutaneous and corneal stimulation were studied before and after injection of naratriptan. Naratriptan decreased the excitability to electrical stimulation of the dura mater as the A-fiber response decreased by 24 +/- 4.1% (p < 0.001) and the C-fiber response decreased by 42 +/- 8.2% (p < 0.001). Spontaneous activity was decreased by 38 +/- 7.5% (p < 0.001). After injection, the mechanical thresholds of the dura mater increased from (n = 14, p < 0.01). Responses to stimulation of the face and cornea were not altered by injection of naratriptan. These results suggest that 5-HT(1B/1D) receptor activation in the vlPAG activates descending pain-modulating pathways that inhibit dural, but not facial and corneal nociceptive input. These findings have implications for the understanding of the action of triptans in migraine and cluster headache, suggesting that brain loci other than the trigeminal nucleus may play a role in the clinical action of triptans.

Convulsive ergotism: epidemics of the serotonin syndrome?

Between 1085 and 1927, epidemics of "convulsive ergotism" were widespread east of the Rhine in Europe due to consumption of grain contaminated with ergot, which is produced by the fungus Claviceps purpurea. West of the Rhine, consumption of ergot-contaminated food caused epidemics of gangrenous ergotism. The clinical features of convulsive ergotism--muscle twitching and spasms, changes in mental state, hallucinations, sweating, and fever lasting for several weeks--suggest serotonergic overstimulation of the CNS (ie, the serotonin syndrome). The ergot alkaloids are serotonin agonists. Dihydroergotamine binds to serotonin receptors in the dorsal horn of the spinal cord, which is the site of neuropathological changes in convulsive ergotism. Dihydroergotamine given to human beings can cause the serotonin syndrome. Ergots produced by different strains of Claviceps purpurea, and those growing in different soils, may have different ergot alkaloid compositions. An alkaloid, present in high concentrations in ergots from east of the Rhine, may have caused convulsive ergotism at a circulating concentration insufficient to produce peripheral ischaemia. The serotonin syndrome may, therefore, have been a public-health problem long before it was recognised as a complication of modern psychopharmacology.

Pathophysiology, epidemiology, and impact of migraine

Despite a decade of progress, migraine headache remains prevalent, disabling, underdiagnosed, and undertreated in the United States. Migraine affects approximately 12% of the population, and the economic burden in terms of annual cost of labor lost to migraine disability is between $5.6 and $17.2 billion. The threshold for migraine may be genetically determined, although recent genetic and neurophysiologic studies point to migraine as possibly a channelopathy. Cerebral cortical and brain stem changes occur in migraine. Head pain and associated symptoms of migraine can be explained by activation of the trigeminal vascular system. Evidence has also been accumulated that suggests the release of nitric oxide is an important trigger mechanism. Introduction of the triptans has dramatically advanced acute migraine pharmacotherapy, and preventive therapy has greatly improved; however, public health initiatives may be needed to further advance diagnosis and treatment of this common and disabling disorder.