Neurogenic inflammation in primary headaches

Instrumental assessment of pressure pain threshold over trigeminal and extra-trigeminal area in people with episodic and chronic migraine: a cross-sectional observational study

BACKGROUND

Central and peripheral sensitization are characterized by widespread hyperalgesia that is manifested by larger pain extent area and reduction in pressure pain threshold (PPT). PPT decreases in patients with migraine not only over the trigeminal cervical complex but also throughout the body.

METHODS

A cross-sectional study was adopted to assess the local and widespread hyperalgesia in chronic and episodic migraine patients respect to healthy controls. The guidelines of Andersen's were used to evaluate the PPT bilaterally over 3 muscles in the trigemino-cervical complex (temporalis, sub-occipitalis, trapezius) and over 1 muscle far from this area (tensor fasciae latae).

RESULTS

Thirty subjects with episodic migraine (35.8 ± 2.82 years), 30 with chronic migraine (53.03 ± 19.79 years), and 30 healthy controls (29.06 ± 14.03 years) were enrolled. The interaction effect was present for the trapezius muscle with a significant difference between the right and the left side in episodic group (p = 0.003). A group effect was highlighted in all four muscles analyzed such as suboccipital (p < 0.001), temporalis (p > 0.001), trapezius (p < 0.001), and TFL (p < 0.001). PPT was usually higher in the control group than in the episodic group which in turn was characterized by higher PPT values than the chronic group.

CONCLUSIONS

People with chronic and episodic migraine presented lower PPT than healthy controls both in the trigeminal and in the extra-trigeminal area. People with chronic migraine presented lower PPT than episodic migraine only in the trigeminal area. Temporalis and sub-occipitalis are the most sensitive muscles in people with chronic and episodic migraine.

Vessel-wall MRI in primary headaches: The role of neurogenic inflammation

OBJECTIVE

The purpose of this study was to investigate if vessel-wall magnetic resonance imaging (VW-MRI) could differentiate among primary headaches disorders, such as migraine and cluster headache (CH), and detect the presence of neurogenic inflammation.

BACKGROUND

The pathophysiology of primary headaches disorders is complex and not completely clarified. The activation of nociceptive trigeminal afferents through the release of vasoactive neuropeptides, termed "neurogenic inflammation," has been hypothesized. VW-MRI can identify vessel wall changes, reflecting the inflammatory remodeling of the vessel walls despite different etiologies.

METHODS

In this case series, we enrolled seven patients with migraine and eight patients with CH. They underwent a VW-MRI study before and after the intravenous administration of contrast medium, during and outside a migraine attack or cluster period. Two expert neuroradiologists analyzed the magnetic resonance imaging (MRI) studies to identify the presence of vessel wall enhancement or other vascular abnormalities.

RESULTS

Fourteen out of 15 patients had no enhancement. One out of 15, with migraine, showed a focal parietal enhancement in the intracranial portion of a vertebral artery, unmodified during and outside the attack, thus attributable to atherosclerosis. No contrast enhancement attributable to neurogenic inflammation was observed in VW-MRI, both during and outside the attack/cluster in all patients. Moreover, MRI angiography registered slight diffuse vasoconstriction in one of seven patients with migraine during the attack and in one of eight patients with cluster headache during the cluster period; both patients had taken triptans as symptomatic therapy for pain.

CONCLUSIONS

These preliminary results suggest that VW-MRI studies are negative in patients with primary headache disorders even during migraine attacks or cluster periods. The VW-MRI studies did not detect signs of neurogenic inflammation in the intracranial intradural vessels of patients with migraine or CH.

Steroids in Headache: A Comprehensive Review of Recent Research

Background

Headache is an extremely common symptom of the general outpatient department and also the headache clinic, with prevalence of 48.9% in the general population. None has ever experienced headache in life time. Headache is seen in 1 patient out of 10 general practitioner (GP) consultations, 1 referral out of 3 is headache in neurology OPD, and 1 in 5 of all emergency medical admissions. Of all headaches, around 98% constitute primary headache: migraine without aura, tension headache, and cluster headache. With advancement in various drug modalities, certain headache forms respond less well to the regular approved medications, and some headaches are complicated by the analgesic itself. Steroids have been tried in many subtypes of headache, especially in primary forms of headache with dysautonomia, headache with trigeminal pathway activation and disinhibition, and in certain medication-culprit headaches. This subgroup of headaches is almost a challenge in an emergency for the headache expert as well. So, we need to assess the role of steroids in less well-responsive headaches.

Summary

Current reviewed evidence on the role of steroids in primary headache suggests that steroids have a role in status migrainosus and medication overuse headache when used in the mentioned and monitored manner. Consideration and further exploration of its role in other primary headaches may reveal insight into steroid efficacy as a treatment modality in various subtypes of headache.

Key message

Steroids, when used cautiously in specifically selected primary headaches under supervision, proved miraculous where other modalities failed.

Instrumental assessment of physiotherapy and onabolulinumtoxin-A on cervical and headache parameters in chronic migraine

Introduction

The purpose of the present study is to compare the effect of the physiotherapy to onabolulinumtoxin-A, and their combination, in relation to cervical and headache parameters in patients with chronic migraine.

Methods

This is an observational cohort study conducted by a headache center and a physiotherapy degree course on 30 patients with chronic migraine. The patients were distributed in three groups of treatments for three months: onabolulinumtoxin-A only, physiotherapy only, and onabolulinumtoxin-A plus physiotherapy. The patients were evaluated, before and after each treatment, using the following: the postural assessment software SAPO for the forward head posture; the CROM goniometer for the cervical range of motion; the Migraine Disability Assessment Score for headache parameters.

Results

After 3 months of each treatment, the scores obtained for the headache-related disability and the frequency of migraine decreased significantly for all groups, but the pain intensity scores changed significantly only in the onabolulinumtoxin-A (p = 0.01) and in the onabolulinumtoxin-A plus physiotherapy groups (p = 0.007). On the other hand, the forward head posture was reduced significantly in the physiotherapy (p = 0.002) and in the onabolulinumtoxin-A plus physiotherapy groups (p = 0.003). The cervical range of motion increased significantly in certain directions in the physiotherapy group and in the onabolulinumtoxin-A plus physiotherapy groups.

Conclusions

The physiotherapy improved the cervical parameters. The onabolulinumtoxin-A decreased pain intensity. As a consequence, it can be said that the combined treatment was more useful than a mono-therapy alone. From our results, it can be concluded that onabolulinumtoxin-A plus physiotherapy could be a good option in the management of chronic migraine.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10072-021-05491-w.

Update on the pathophysiology of cluster headache: imaging and neuropeptide studies

OBJECTIVE

Cluster headache (CH) is the most severe primary headache condition. Its pathophysiology is multifaceted and incompletely understood. This review brings together the latest neuroimaging and neuropeptide evidence on the pathophysiology of CH.

METHODS

A review of the literature was conducted by searching PubMed and Web of Science. The search was conducted using the following keywords: imaging studies, voxel-based morphometry, diffusion-tensor imaging, diffusion magnetic resonance imaging, tractography, connectivity, cerebral networks, neuromodulation, central modulation, deep brain stimulation, orexin-A, orexin-B, tract-based spatial statistics, single-photon emission computer tomography studies, positron-emission tomography, functional magnetic resonance imaging, magnetic resonance spectroscopy, trigeminovascular system, neuropeptides, calcitonin gene-related peptide, neurokinin A, substance P, nitric oxide synthase, pituitary adenylate cyclase-activating peptide, vasoactive intestinal peptide, neuropeptide Y, acetylcholine, noradrenaline, and ATP. "Cluster headache" was combined with each keyword for more relevant results. All irrelevant and duplicated records were excluded. Search dates were from October 1976 to May 2018.

RESULTS

Neuroimaging studies support the role of the hypothalamus in CH, as well as other brain areas involved in the pain matrix. Activation of the trigeminovascular system and the release of neuropeptides play an important role in CH pathophysiology. Among neuropeptides, calcitonin gene-related peptide, vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide have been reported to be reliable biomarkers for CH attacks, though not specific for CH. Several other neuropeptides are involved in trigeminovascular activation, but the current evidence does not qualify them as reliable biomarkers in CH.

CONCLUSION

CH has a complex pathophysiology and the pain mechanism is not completely understood. Recent neuroimaging studies have provided insight into the functional and structural network bases of CH pathophysiology. Although there has been important progress in neuropeptide studies, a specific biomarker for CH is yet to be found.

Migraine and Complex Regional Pain Syndrome: A Case-Referent Clinical Study

We studied clinical phenotype differences between migraineurs with CRPS (Mig + CRPS) and those without (Mig − CRPS). Mig + CRPS cases and Mig − CRPS referents aged ≥18 years were enrolled. Diagnosis was made in accordance with International Classification of Headache Disorders-3 beta (ICHD-3 beta) for migraine and Budapest Criteria for CRPS. Migraines both with and without aura were included. A total of 70 Mig + CRPS cases (13% males, mean age 48 years) and 80 Mig − CRPS referents (17% males, mean age 51 years) were included. 33% of Mig + CRPS and 38% of Mig − CRPS exhibited episodic migraine (EM) while 66% of Mig + CRPS and 62% of Mig − CRPS had chronic migraine (CM) (OR = 0.98, CI 0.36, 2.67). Median duration of CRPS was 3 years among EM + CRPS and 6 years among CM + CRPS cohort (p < 0.02). Mig + CRPS (57%) carried higher psychological and medical comorbidities compared to Mig − CRPS (6%) (OR 16.7, CI 10.2, 23.6). Higher migraine frequency was associated with longer CRPS duration. Migraineurs who developed CRPS had higher prevalence of psychological and medical disorders. Alleviating migraineurs' psychological and medical comorbidities may help lower CRPS occurrence.

Migraine Pathophysiology and its Clinical Implications

The vascular hypothesis of migraine has now been superseded by a more integrated theory that involves both vascular and neuronal components. It has been demonstrated that the visual aura experienced by some migraineurs arises from cortical spreading depression, and that this neuronal event may also activate perivascular nerve afferents, leading to vasodilation and neurogenic inflammation of the meningeal blood vessels and, thus, throbbing pain. The involvement of the parasympathetic system supplying the meninges also causes increased vasodilation and pain. As an acute attack progresses, sensory neurones in the trigeminal nucleus caudalis become sensitized, resulting in the phenomenon of cutaneous allodynia. Triptans may act at several points during the progression of a migraine attack. However, the development of central sensitization impacts upon the effectiveness of triptan therapy.

What is the evidence for the use of corticosteroids in migraine?

Corticosteroids are widely prescribed for the management of migraine attacks. The earliest clinical studies examining the efficacy of corticosteroid monotherapy for managing migraine attacks date back to 1952. Since then, 26 heterogeneous clinical studies and four meta-analyses have been conducted to assess the efficacy of corticosteroids in either aborting acute migraine attacks, prolonged migraine attacks or recurrent headaches. Most of these (86 %) studies employed different comparator arms with corticosteroids monotherapy administration while some studies (14 %) evaluated adjunctive corticosteroid therapy. The majority of these clinical studies revealed the superior efficacy of corticosteroids as mono- or adjunctive-therapy both for recurrent and acute migraine attacks, while the remaining showed non-inferior efficacy. Different forms of oral and parenteral corticosteroids in either single-dose or short-tapering schedules are prescribed; there are clinical studies supporting the efficacy of both methods. Corticosteroids can be administered safely up to six times annually. Corticosteroids are also useful in managing patients who frequent emergency departments with "medication-seeking behavior." Migraine patients with refractory headaches, history of recurrent headaches, severe baseline disability, and status migrainosus were found to have the most beneficial response from corticosteroid therapy.

The place of corticosteroids in migraine attack management: A 65-year systematic review with pooled analysis and critical appraisal

BACKGROUND AND OBJECTIVES

Headaches recur in up to 87% of migraine patients visiting the emergency department (ED), making ED recidivism a management challenge. We aimed herein to determine the role of corticosteroids in the acute management of migraine in the ED and outpatient care.

METHODS

Advanced search strategies employing PubMed/MEDLINE, Web of Science, and Cochrane Library databases inclusive of a relevant gray literature search was employed for Clinical Studies and Systematic Reviews by combining the terms "migraine" and "corticosteroids" spanning all previous years since the production of synthetic corticosteroids ca. 1950 until August 30, 2014. Methods were in accordance with MOOSE guidelines.

RESULTS

Twenty-five studies (n = 3989, median age 37.5 years, interquartile range or IQR 35-41 years; median male:female ratio 1:4.23, IQR 1:2.1-6.14; 52% ED-based, 56% randomized-controlled) and four systematic reviews were included. International Classification of Headache Disorders criteria were applied in 64%. Nineteen studies (76%) indicated observed outcome differences favoring benefits of corticosteroids, while six (24%) studies indicated non-inferior outcomes for corticosteroids. Median absolute risk reduction was 30% (range 6%-48.2%), and 11% (6%-48.6%) for 24-, and 72-hour headache recurrence, respectively. Parenteral dexamethasone was the most commonly (56%) administered steroid, at a median single dose of 10 mg (range 4-24 mg). All meta-analyses revealed efficacy of adjuvant corticosteroids to various abortive medications-indicating generalizability. Adverse effects were tolerable. Higher disability, status migrainosus, incomplete pain relief, and previous history of headache recurrence predicted outcome favorability.

CONCLUSIONS

Our literature review suggests that with corticosteroid treatment, recurrent headaches become milder than pretreated headaches and later respond to nonsteroidal therapy. Single-dose intravenous dexamethasone is a reasonable option for managing resistant, severe, or prolonged migraine attacks.

Propofol alleviates intractable migraine headache: a case report

Abstract

Several medications have been proposed as the first line drugs in the treatment of migraine attack. However, the low efficacy, potential complications of medications and the intolerance of some patients for oral route due to nausea and vomiting establish a difficult situation in some migraine patients. This report describes a dramatic pain relief with 60 mg of intravenous propofol in a patient with migraine attack refractory to treatment with metoclopramide, promethazine, dexamethasone and meperidine. Pain relief in this patient besides earlier case reports suggests that subanesthetic doses of propofol may be an alternative to other treatment modalities for acute migraine.

Role of nitric oxide in cluster headache

Nitric oxide (NO) is an important molecule in headache pathophysiology. NO regulates vascular tone and acts as a potent vasodilator, and thus participates in regulating blood flow. NO is also considered to play a role in processing sensory information and pain sensitization. In this article, we review the role of NO in one of the primary headache disorders, cluster headache (CH). The pathophysiology of CH is still not completely understood. A multifactorial genesis where NO is likely to be involved is probable. The level of NO production has been shown to correlate with disease activity in several inflammatory disorders, such as cystitis, multiple sclerosis, and cerebral lupus erythematosus. In this article, the issue of whether similar circumstances apply for CH and also the role of NO in the pathophysiology of CH in a wider perspective are discussed.

A new animal model of trigeminal neuralgia produced by administration of cobra venom to the infraorbital nerve in the rat

BACKGROUND

Understanding the mechanism of trigeminal neuralgia may be elucidated by developing laboratory animal models that closely mimic the features of this specific type of neuropathic pain. We have developed an experimental animal model for trigeminal neuralgia using a technique of injecting cobra venom into the infraorbital nerve (ION) trunk.

METHODS

Male Sprague-Dawley rats were subjected to the administration of cobra venom or saline into the ION trunk. Mechanical stimuli were applied to the ION territory in consecutive days after surgery. Mechanical thresholds were measured over a 90-day period on the bilateral facial region. Vascular permeability in the ION territory was measured using Evans blue dye.

RESULTS

The cobra venom-treated rats developed mechanical allodynia 3 days after surgery that lasted for 60 days postoperatively at the ipsilateral side. The mechanical thresholds of the contralateral ION territory also showed a profound decrease but were sustained for only approximately 30 days. There was no change of mechanical thresholds in the control groups. The extravasation of Evans blue increased significantly in the skin after administration of cobra venom to the ION compared with control rats (P < 0.05).

CONCLUSION

The cobra venom model may provide a reasonable model for investigating the mechanism of trigeminal neuropathic pain.

Migraine surgery: a plastic surgery solution for refractory migraine headache

Migraine headache can be a debilitating condition that confers a substantial burden to the affected individual and to society. Despite significant advancements in the medical management of this challenging disorder, clinical data have revealed a proportion of patients who do not adequately respond to pharmacologic intervention and remain symptomatic. Recent insights into the pathogenesis of migraine headache argue against a central vasogenic cause and substantiate a peripheral mechanism involving compressed craniofacial nerves that contribute to the generation of migraine headache. Botulinum toxin injection is a relatively new treatment approach with demonstrated efficacy and supports a peripheral mechanism. Patients who fail optimal medical management and experience amelioration of headache pain after injection at specific anatomical locations can be considered for subsequent surgery to decompress the entrapped peripheral nerves. Migraine surgery is an exciting prospect for appropriately selected patients suffering from migraine headache and will continue to be a burgeoning field that is replete with investigative opportunities.

Headache in thrombotic thrombocytopenic purpura: two cases with pathophysiological considerations

Headache is one of the most common neurological symptoms reported by patients with thrombotic thrombocytopenic purpura (TTP). Reports of headache characteristics in patients with TTP are rare. We report 2 cases of headache in a setting of TTP and review previous reports. Headache in TTP can have features in common with both migraine and tension-type headache. Although the pathophysiology of headache in TTP is not certain, platelet aggregation and activation may play a key role.

Medical history and the onset of complex regional pain syndrome (CRPS)

Knowledge concerning the medical history prior to the onset of complex regional pain syndrome (CRPS) might provide insight into its risk factors and potential underlying disease mechanisms. To evaluate prior to CRPS medical conditions, a case-control study was conducted in the Integrated Primary Care Information (IPCI) project, a general practice (GP) database in the Netherlands. CRPS patients were identified from the records and validated through examination by the investigator (IASP criteria) or through specialist confirmation. Cases were matched to controls on age, gender and injury type. All diagnoses prior to the index date were assessed by manual review of the medical records. Some pre-specified medical conditions were studied for their association with CRPS, whereas all other diagnoses, grouped by pathogenesis, were tested in a hypothesis-generating approach. Of the identified 259 CRPS patients, 186 cases (697 controls) were included, based on validation by the investigator during a visit (102 of 134 visited patients) or on specialist confirmation (84 of 125 unvisited patients). A medical history of migraine (OR: 2.43, 95% CI: 1.18-5.02) and osteoporosis (OR: 2.44, 95% CI: 1.17-5.14) was associated with CRPS. In a recent history (1-year before CRPS), cases had more menstrual cycle-related problems (OR: 2.60, 95% CI: 1.16-5.83) and neuropathies (OR: 5.7; 95% CI: 1.8-18.7). In a sensitivity analysis, including only visited cases, asthma (OR: 3.0; 95% CI: 1.3-6.9) and CRPS were related. Psychological factors were not associated with CRPS onset. Because of the hypothesis-generating character of this study, the findings should be confirmed by other studies.

Neurovascular pains: implications of migraine for the oral and maxillofacial surgeon

Epidemiologic studies have shown that migraine headaches are a common finding in the general population, often associated with a high degree of disability. Additionally, migraine has a reported comorbidity with other medical conditions, most notably with chronic pains, such as temporomandibular disorders. The pathophysiologic mechanisms involved with migraine are suggestive of an increased and prolonged hyperexcitability to stimuli, especially within the trigeminal distribution. Because migraine is mediated by branches of the trigeminal nerve it has the potential to mimic other types of pains, such as toothache or sinusitis. It is therefore recommended that oral and maxillofacial surgeons be familiar with the diagnostic criteria for migraine headaches to identify and appropriately treat such individuals who present to their clinics.

Neurovascular pharmacology of migraine

Migraine is a paroxysmal neurovascular disorder, which affects a significant proportion of the population. Since dilation of cranial blood vessels is likely to be responsible for the headache experienced in migraine, many experimental models for the study of migraine have focussed on this feature. The current review discusses a model that is based on the constriction of carotid arteriovenous anastomoses in anaesthetized pigs, which has during the last decades proven of great value in identifying potential antimigraine drugs acting via a vascular mechanism. Further, the use of human isolated blood vessels in migraine research is discussed. Thirdly, we describe an integrated neurovascular model, where dural vasodilatation in response to trigeminal perivascular nerve stimulation can be studied. Such a model not only allows an in-depth characterization of directly vascularly acting drugs, but also of drugs that are supposed to act via inhibition of vasodilator responses to endogenous neuropeptides, or of drugs that inhibit the release of these neuropeptides. We discuss the use of this model in a study on the influence of female sex hormones on migraine. Finally, the implementation of this model in mice is considered. Such a murine model allows the use of genetically modified animals, which will lead to a better understanding of the ion channel mutations that are found in migraine patients.

Transcranial direct current stimulation reveals inhibitory deficiency in migraine

The issue of interictal excitability of cortical neurons in migraine patients is controversial: some studies have reported hypo-, others hyperexcitability. The aim of the present study was to observe the dynamics of this basic interictal state by further modulating the excitability level of the visual cortex using transcranial direct current stimulation (tDCS) in migraineurs with and without aura. In healthy subjects anodal tDCS decreases, cathodal stimulation increases transcranial magnetic stimulation (TMS)-elicited phosphene thresholds (PT), which is suggested as a representative value of visual cortex excitability. Compared with healthy controls, migraine patients tended to show lower baseline PT values, but this decrease failed to reach statistical significance. Anodal stimulation decreased phosphene threshold in migraineurs similarly to controls, having a larger effect in migraineurs with aura. Cathodal stimulation had no significant effect in the patient groups. This result strengthens the notion of deficient inhibitory processes in the cortex of migraineurs, which is selectively revealed by activity-modulating cortical input.

Could statins be useful in the treatment of patients with migraine?

Migraine is a common and disabling neurological disorder. Studies have shown that patients with migraine (especially those with typical aura with migraine) have an unfavorable cardiovascular risk profile and an increased risk of early-onset (<45 years) ischemic stroke. Statins are effective hypolipidemic drugs that reduce cardiovascular-related morbidity and death in patients with or without established atherosclerotic vascular disease. We report a patient whose frequent attacks of typical aura with migraine completely resolved after the initiation of treatment with a statin. In this context, we comment on the possible effects of statins on the pathophysiology of migraine. We suggest that statins may be useful drugs in the treatment of migraine because they could reduce the increased cardiovascular risk in these patients and also attenuate migraine attacks. Only a randomized prospective study in this population could provide a definite answer to these speculations.

The Inhibitory Effects of Local Anesthetics on Primary Sensory Nerve and Parasympathetic Nerve in Rabbit Eye

Primary sensory nerves transmit information to both the periphery and central nervous systems, and they mediate neurogenic inflammation by release of neurotransmitters, such as tachykinins, in the periphery. Because the effect of local anesthetics on neurogenic inflammation is a subject of controversy, we investigated the direct effect of local anesthetics on tachykininergic neurotransmission, comparing it with cholinergic neurotransmission in the rabbit iris sphincter muscle. Rabbit iris sphincter muscle is innervated by trigeminal tachykininergic and parasympathetic cholinergic nerves, and the electrical transmural stimulation produces tachykininergic and cholinergic contractions. Cocaine and lidocaine (1-300 microM) attenuated tachykininergic and cholinergic contractions induced by electrical transmural stimulation in concentration- and stimulus frequency-dependent manner. However, the sensitivity to both local anesthetics was slightly, but significantly, higher in tachykininergic than in cholinergic responses. Exogenous neurokinin A and carbachol produced contractions that were not inhibited by 100 microM of cocaine and lidocaine. These results show that local anesthetics have a direct inhibitory effect on tachykininergic neurotransmission of the trigeminal sensory nerve, and the effect on this nerve is more potent than on the parasympathetic nerve and suggests that local anesthetics may have antineurogenic inflammatory effects via the inhibitory effects on the peripheral transmission of primary sensory nerve.

Experimental migraine models and their relevance in migraine therapy

Although the understanding of migraine pathophysiology is incomplete, it is now well accepted that this neurovascular syndrome is mainly due to a cranial vasodilation with activation of the trigeminal system. Several experimental migraine models, based on vascular and neuronal involvement, have been developed. Obviously, the migraine models do not entail all facets of this clinically heterogeneous disorder, but their contribution at several levels (molecular, in vitro, in vivo) has been crucial in the development of novel antimigraine drugs and in the understanding of migraine pathophysiology. One important vascular in vivo model, based on an assumption that migraine headache involves cranial vasodilation, determines porcine arteriovenous anastomotic blood flow. Other models utilize electrical stimulation of the trigeminal ganglion/nerve to study neurogenic dural inflammation, while the superior sagittal sinus stimulation model takes into account the transmission of trigeminal nociceptive input in the brainstem. More recently, the introduction of integrated models, namely electrical stimulation of the trigeminal ganglion or systemic administration of capsaicin, allows studying the activation of the trigeminal system and its effect on the cranial vasculature. Studies using in vitro models have contributed enormously during the preclinical stage to characterizing the receptors in cranial blood vessels and to studying the effects of several putative antimigraine agents. The aforementioned migraine models have advantages as well as some limitations. The present review is devoted to discussing various migraine models and their relevance to antimigraine therapy.

Valdecoxib for treatment of a single, acute, moderate to severe migraine headache

OBJECTIVE

To evaluate the analgesic efficacy and safety of a single 20- or 40-mg dose of valdecoxib compared with placebo in treatment of a single, acute, moderate or severe migraine headache, with or without aura.

BACKGROUND

Valdecoxib, an oral COX-2 specific inhibitor, is indicated for relief of the signs and symptoms of rheumatoid arthritis and osteoarthritis and treatment of primary dysmenorrhea. This study assessed the optimal dose of valdecoxib for treatment of a single, acute, moderate to severe migraine headache.

METHODS

This was a double-blind, randomized, placebo- and active-controlled, multicenter, single-dose (primary end point) and multiple-dose (secondary end point), 56-day study of valdecoxib in the treatment of a single, acute, moderate or severe migraine headache, with or without aura. Migraine headaches were diagnosed according to International Headache Society (IHS) criteria. The primary efficacy end point was headache response (defined as reduction of headache pain intensity from moderate or severe to mild or none) at 2 hours postdose. Patients assessed their headache pain intensity and presence or absence of migraine-associated nausea, vomiting, phonophobia, and photophobia at intervals from 0 to 24 hours postdose. Sumatriptan 50 mg (encapsulated, in standard method, to maintain blinding) was included as a positive control for assay sensitivity. No statistical comparisons were performed between active treatment arms (valdecoxib 20 mg, valdecoxib 40 mg, and sumatriptan 50 mg). Adverse events and safety parameters were monitored throughout the study.

RESULTS

In the intent-to-treat population of 570 patients (135 valdecoxib 20 mg, 151 valdecoxib 40 mg, 143 sumatriptan, and 141 placebo), no significant differences in baseline demographics among treatment groups were observed. The headache response rate with valdecoxib 40 mg and sumatriptan 50 mg was significantly greater than that with placebo at all time points from 2 to 24 hours postdose. With valdecoxib 20 mg, headache response rate was significantly greater than placebo from 2 to 4 hours. Significantly fewer patients treated with valdecoxib 40 mg, compared with placebo, experienced nausea, vomiting, and phonophobia at 2 hours postdose.

CONCLUSIONS

A single 40-mg dose of valdecoxib is effective and well tolerated in treatment of migraine headache pain and associated symptoms.

The role of mast cells in migraine pathophysiology

Mast cells are critical players in allergic reactions, but they have also been shown to be important in immunity and recently also in inflammatory diseases, especially asthma. Migraines are episodic, typically unilateral, throbbing headaches that occur more frequently in patients with allergy and asthma implying involvement of meningeal and/or brain mast cells. These mast cells are located perivascularly, in close association with neurons especially in the dura, where they can be activated following trigeminal nerve, as well as cervical or sphenopalatine ganglion stimulation. Neuropeptides such as calcitonin gene-related peptide (CGRP), hemokinin A, neurotensin (NT), pituitary adenylate cyclase activating peptide (PACAP), and substance P (SP) activate mast cells leading to secretion of vasoactive, pro-inflammatory, and neurosensitizing mediators, thereby contributing to migraine pathogenesis. Brain mast cells can also secrete pro-inflammatory and vasodilatory molecules such as interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF), selectively in response to corticotropin-releasing hormone (CRH), a mediator of stress which is known to precipitate or exacerbate migraines. A better understanding of brain mast cell activation in migraines would be useful and could lead to several points of prophylactic intervention.

Calcitonin gene-related peptide and its role in migraine pathophysiology

Migraine is a common neurological disorder that is associated with an increase in plasma calcitonin gene-related peptide (CGRP) levels. CGRP, a neuropeptide released from activated trigeminal sensory nerves, dilates intracranial blood vessels and transmits vascular nociception. Therefore, it is propounded that: (i) CGRP may have an important role in migraine pathophysiology, and (ii) inhibition of trigeminal CGRP release or CGRP-induced cranial vasodilatation may abort migraine. In this regard, triptans ameliorate migraine headache primarily by constricting the dilated cranial blood vessels and by inhibiting the trigeminal CGRP release. In order to explore the potential role of CGRP in migraine pathophysiology, the advent of a selective CGRP receptor antagonist was obligatory. The introduction of di-peptide CGRP receptor antagonists, namely BIBN4096BS (1-piperidinecarboxamide, N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl] pentyl] amino]-1-[(3,5-dibromo-4-hydroxyphenyl) methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-, [R-(R*,S*)]-), is a breakthrough in CGRP receptor pharmacology and can be used as a tool to investigate the role of CGRP in migraine headaches. Preclinical investigations in established migraine models that are predictive of antimigraine activity have shown that BIBN4096BS is a potent CGRP receptor antagonist and that it has antimigraine potential. Indeed, a recently published clinical study has reported that BIBN409BS is effective in treating acute migraine attacks without significant side effects. The present review will discuss mainly the potential role of CGRP in the pathophysiology of migraine and the various treatment modalities that are currently available to target this neuropeptide.