Migraine and the blood-brain barrier

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus is a critical brain substrate for learning and memory; events that harm the hippocampus can seriously impair mental and behavioral functioning. Hippocampal pathophysiologies have been identified as potential causes and effects of a remarkably diverse array of medical diseases, psychological disorders, and environmental sources of damage. It may be that the hippocampus is more vulnerable than other brain areas to insults that are related to these conditions. One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults. Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain, and that developing interventions that protect the hippocampal BBB may help to prevent or ameliorate the harmful effects of many insults on memory and cognition.

Increased iron deposition in nucleus accumbens associated with disease progression and chronicity in migraine

BACKGROUND

Migraine is one of the world's most prevalent and disabling diseases. Despite huge advances in neuroimaging research, more valuable neuroimaging markers are still urgently needed to provide important insights into the brain mechanisms that underlie migraine symptoms. We therefore aim to investigate the regional iron deposition in subcortical nuclei of migraineurs as compared to controls and its association with migraine-related pathophysiological assessments.

METHODS

A total of 200 migraineurs (56 chronic migraine [CM], 144 episodic migraine [EM]) and 41 matched controls were recruited. All subjects underwent MRI and clinical variables including frequency/duration of migraine, intensity of migraine, 6-item Headache Impact Test (HIT-6), Migraine Disability Assessment (MIDAS), and Pittsburgh Sleep Quality Index (PSQI) were recorded. Quantitative susceptibility mapping was employed to quantify the regional iron content in subcortical regions. Associations between clinical variables and regional iron deposition were studied as well.

RESULTS

Increased iron deposition in the putamen, caudate, and nucleus accumbens (NAC) was observed in migraineurs more than controls. Meanwhile, patients with CM had a significantly higher volume of iron deposits compared to EM in multiple subcortical nuclei, especially in NAC. Volume of iron in NAC can be used to distinguish patients with CM from EM with a sensitivity of 85.45% and specificity of 71.53%. As the most valuable neuroimaging markers in all of the subcortical nuclei, higher iron deposition in NAC was significantly associated with disease progression, and higher HIT-6, MIDAS, and PSQI.

CONCLUSIONS

These findings provide evidence that iron deposition in NAC may be a biomarker for migraine chronicity and migraine-related dysfunctions, thus may help to understand the underlying vascular and neural mechanisms of migraine.

TRIAL REGISTRATION

ClinicalTrials.gov, number NCT04939922.

Brain barriers and their potential role in migraine pathophysiology

Migraine is a ubiquitous neurologic disease that afflicts people of all ages. Its molecular pathogenesis involves peptides that promote intracranial vasodilation and modulate nociceptive transmission upon release from sensory afferents of cells in the trigeminal ganglion and parasympathetic efferents of cells in the sphenopalatine ganglion. Experimental data have confirmed that intravenous infusion of these vasoactive peptides induce migraine attacks in people with migraine, but it remains a point of scientific contention whether their site of action lies outside or within the central nervous system. In this context, it has been hypothesized that transient dysfunction of brain barriers before or during migraine attacks might facilitate the passage of migraine-inducing peptides into the central nervous system. Here, we review evidence suggestive of brain barrier dysfunction in migraine pathogenesis and conclude with lessons learned in order to provide directions for future research efforts.

Pharmacological treatment of migraine: CGRP and 5-HT beyond the triptans

Migraine is a highly disabling neurovascular disorder characterized by a severe headache (associated with nausea, photophobia and/or phonophobia), and trigeminovascular system activation involving the release of calcitonin-gene related peptide (CGRP). Novel anti-migraine drugs target CGRP signaling through either stimulation of 5-HT1F receptors on trigeminovascular nerves (resulting in inhibition of CGRP release) or direct blockade of CGRP or its receptor. Lasmiditan is a highly selective 5-HT1F receptor agonist and, unlike the triptans, is devoid of vasoconstrictive properties, allowing its use in patients with cardiovascular risk. Since lasmiditan can actively penetrate the blood-brain barrier, central therapeutic as well as side effects mediated by 5-HT1F receptor activation should be further investigated. Other novel anti-migraine drugs target CGRP signaling directly. This neuropeptide can be targeted by the monoclonal antibodies eptinezumab, fremanezumab and galcanezumab, or by CGRP-neutralizing L-aptamers called Spiegelmers. The CGRP receptor can be targeted by the monoclonal antibody erenumab, or by small-molecule antagonists called gepants. Currently, rimegepant and ubrogepant have been developed for acute migraine treatment, while atogepant is studied for migraine prophylaxis. Of these drugs targeting CGRP signaling directly, eptinezumab, erenumab, fremanezumab, galcanezumab, rimegepant and ubrogepant have been approved for clinical use, while atogepant is in the last stage before approval. Although all of these drugs seem highly promising for migraine treatment, their safety should be investigated in the long-term. Moreover, the exact mechanism(s) of action of these drugs need to be elucidated further, to increase both safety and efficacy and to increase the number of responders to the different treatments, so that all migraine patients can satisfactorily be treated.

Altered regional cerebral blood flow and hypothalamic connectivity immediately prior to a migraine headache

BACKGROUND

There is evidence of altered resting hypothalamic activity patterns and connectivity prior to a migraine, however it remains unknown if these changes are driven by changes in overall hypothalamic activity levels. If they are, it would corroborate the idea that changes in hypothalamic function result in alteration in brainstem pain processing sensitivity, which either triggers a migraine headache itself or allows an external trigger to initiate a migraine headache. We hypothesise that hypothalamic activity increases immediately prior to a migraine headache and this is accompanied by altered functional connectivity to pain processing sites in the brainstem.

METHODS

In 34 migraineurs and 26 healthy controls, we collected a series comprising 108 pseudo-continuous arterial spin labelling images and 180 gradient-echo echo planar resting-state functional magnetic resonance volumes to measure resting regional cerebral blood flow and functional connectivity respectively. Images were pre-processed and analysed using custom SPM12 and Matlab software.

RESULTS

Our results reflect that immediately prior to a migraine headache, resting regional cerebral blood flow decreases in the lateral hypothalamus. In addition, resting functional connectivity strength decreased between the lateral hypothalamus and important regions of the pain processing pathway, such as the midbrain periaqueductal gray, dorsal pons, rostral ventromedial medulla and cingulate cortex, only during this critical period before a migraine headache.

CONCLUSION

These data suggest altered hypothalamic function and connectivity in the period immediately prior to a migraine headache and supports the hypothesis that the hypothalamus is involved in migraine initiation.

Spreading depolarizations trigger caveolin-1-dependent endothelial transcytosis

OBJECTIVE

Cortical spreading depolarizations (CSDs) are intense and ubiquitous depolarization waves relevant for the pathophysiology of migraine and brain injury. CSDs disrupt the blood-brain barrier (BBB), but the mechanisms are unknown.

METHODS

A total of six CSDs were evoked over 1 hour by topical application of 300 mM of KCl or optogenetically with 470 nm (blue) LED over the right hemisphere in anesthetized mice (C57BL/6 J wild type, Thy1-ChR2-YFP line 18, and cav-1-/- ). BBB disruption was assessed by Evans blue (2% EB, 3 ml/kg, intra-arterial) or dextran (200 mg/kg, fluorescein, 70,000 MW, intra-arterial) extravasation in parietotemporal cortex at 3 to 24 hours after CSD. Endothelial cell ultrastructure was examined using transmission electron microscopy 0 to 24 hours after the same CSD protocol in order to assess vesicular trafficking, endothelial tight junctions, and pericyte integrity. Mice were treated with vehicle, isoform nonselective rho-associated kinase (ROCK) inhibitor fasudil (10 mg/kg, intraperitoneally 30 minutes before CSD), or ROCK-2 selective inhibitor KD025 (200 mg/kg, per oral twice-daily for 5 doses before CSD).

RESULTS

We show that CSD-induced BBB opening to water and large molecules is mediated by increased endothelial transcytosis starting between 3 and 6 hours and lasting approximately 24 hours. Endothelial tight junctions, pericytes, and basement membrane remain preserved after CSDs. Moreover, we show that CSD-induced BBB disruption is exclusively caveolin-1-dependent and requires rho-kinase 2 activity. Importantly, hyperoxia failed to prevent CSD-induced BBB breakdown, suggesting that the latter is independent of tissue hypoxia.

INTERPRETATION

Our data elucidate the mechanisms by which CSDs lead to transient BBB disruption, with diagnostic and therapeutic implications for migraine and brain injury.

Region-specific disruption of the blood-brain barrier following repeated inflammatory dural stimulation in a rat model of chronic trigeminal allodynia

Background The blood-brain barrier (BBB) has been hypothesized to play a role in migraine since the late 1970s. Despite this, limited investigation of the BBB in migraine has been conducted. We used the inflammatory soup rat model of trigeminal allodynia, which closely mimics chronic migraine, to determine the impact of repeated dural inflammatory stimulation on BBB permeability. Methods The sodium fluorescein BBB permeability assay was used in multiple brain regions (trigeminal nucleus caudalis (TNC), periaqueductal grey, frontal cortex, sub-cortex, and cortex directly below the area of dural activation) during the episodic and chronic stages of repeated inflammatory dural stimulation. Glial activation was assessed in the TNC via GFAP and OX42 immunoreactivity. Minocycline was tested for its ability to prevent BBB disruption and trigeminal sensitivity. Results No astrocyte or microglial activation was found during the episodic stage, but BBB permeability and trigeminal sensitivity were increased. Astrocyte and microglial activation, BBB permeability, and trigeminal sensitivity were increased during the chronic stage. These changes were only found in the TNC. Minocycline treatment prevented BBB permeability modulation and trigeminal sensitivity during the episodic and chronic stages. Discussion Modulation of BBB permeability occurs centrally within the TNC following repeated dural inflammatory stimulation and may play a role in migraine.

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.

The Role of Adenosine Signaling in Headache: A Review

Migraine is the third most prevalent disease on the planet, yet our understanding of its mechanisms and pathophysiology is surprisingly incomplete. Recent studies have built upon decades of evidence that adenosine, a purine nucleoside that can act as a neuromodulator, is involved in pain transmission and sensitization. Clinical evidence and rodent studies have suggested that adenosine signaling also plays a critical role in migraine headache. This is further supported by the widespread use of caffeine, an adenosine receptor antagonist, in several headache treatments. In this review, we highlight evidence that supports the involvement of adenosine signaling in different forms of headache, headache triggers, and basic headache physiology. This evidence supports adenosine A_2A receptors as a critical adenosine receptor subtype involved in headache pain. Adenosine A_2A receptor signaling may contribute to headache via the modulation of intracellular Cyclic adenosine monophosphate (cAMP) production or 5' AMP-activated protein kinase (AMPK) activity in neurons and glia to affect glutamatergic synaptic transmission within the brainstem. This evidence supports the further study of adenosine signaling in headache and potentially illuminates it as a novel therapeutic target for migraine.

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.

Serum MicroRNA Signatures in Migraineurs During Attacks and in Pain-Free Periods

MicroRNAs have emerged as important biomarkers and modulators of pathophysiological processes including oncogenesis and neurodegeneration. MicroRNAs are found to be involved in the generation and maintenance of pain in animal models of inflammation and neuropathic pain. Recently, microRNA dysregulation has been reported in patients with painful conditions such as complex regional pain syndrome and fibromyalgia. The aim of this study was to assess whether serum microRNA alterations occur during migraine attacks and whether migraine manifests in chronic serum microRNA aberrations. Two cohorts of 24 migraineurs, and age- and sex-matched healthy controls were included. High-content serum microRNA (miRNA) arrays were used to assess the serum microRNA profiles of migraineurs during attacks and pain-free periods in comparison with healthy controls. Of the 372 assessed microRNAs, 32 or ≈ 8% were found to be differentially expressed and 4 of these--miR-34a-5p, 29c-5p, -382-5p, and -26b-3p--were selected for further investigation. Migraine attacks were associated with an acute upregulation in miR-34a-5p and miR-382-5p expression. Interestingly, miR-382-5p not only exhibited an upregulation during attack but also proved to be a biomarker for migraine when comparing migraineurs in pain-free periods to the healthy control group (p = <0.01). In conclusion, migraine manifestation is reflected in serum miRNA aberrations, both during attacks and pain-free periods. This finding sheds light on the potential role of microRNAs in the pathophysiology of migraine and adds a new approach towards potential identification of much sought-after serum biomarkers of migraine.

The neurobiology of migraine

The understanding of migraine has moved well beyond its traditional characterization as a "vascular headache." In considering the basic neurobiology of migraine, it is important to begin with the concept of migraine as not merely a headache, but rather a heterogeneous array of episodic symptoms. Among the array of phenomena experienced by migraine patients are visual disturbances, nausea, cognitive dysfunction, fatigue, and sensitivity to light, sound, smell, and touch. These symptoms may occur independently or in any combination, and in some patients occur even in the absence of headache. The diversity and variability of symptoms experienced by migraine patients belies a complex neurobiology, involving multiple cellular, neurochemical, and neurophysiological processes occurring at multiple neuroanatomical sites. Migraine is a multifaceted neurobiological phenomenon that involves activation of diverse neurochemical and cellular signaling pathways in multiple regions of the brain. Propagated waves of cellular activity in the cortex, possibly involving distinct glial and vascular signaling mechanisms, can occur along with activation of brainstem centers and nociceptive pathways. Whether different brain regions become involved in a linear sequence, or as parallel processes, is uncertain. The modulation of brain signaling by genetic factors, and by sex and sex hormones, provides important clues regarding the fundamental mechanisms by which migraine is initiated and sustained. Each of these mechanisms may represent distinct therapeutic targets for this complex and commonly disabling disorder.

Revisiting the efficacy of sumatriptan therapy during the aura phase of migraine

OBJECTIVE

To reexamine the efficacy of terminating migraine headache by administration of sumatriptan during the visual-aura phase of the attack. Background.- Although the antimigraine action of triptans is most effective soon after onset of the headache, treatment during the aura phase has been found to be ineffective.

METHODS

Nineteen subjects having migraine with aura were studied using a 4-way crossover, open-label design. Each patient was asked to treat 8 consecutive attacks with 100 mg of sumatriptan RT: 3 attacks treated at a timing of the patient's discretion (baseline); 1 attack treated 4 hours after onset of pain (late); 2 attacks treated within 1 hour of onset of pain (early); 2 attacks treated during the aura phase - before the onset of pain (aura). Pain level and cutaneous allodynia were reported by the patients at the onset of pain, at the time of treatment, and 2 and 24 hours after treatment.

RESULTS

Sumatriptan treatment during the aura preempted the development of headache in 34/38 (89%) attacks. The same patients were rendered pain-free in 30/38 (79%) of attacks treated within 1 hour of pain onset, and in 4/19 (21%) of attacks treated 4 hours after the onset of pain. The incidence of allodynia at the time of treatment was 2/38 (5%) in attacks treated during aura, 8/38 (21%) in attacks treated early, and 14/19 (74%) in attacks treated late.

CONCLUSION

Considering the discrepancy between the present and previous clinical studies, it is worthwhile revisiting the efficacy of preemptive triptan therapy during the aura phase of migraine attacks, using larger-scale, 3-way, crossover, placebo-controlled studies.

Migraine treatment with calcium channel blockers

Irrespective of their mechanism of action, which so far has not been clarified, calcium channel blockers (CCBs) have a documented prophylactic effect on classical and common migraine, as well as on cluster headache. The drugs may reduce migraine prodromes, the frequency of migraine attacks, and also decrease the severity and possibly the duration of these attacks. Notably, their optimum effect is often seen after more than 2 months of treatment. Side effects seem to be few and mild. Whether or not there are differences in therapeutic efficacy between different CCBs is presently unclear. As comparisons with other alternatives of treatment are sparse, the place of CCBs in migraine therapy remains to be established.

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.

Donitriptan, but not sumatriptan, inhibits capsaicin-induced canine external carotid vasodilatation via 5-HT1B rather than 5-HT1D receptors

BACKGROUND AND PURPOSE

It has been suggested that during a migraine attack capsaicin-sensitive trigeminal sensory nerves release calcitonin gene-related peptide (CGRP), resulting in cranial vasodilatation and central nociception; hence, trigeminal inhibition may prevent this vasodilatation and abort migraine headache. This study investigated the effects of the agonists sumatriptan (5-HT(1B/1D) water-soluble), donitriptan (5-HT(1B/1D) lipid-soluble), PNU-142633 (5-HT(1D) water-soluble) and PNU-109291 (5-HT(1D) lipid-soluble) on vasodilator responses to capsaicin, alpha-CGRP and acetylcholine in dog external carotid artery.

EXPERIMENTAL APPROACH

59 vagosympathectomized dogs were anaesthetized with sodium pentobarbitone. Blood pressure and heart rate were recorded with a pressure transducer, connected to a cannula inserted into a femoral artery. A precalibrated flow probe was placed around the common carotid artery, with ligation of the internal carotid and occipital branches, and connected to an ultrasonic flowmeter. The thyroid artery was cannulated for infusion of agonists.

KEY RESULTS

Intracarotid infusions of capsaicin, alpha-CGRP and acetylcholine dose-dependently increased blood flow through the carotid artery. These responses remained unaffected after intravenous (i.v.) infusions of sumatriptan, PNU-142633, PNU-109291 or physiological saline; in contrast, donitriptan significantly attenuated the vasodilator responses to capsaicin, but not those to alpha-CGRP or acetylcholine. Only sumatriptan and donitriptan dose-dependently decreased the carotid blood flow. Interestingly, i.v. administration of the antagonist, SB224289 (5-HT(1B)), but not of BRL15572 (5-HT(1D)), abolished the inhibition by donitriptan.

CONCLUSIONS AND IMPLICATIONS

Our results suggest that the inhibition produced by donitriptan of capsaicin-induced external carotid vasodilatation is mainly mediated by 5-HT(1B), rather than 5-HT(1D), receptors, probably by a central mechanism.

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.

No effect of eletriptan administration during the aura phase of migraine

Migraine aura is a warning sign readily recognized by patients. From the onset of aura it takes 30-60 min before the headache phase starts. Administration of acute medication during aura should provide sufficient time to achieve therapeutic plasma levels, counteracting the headache. To test this hypothesis we evaluated the efficacy of eletriptan 80 mg taken during aura. Patients met International Headache Society diagnostic criteria for migraine with aura, with an attack frequency of at least one per month and with aura occurring in > 50% of recent attacks. Of 123 patients randomized, 87 (71%) were treated with a double-blind, one attack, during the aura phase before headache, dose of either eletriptan 80 mg (n = 43; 74% female; mean age, 40 years), or placebo (n = 44; 82% female; mean age, 40 years). The primary outcome measure was the proportion of patients not developing moderate-to-severe headache within 6 h post-dose. There was no significant difference in the proportion of patients developing moderate-to-severe headache on eletriptan (61%) versus placebo (46%). Eletriptan was well tolerated and did not prolong the aura phase. Typical transient triptan adverse events were observed; most were mild-to-moderate in intensity. This study confirms the findings of two studies showing that triptans are ineffective but safe when given during the migraine aura phrase.

Subcutaneous octreotide in cluster headache: Randomized placebo-controlled double-blind crossover study

Current practical evidence-based acute treatments of cluster headache are limited to subcutaneous and intranasal formulations of sumatriptan, and oxygen. Two small randomized, double-blind trials suggested efficacy of somatostatin in cluster headache. We sought to determine whether octreotide, a somatostatin analog, is effective in the abortive treatment of acute cluster headache. Patients with episodic and chronic cluster headache, as defined by the International Headache Society, were recruited to a double-blind placebo-controlled crossover study. Patients were instructed to treat two attacks of at least moderate pain severity, with at least a 24-hour break, using subcutaneous octreotide microg or matching placebo. The primary end point was the headache response defined as very severe, severe, or moderate pain becomes mild or nil, at 30 minutes. The primary end point was examined using a multilevel analysis approach. A total of 57 patients were recruited of whom 46 provided efficacy data on attacks treated with octreotide and 45 with placebo. The headache response rate with subcutaneous octreotide was 52%, whereas that with placebo was 36%. Modeling the treatment outcome as a binomial where response was determined by treatment, using the patient as the level 2 variable, and considering period effect, sex, and cluster headache type as other variables of interest, we found that the effect of subcutaneous octreotide 100 microg was significantly superior to placebo (p < 0.01). Subcutaneous octreotide 100 microg is effective in the acute treatment of cluster headache when compared with placebo. Nonvasconstrictor treatment of acute cluster headache is possible.

Serotonin inhibits trigeminal nucleus activity evoked by craniovascular stimulation through a 5HT1B/1D receptor: a central action in migraine?

The development of serotonin (5HT1B/1D) agonists as treatments for the acute attack of migraine has resulted in considerable interest in their mechanism of action and, to some extent, renewed interest in the role of serotonin (5-hydroxytryptamine; 5HT) in the disorder. The initial synthesis of this class of compounds was predicated on the clinical observation that intravenous 5HT terminated acute attacks of migraine. In this study the superior sagittal sinus was isolated in the alpha-chloralose (60 mg/kg i.p. and 20 mg/kg i.v. injection supplementary 2 hourly) anesthetized cat. The sinus was stimulated electrically (120V, 250 microsec duration, 0.3 Hz), and neurons of the trigeminocervical complex in the dorsal C2 spinal cord were monitored using electrophysiological methods. After baseline recordings in each animal, 5HT (15 microg/kg/min) was infused for 5 minutes in the presence of either vehicle (group A) or the 5HT1B/1D antagonist GR127935 (100 microg/kg i.v. injection; group B). The baseline probability of cell firing after sagittal sinus stimulation was 0.61 +/- 0.1 at a latency to the fastest peak of 11.1 +/- 0.4 msec. In group A, 5HT infusion alone had a small effect of increasing mean blood pressure (12 +/- 3 mm Hg), which in itself did not alter cell firing. In group A, 5HT alone had an inhibitory effect on evoked trigeminal activity, which developed 15 to 20 minutes after commencement of the infusion. The inhibition of cell firing lasted for 20 minutes, after which the activity returned to baseline. In group B, the combination of 5HT and GR127935 had no effect on trigeminal cell firing, although the small hypertensive effect was still present. These data indicate that 5HT inhibits evoked trigeminal nucleus firing via the 5HT1B/1D receptor at which GR127935 is an antagonist. It is likely that some part of the effect of 5HT in migraine relates to inhibition of trigeminal nucleus activity, just as it is likely that some part of the effect of the triptans is also mediated at this central site and may be complementary to their nonneuronal actions. Moreover, the data highlight the case for describing this class of headache as neurovascular headaches rather than vascular headaches, to recognize the implicit contribution of the trigeminovascular system to their pathophysiology.

Atypical migraine presenting with meningeal signs

A case of atypical or complicated migraine is presented with signs and symptoms of meningeal irritation, projectile emesis NS obtundation, and unresponsiveness. The patient is a 19-year-old diabetic on insulin who had a mild episode of upper respiratory tract symptoms with severe headache and was found unresponsive and brought to the emergency department. After a work-up for meningitis was negative (as well as computerized tomography and magnetic resonance imaging) he recovered totally in 3 days with no residual signs or symptoms and was discharged from the hospital.

Abdominal migraine: a childhood syndrome defined

It has long been recognized that some cases of recurrent abdominal pain in children are related to migraine, but the diagnostic criteria for abdominal migraine have not been defined. We have identified a group of children with recurrent abdominal pain who had a family history of migraine--in over half the cases in a first-degree relative--and who obtained marked relief from their symptoms from specific anti-migraine therapy. These children had a well-defined syndrome comprising episodes of midline abdominal pain of sufficient severity to interfere with normal activities and lasting for prolonged periods, frequently accompanied by pallor, headache, anorexia, nausea, and vomiting. It is proposed that these children have "abdominal migraine".

Mianserin in the prophylaxis of migraine: a double-blind study

Evidence is reviewed indicating that instability in central nervous system handling of 5-hydroxytryptamine may be of primary importance in the pathogenesis of migraine, and that the observed diminution of platelet content and uptake of 5-hydroxytryptamine related to an attack may merely be a reflection of this. The rationale is discussed for selecting mianserin as a potentially effective migraine prophylactic based on: (i) its ability to restore to normal platelet 5-hydroxytryptamine uptake when this is decreased in depression; (ii) its effect on the central nervous system; and particularly (iii) its antiserotonergic activity. A double-blind control trial of mianserin versus placebo in the prophylaxis of migraine is described. There was a significant fall in both frequency and severity of migraine attacks when compared with baseline values in mianserin-treated patients but not in placebo-treated patients. There was no accompanying change on the Beck Depression Inventory. It is concluded that mianserin is an effective migraine prophylactic in some patients. There is no evidence indicating which pharmacological property of mianserin is responsible for this effect.

Calcium-channel blockers in the treatment of migraine

According to classic theory, a migraine attack is initiated by cerebrovascular spasm followed by extracranial vasodilatation. Results of recent studies support this theory and suggest that cerebral blood flow during the initial phase of migraine symptoms is, in fact, decreased and this decrease probably leads to ischemia and hypoxia. Cellular hypoxia, in turn, can cause an increase in the flow of calcium from the extracellular fluid to the intracellular space, resulting in calcium overload and cellular dysfunction. Because calcium-channel blockers selectively inhibit the intracellular influx of calcium ions, investigators have begun evaluating the efficacy of these agents for migraine prophylaxis. Nimodipine, a calcium-channel blocker that exhibits selective effects on cerebral vessels, seems to offer protection against the cerebral ischemia and hypoxia presumed to be operative during migraine attacks. In a double-blind, placebo-controlled study, nimodipine decreased the frequency and duration of migraine attacks by at least half in 69% of patients treated with this agent. Comparable reductions in migraine frequency and duration were attained in 58, 51, 41 and 52% of patients treated with methysergide maleate, pizotifen, clonidine hydrochloride and propranolol, respectively. The piperazine derivative flunarizine also has calcium-channel blocking properties. This agent prevents vasospasm in cerebral arteries and protects against cerebral hypoxia. Results of double-blind studies of migraine prophylaxis with flunarizine demonstrate the beneficial effects of this agent, particularly in younger patients. Flunarizine proved to be superior to pizotifen in decreasing the severity of migraine attacks and comparable to pizotifen in decreasing their frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Cranial computed tomography in pediatric migraine

Two children with migraine showed low-density areas with an irregular enhancement pattern on CT scans of the head after contrast infusion. Angiography was normal in both patients. These abnormalities probably were due to transient blood-brain barrier damage. This knowledge is important when excluding other disorders like vascular malformations.

Brain hypoxia: the turning-point in the genesis of the migraine attack?

The hypothesis postulates that a brief episode of focal cerebral hypoxia occurs in every attack of migraine. Clinical biochemical and technical (EEG and CT scans) evidence is summarized suggesting that cerebral hypoxia is seen as the turning-point in the pathogenesis of the attack. It may be provoked by different mechanisms in different patients; the potential role of decreased oxygen supply and of increased oxygen need are reviewed and excess sympathetic drive is considered a potential key mechanism in a majority of patients. Whether or not focal hypoxia leads to a genuine migraine attack, depends largely upon the quality of the whirlpool of biochemical, vascular and hematological changes that follow the hypoxic episode. These changes are discussed and it is concluded that those which have been reported to occur during migraine attacks could be due to a preceding hypoxic event. Finally, the hypoxia viewpoint is confronted with some popular theories about the pathogenesis of migraine. It is found that the other points of view are compatible with the hypoxia hypothesis.

Domperidone in the prevention of complete classical migraine

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Barrier mechanisms for neurotransmitter monoamines and their precursors at the blood-brain interface

The integrity of the endothelial cell lining of the cerebrovascular bed constitutes a morphological blood-brain barrier mechanism to neurotransmitter monoamines. Circulating monoamines are prevented from entering the brain primarily at the luminal membrane of the endothelial ling. The small percentage of amines that may pass this membrane is deaminated within the endothelial cells and pericytes of brain microvessels (capillaries, venules, and small veins) and, in the case of large parenchymal and pial vessels, in the smooth muscle layers, where O-methylation also takes place. In the choroid plexus a corresponding deamination and O-methylation takes place in the epithelial cells. The presence of these enzymes constitutes a further, enzymatic, blood-brain barrier in the brain vessels for these monoamines. The monoamine precursors L-3,4-dihydroxyphenylalanine (L-dopa) and L-5-hydroxytryptophan readily pass from the luminal endothelial cell membrane but are trapped by another enzymatic barrier mechanism. Within the endothelial cells and pericytes of the microvasculature, these compounds are decarboxylated to their corresponding amines and then immediately deaminated. One clinical implication of these enzymatic barrier mechanisms is the use of decarboxylase and monoamine oxidase inhibitors as adjuncts to L-dopa treatment of Parkinson disease; these substances facilitate the entry of L-dopa into brain and thus increase the amount of dopamine available at receptor sites. A brief hypertensive or hypertonic stimulus can transiently open the blood-brain barrier through an effect on endothelial cell linings. High circulating concentrations of monoamines can also open the morphological barrier, but probably only indirectly by inducing an acute rise in systemic blood pressure. Once the barrier is open, systemically administered monoamines enter the brain parenchyma, where they can induce pronounced changes in cerebral blood flow and metabolism.