From spreading depression to the trigeminovascular system

Optical coherence tomography findings in primary headache disorders: is pain duration a clinical correlate?

OBJECTIVE

Ganglion cell layer thickness (GCLT) may be used as a potential marker for central neural changes. We compared GCLT by using spectral domain optical coherence tomography (SD-OCT) in patients with primary headache disorders and healthy controls. We seek whether there was any difference between the headache groups and whether any clinical parameters correlated to GCLT.

METHODS

Fifty-three primary headache patients, 11 age and sex-matched healthy subjects were included in this cross-sectional study after power analysis. All subjects underwent SD-OCT. The duration of disorder, headache frequency, severity, duration of pain, presence of ocular pain, and accompanying symptoms have been collected.

RESULTS

Mean GCLT of the headache group was 15.7 ± 3.8 µm (mean ± standard deviation), and the control group was 17.5 ± 2.4. The difference was not statistically significant. When we compared the controls, migraine and tension-type headache patients' GCLT values, we found a significant difference (ANOVA, p = 0.001). Migraine patients had thinner GCLT compared to all non-migraine headache patients (p = 0.01). Intraocular pressure values of migraine patients and non-migraine patients were not statistically significantly different (p = 0.13). The only clinical parameter that correlated with GCLT was pain duration (r = -0.43 and p = 0.01). The patients with white matter lesions had thinner GCLT (p = 0.046).

CONCLUSION

Our results suggest that not long-term suffering from pain but migraine pathophysiology itself seems to affect neuroretinal tissue. Pain duration was moderately and inversely correlated to GCLT, meaning that the longer the headache, the thinner the ganglion cell layer is.

Rodent behavior following a dural inflammation model with anti-CGRP migraine medication treatment

Background

Migraine is a widespread and prevalent disease with a complex pathophysiology, of which neuroinflammation and increased pain sensitivity have been suggested to be involved. Various studies have investigated the presence of different inflammatory markers in migraineurs and investigated the role of inflammation in inflammatory models with complete Freund's adjuvant (CFA) or inflammatory soup added to the dura mater.

Objective

The aim of the current study was to examine whether application of CFA to the dura mater would cause behavioral alterations that are migraine relevant. In addition, we investigated the potential mitigating effects of fremanezumab, a CGRP (calcitonin gene-related peptide) specific antibody, following CFA application.

Methods

Male Sprague-Dawley rats were randomly divided into six groups: fresh (n = 7), fresh + carprofen (n = 6), fresh + anti-CGRP (n = 6), sham (n = 7), CFA (n = 16), CFA + anti-CGRP (n = 8). CFA was applied for 15 min on a 3 × 3 mm clearing of the skull exposing the dura mater of male Sprague-Dawley rats. We applied the Light/Dark box and Open Field test, combined with the electronic von Frey test to evaluate outcomes. Finally, we observed CGRP immunoreactivity in the trigeminal ganglion.

Results

No differences were observed in the Light/Dark box test. The Open Field test detected behavior differences, notably that sham rats spend less time in the central zone, reared less and groomed more than fresh + carprofen rats. The other groups were not significantly different compared to sham rats, indicating that activation of the TGVS is present in sham surgery and cannot be exacerbated by CFA. However, for the allodynia, we observed specific periorbital sensitization, not observed in the sham animals. This could not be mitigated by fremanezumab, although it clearly reduced the amount of CGRP positive fibers.

Conclusion

CFA surgically administered to the dura causes periorbital allodynia and increases CGRP positive fibers in the trigeminal ganglion. Fremanezumab does not reduce periorbital allodynia even though it reduces CGRP positive fibers in the TG. Further work is needed to investigate whether CFA administered to the dura could be used as a non-CGRP inflammatory migraine model.

Could Experimental Inflammation Provide Better Understanding of Migraines?

Migraines constitute a common neurological and headache disorder affecting around 15% of the world’s population. In addition to other mechanisms, neurogenic neuroinflammation has been proposed to play a part in migraine chronification, which includes peripheral and central sensitization. There is therefore considerable evidence suggesting that inflammation in the intracranial meninges could be a key element in addition to calcitonin gene-related peptide (CGRP), leading to sensitization of trigeminal meningeal nociceptors in migraines. There are several studies that have utilized this approach, with a strong focus on using inflammatory animal models. Data from these studies show that the inflammatory process involves sensitization of trigeminovascular afferent nerve terminals. Further, by applying a wide range of different pharmacological interventions, insight has been gained on the pathways involved. Importantly, we discuss how animal models should be used with care and that it is important to evaluate outcomes in the light of migraine pathology.

Intracranial nociception

Understanding intracranial nociceptive innervation is essential to understand the pathophysiology of headaches. Our knowledge about human intracranial nociception comes from sparse observations during neurosurgical procedures performed in awake patients, from human anatomical studies and from experimental studies in animals. In this article we review the anatomical and functional organization underlying nociceptive innervation. Intracranial nociception is mainly mediated by the trigeminal system, except in the posterior cranial fossa that is innervated by the first cervical roots. For decades, the dura mater, its vessels and major cerebral blood vessels were considered as the only intracranial pain-sensitive structures. Recent animal and human studies have suggested that smaller brain arteries and potentially pia mater might also be pain sensitive. Nociceptive neurons innervating intracranial blood vessels project via the ophthalmic division (V1) to the trigeminal ganglion and store several neurotransmitters including glutamate, substance P and calcitonin gene-related peptide (CGRP). The trigeminal ganglion, root and brainstem nuclei have a specific topographic and functional somatotopy. Progressive transition between the trigeminal spinal nucleus and the dorsal horn of the cervical spinal cord, and convergence of nociceptive inputs from the face, intracranial structures and the occipital area on the so-called "trigemino-cervical complex" may explain some headache features, relations between facial and occipital pain, and efficacy of occipital nerve stimulation in headache. The specific anatomic organization of the trigeminal system, from the primary-order neuron in the trigeminal ganglion, to the second-order neuron is the trigeminal nuclei, may explain a part of the various characteristics of headaches.

Pannexin-1 Channels as Mediators of Neuroinflammation

Neuroinflammation is a major component of central nervous system (CNS) injuries and neurological diseases, including Alzheimer’s disease, multiple sclerosis, neuropathic pain, and brain trauma. The activation of innate immune cells at the damage site causes the release of pro-inflammatory cytokines and chemokines, which alter the functionality of nearby tissues and might mediate the recruitment of leukocytes to the injury site. If this process persists or is exacerbated, it prevents the adequate resolution of the inflammation, and ultimately enhances secondary damage. Adenosine 5′ triphosphate (ATP) is among the molecules released that trigger an inflammatory response, and it serves as a chemotactic and endogenous danger signal. Extracellular ATP activates multiple purinergic receptors (P2X and P2Y) that have been shown to promote neuroinflammation in a variety of CNS diseases. Recent studies have shown that Pannexin-1 (Panx1) channels are the principal conduits of ATP release from dying cells and innate immune cells in the brain. Herein, we review the emerging evidence that directly implicates Panx-1 channels in the neuroinflammatory response in the CNS.

Intraepidermal Nerve Fiber Density as Measured by Skin Punch Biopsy as a Marker for Small Fiber Neuropathy: Application in Patients with Fibromyalgia

Small fiber neuropathy (SFN) is a type of peripheral neuropathy that occurs from damage to the small A-delta and C nerve fibers that results in the clinical condition known as SFN. This pathology may be the result of metabolic, toxic, immune-mediated, and/or genetic factors. Small fiber symptoms can be variable and inconsistent and therefore require an objective biomarker confirmation. Small fiber dysfunction is not typically captured by diagnostic tests for large-fiber neuropathy (nerve conduction and electromyographic study). Therefore, skin biopsies stained with PGP 9.5 are the universally recommended objective test for SFN, with quantitative sensory tests, autonomic function testing, and corneal confocal imaging as secondary or adjunctive choices. Fibromyalgia (FM) is a heterogenous syndrome that has many symptoms that overlap with those found in SFN. A growing body of research has shown approximately 40-60% of patients carrying a diagnosis of FM have evidence of SFN on skin punch biopsy. There is currently no clearly defined phenotype in FM at this time to suggest whom may or may not have SFN, though research suggests it may correlate with severe cases. The skin punch biopsy provides an objective tool for use in quantifying small fiber pathology in FM. Skin punch biopsy may also be repeated for surveillance of the disease as well as measuring response to treatments. Evaluation of SFN in FM allows for better classification of FM and guidance for patient care as well as validation for their symptoms, leading to better use of resources and outcomes.

The trigeminal system: The meningovascular complex- A review

Supratentorial sensory perception, including pain, is subserved by the trigeminal nerve, in particular, by the branches of its ophthalmic division, which provide an extensive innervation of the dura mater and of the major brain blood vessels. In addition, contrary to previous assumptions, studies on awake patients during surgery have demonstrated that the mechanical stimulation of the pia mater and small cerebral vessels can also produce pain. The trigeminovascular system, located at the interface between the nervous and vascular systems, is therefore perfectly positioned to detect sensory inputs and influence blood flow regulation. Despite the fact that it remains only partially understood, the trigeminovascular system is most probably involved in several pathologies, including very frequent ones such as migraine, or other severe conditions, such as subarachnoid haemorrhage. The incomplete knowledge about the exact roles of the trigeminal system in headache, blood flow regulation, blood barrier permeability and trigemino-cardiac reflex warrants for an increased investigation of the anatomy and physiology of the trigeminal system. This translational review aims at presenting comprehensive information about the dural and brain afferents of the trigeminovascular system, in order to improve the understanding of trigeminal cranial sensory perception and to spark a new field of exploration for headache and other brain diseases.

A Retrospective Analysis of the Impact of Bariatric Surgery on the Management of Chronic Migraine

PURPOSE

To investigate the association of the two most common bariatric surgical procedures, vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB), with sustained remission from chronic migraine.

MATERIALS AND METHODS

Using IBM MarketScan® research database to examine inpatient and pharmacy claims from 2010 through 2017. A cohort of bariatric patients with chronic migraine was created using inclusion and exclusion criteria. Remission was defined as no refill of first-line migraine medication for 180 days after a patients' medication was expected to run out, and recurrence as medication refill after at least 180 days of remission.

RESULTS

Of 1680 patients in our cohort, 931 (55.4%) experienced remission of migraine. Of these, 462 (49.6%) had undergone VSG, while 469 (50.4%) had undergone RYGB. Patients who underwent RYGB had an 11% (RR = 1.11, 95% CI: 1.05, 1.17) increase in likelihood of remission of migraine and a 20% (RR = 0.80, 95% CI: 0.63, 1.04) decrease in likelihood of recurrence of migraine compared to patients who underwent VSG. Older age group, higher number of medications at time of surgery, and female sex were associated with a decreased likelihood of remission.

CONCLUSION

Type of bariatric procedure, age, number of medications at surgery, and sex were the most important predictors of migraine remission after surgery.

Menière's disease caused by CGRP - A new hypothesis explaining etiology and pathophysiology. Redirecting Menière's syndrome to Menière's disease

This paper provides a new hypothetical explanation for the etiopathology and pathophysiology of Menière's Disease (MD), which to date remain unexplained, or incompletely understood. The suggested hypothesis will explain the close connection of MD and Migraine, the coexistence of endolymphatic hydrops (ELH) and Menière attacks and the signs of inflammation detected in the inner ears of MD patients. Although as yet unproven, the explanations provided appear highly plausible and could pave the way for the generation of the first animal model of MD - an invaluable asset for developing new treatment strategies. Furthermore, if proven correct, this hypothesis could redefine and also reset the actual name of Menière's Syndrome to Menière's Disease.

Metabolism plays a central role in the cortical spreading depression: Evidence from a mathematical model

The slow propagating waves of strong depolarization of neural cells characterizing cortical spreading depression, or depolarization, (SD) are known to break cerebral homeostasis and induce significant hemodynamic and electro-metabolic alterations. Mathematical models of cortical spreading depression found in the literature tend to focus on the changes occurring at the electrophysiological level rather than on the ensuing metabolic changes. In this paper, we propose a novel mathematical model which is able to simulate the coupled electrophysiology and metabolism dynamics of SD events, including the swelling of neurons and astrocytes and the concomitant shrinkage of extracellular space. The simulations show that the metabolic coupling leads to spontaneous repetitions of the SD events, which the electrophysiological model alone is not capable to produce. The model predictions, which corroborate experimental findings from the literature, show a strong disruption in metabolism accompanying each wave of spreading depression in the form of a sharp decrease of glucose and oxygen concentrations, with a simultaneous increase in lactate concentration which, in turn, delays the clearing of excess potassium in extracellular space. Our model suggests that the depletion of glucose and oxygen concentration is more pronounced in astrocyte than neuron, in line with the partitioning of the energetic cost of potassium clearing. The model suggests that the repeated SD events are electro-metabolic oscillations that cannot be explained by the electrophysiology alone. The model highlights the crucial role of astrocytes in cleaning the excess potassium flooding extracellular space during a spreading depression event: further, if the ratio of glial/neuron density increases, the frequency of cortical SD events decreases, and the peak potassium concentration in extracellular space is lower than with equal volume fractions.

Are Migraine With and Without Aura Really Different Entities?

Background: Migraine research is booming with the rapidly developing neuroimaging tools. Structural and functional alterations of the migrainous brain were detected with MRI. The outcome of a research study largely depends on the working hypothesis, on the chosen measurement approach and also on the subject selection. Against all evidence from the literature that migraine subtypes are different, most of the studies handle migraine with and without aura as one disease. Methods: Publications from PubMed database were searched for terms of "migraine with aura," "migraine without aura," "interictal," "MRI," "diffusion weighted MRI," "functional MRI," "compared to," "atrophy" alone and in combination. Conclusion: Only a few imaging studies compared the two subforms of the disease, migraine with aura, and without aura, directly. Functional imaging investigations largely agree that there is an increased activity/activation of the brain in migraine with aura as compared to migraine without aura. We propose that this might be the signature of cortical hyperexcitability. However, structural investigations are not equivocal. We propose that variable contribution of parallel, competing mechanisms of maladaptive plasticity and neurodegeneration might be the reason behind the variable results.

Role of Toll-like receptor 4 signaling in mast cell-mediated migraine pain pathway

Degranulation of meningeal mast cells leading to the sensitization of trigeminal vascular afferent processing is believed to be one of the mechanisms underlying the migraine pain pathway. Recent work suggests that Toll-like receptor 4 (TLR4) may be involved in signaling states of central sensitization. Using a murine model of light aversion produced by compound 48/80 (2 mg/kg, intraperitoneal) mast cell degranulation, employed as a surrogate marker for photophobia observed in migraineurs, we examined the role of TLR4 in migraine-like behavior and neuronal activation. Using a two-chambered light/dark box, we found that compound 48/80 administration in male and female C57Bl/6 mice produced light aversion lasting up to 2 h, and that pre-treatment with sumatriptan (1 mg/kg, i.p.) reliably prevented this effect. Genetic deletion and pharmacological blockade of TLR4 with TAK-242 (3 mg/kg, i.p.) reversed the light aversive effects of compound 48/80 in males but not in females. Assessing the downstream signaling pathway in mutant mice, we found that the TLR4-mediated, light aversion was dependent upon myeloid differentiation primary response gene 88 but not Toll-interleukin-1 receptor domain-containing adapter-inducing interferon-β signaling. In separate groups, male mice sacrificed at 10 min following compound 48/80 revealed a significant increase in the incidence of evoked p-extracellular signal–regulated kinases (+) neurons in the nucleus caudalis of wild type but not Tlr4−/− mice or in mice pre-treated with sumatriptan. This study thus provides the first evidence for involvement of TLR4 signaling through MyD88 in initiating and maintaining migraine-like behavior and nucleus caudalis neuronal activation in the mouse.

Positional Patterns Among the Auriculotemporal Nerve, Superficial Temporal Artery, and Superficial Temporal Vein for use in Decompression Treatments for Migraine

This study aimed to clarify intersection patterns and points among the superficial temporal artery (STA), superficial temporal vein (STV), and auriculotemporal nerve (ATN) based on surface anatomical landmarks to provide useful anatomical information for surgical decompression treatments of migraine headaches in Asians. Thirty-eight hemifaces were dissected. The positional patterns among the ATN, STA, and STV were divided into three morphological types. In type I, the ATN ran toward the temporal region and superficially intersected the STA and STV (n = 32, 84.2%). In type II, the ATN ran toward the temporal region and deeply intersected the STA and STV (n = 4, 10.5%). In type III, the ATN ran toward the temporal region and deeply intersected the STV alone (n = 2, 5.3%). The intersection points of types II and III were 10.3 ± 5.6 mm (mean ± SD) and 10.4 ± 6.1 mm anterior and 42.1 ± 21.6 mm and 41.4 ± 18.7 mm superior to the tragus, respectively. The ATN superficially intersected the STA and STV in all the Korean cadaver, while the ATN deeply intersected the STA and STV in 15% of the Thai cadavers. The pattern of the ATN deeply intersecting the STA and STV was less common in present Asian populations than in previously-reported Caucasian populations, implying that migraine headaches (resulting from the STA and STV compressing the ATN) are less common in Asians.

Video head impulse test (vHIT) in migraine dizziness

BACKGROUND AND OBJECTIVE

Migraine is an extremely prevalent primary headache disorder that frequently associates parallel symptoms such as dizziness, tinnitus and hearing loss. Our aim is to investigate differences in video head impulse (vHIT) results with patients suffering from vestibular migraine (VM) and healthy people, taking into consideration mean values of vestibule ocular reflex (VOR) gain, occurrence of the compensatory saccades latency and amplitude. According to the results, determine the usefulness of vHIT in vestibular migraine diagnostics.

METHODS

A total number of 120 subjects were enrolled in the study, 80 of them were vestibular migraine patients (VM), while the other 40 were a control group of age matched healthy subjects. History was taking during the evaluation; videonystagmography and the video head impulse test were done.

RESULTS

The rate of saccades is much more higher in the VM group compared to the healthy subjects group, only 7.5% of the VM group showed a low VOR gain with compensatory saccades denoting a vestibular deficit.

CONCLUSION

The refixation saccades are an important sign that could underlie different vestibular problems. vHIT result can contribute to the completion of full mosaic of vestibular migraine diagnostics.

Effect of serotonin depletion on cortical spreading depression evoked cerebrovascular changes

Abstract Background: The cortical spreading depression (CSD) is a phenomenon associated with several pathological conditions including migraine. It can induce alterations in both neural and vascular compartments. Serotonin (5-HT) depletion is known as a condition involved in migraine pathophysiology. The hyper-excitability of the cortical neurons to the CSD activation in the low 5-HT state has been previously reported. However, the cerebrovascular responses to CSD activation in this condition have never been studied yet. Objectives: Determine the effect of 5-HT depletion on the cerebrovascular responses to CSD activation. Methods: Wistar rats (weighing 250-300 grams) were divided into three groups: control, CSD, and low 5-HT with CSD group (five rats per group). To induce the low 5-HT state, the para-chlorophenylalanine was injected intraperitoneally into the rats three days before the experiment. CSD was induced by the application of solid KCl (3 mg) on the parietal cortex. NaCl instead of KCl was applied to the control group. Cerebral cortical blood flow was monitored using Laser Doppler flowmetry. The ultrastructure of cerebral microvessels was examined using electron microscopy to determine the cerebral microcirculatory responses to CSD. Results: Depletion of serotonin induced a significant increase in the peak amplitude of CSD-evoked cerebral hyperaemia. This condition also enhanced the development of CSD-induced endothelial pinocytosis and microvillus formation in cerebrocortical microvessels. Conclusion: 5-HT was an important neurotransmitter involved in the control of cerebrovascular responses to CSD activation. The hypersensitivity of the cerebrovascular responses observed in the 5-HT depleted state may explain the relationship between headache and 5-HT depletion.

Neurogenic inflammation and its role in migraine

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

The CGRP receptor antagonist BIBN4096 inhibits prolonged meningeal afferent activation evoked by brief local K+ stimulation but not cortical spreading depression-induced afferent sensitization

Calcitonin gene-related peptide mediates K⁺-evoked delayed and prolonged activation of cranial meningeal afferents but does not contribute to their enhanced responsiveness following cortical spreading depression.

Introduction:

Cortical spreading depression (CSD) is believed to promote migraine headache by enhancing the activity and mechanosensitivity of trigeminal intracranial meningeal afferents. One putative mechanism underlying this afferent response involves an acute excitation of meningeal afferents by cortical efflux of K⁺ and the ensuing antidromic release of proinflammatory sensory neuropeptides, such as calcitonin gene-related peptide (CGRP).

Objectives:

We sought to investigate whether (1) a brief meningeal K⁺ stimulus leads to CGRP-dependent enhancement of meningeal afferent responses and (2) CSD-induced meningeal afferent activation and sensitization involve CGRP receptor signaling.

Methods:

Extracellular single-unit recording were used to record the activity of meningeal afferents in anesthetized male rats. Stimulations included a brief meningeal application of K⁺ or induction of CSD in the frontal cortex using pinprick. Cortical spreading depression was documented by recording changes in cerebral blood flow using laser Doppler flowmetery. Calcitonin gene-related peptide receptor activity was inhibited with BIBN4096 (333 μM, i.v.).

Results:

Meningeal K⁺ stimulation acutely activated 86% of the afferents tested and also promoted in ∼65% of the afferents a 3-fold increase in ongoing activity, which was delayed by 23.3 ± 4.1 minutes and lasted for 22.2 ± 5.6 minutes. K⁺ stimulation did not promote mechanical sensitization. Pretreatment with BIBN4096 suppressed the K⁺-induced delayed afferent activation, reduced CSD-evoked cortical hyperemia, but had no effect on the enhanced activation or mechanical sensitization of meningeal afferents following CSD.

Conclusion:

While CGRP-mediated activation of meningeal afferents evoked by cortical efflux of K⁺ could promote headache, acute activation of CGRP receptors may not play a key role in mediating CSD-evoked headache.

Alice in Wonderland Syndrome: A Historical and Medical Review

Alice in Wonderland syndrome is a disorienting neurological condition that affects human perception to the senses of vision, hearing, touch, sensation, and the phenomenon of time. Individuals affected with Alice in Wonderland syndrome can experience alterations in their perception of the size of objects or their own body parts, known as metamorphopsias. It is known to occur in conditions including migraine, epilepsy, and certain intoxicants and infectious diseases. The name refers to Lewis Carrol's well-known children's book Alice's Adventures in Wonderland, in which the title character experiences alterations of sensation in which she felt that her body had grown too tall or too small, or parts of her body were changing shape, size, or relationship to the rest of her body. The syndrome was described in 1952 by Caro Lippman, and given its name in 1955 by John Todd. The metamorphopsias characteristic of this condition are also sometimes referred to as Lilliputian hallucinations, a reference to the fictional island of Lilliput in the novel Gulliver's Travels, written by Jonathan Swift in 1726. As such, many literary and medical publications have roots in the description of this syndrome. The purpose of this review is to summarize the literary and historical significance of Alice in Wonderland syndrome, as well as to provide the reader with a medical overview of the condition.

PI3K/AKT signaling pathway activation in a rat model of migraine

The present study aimed to investigate phosphatidylinositol 4,5-bisphosphate 3‑kinase (PI3K)/protein kinase B (AKT) signaling pathway activation in a rat model of migraine. A total of 60 male Sprague‑Dawley rats were randomly divided into three groups: Blank control; suspension control; and migraine model. The model group was subcutaneously injected with a glyceryl trinitrate suspension, using an optimized Tassorelli method to establish a rat model of migraine. The activation status of the PI3K/AKT signaling pathway was assessed via measurement of the phosphorylated (p)‑AKT level. The level of serum 5‑hydroxytryptamine was detected using an ELISA. The mRNA and protein expression levels of PI3K and AKT, and protein levels of p‑AKT were detected by reverse transcription quantitative polymerase chain reaction and western blot analysis. Expression of the PI3K gene was significantly increased (P<0.01) 6‑24 h following the glyceryl trinitrate injection. There was no significant difference in the expression of AKT between any of the groups at any time. Expression of p‑AKT (S473) was significantly increased in the migraine model group (P<0.01) compared with the controls groups. Immunohistochemical analysis indicated that phosphatase and tensin homolog (PTEN) continuously decreased in the migraine model group during 1‑12 h, however this was only significant in the 12 h group. Levels of PTEN had increased again by 24 h. Glycogen synthase kinase (GSK)‑3β expression exhibited a similar expression pattern to PTEN. The results indicated that the PI3K/AKT signal pathway may be activated in the brain tissue of the rat migraine models. The inhibition of PTEN, which is an upstream modulator of the PI3K/AKT signaling pathway, may enhance the activation of phosphatidylinositol‑3,4,5‑triphosphate, thus inhibiting the expression of GSK-3β.

Increased migraine risk in osteoporosis patients: a nationwide population-based study

BACKGROUND

Osteoporosis and migraine are both important public health problems and may have overlapping pathophysiological mechanisms. The aim of this study was to use a Taiwanese population-based dataset to assess migraine risk in osteoporosis patients.

METHODS

The Taiwan National Health Insurance Research Database was used to analyse data for 40,672 patients aged ≥20 years who had been diagnosed with osteoporosis during 1996-2010. An additional 40,672 age-matched patients without osteoporosis were randomly selected as the non-osteoporosis group. The relationship between osteoporosis and migraine risk was estimated using Cox proportional hazard regression models.

RESULTS

During the follow-up period, 1110 patients with osteoporosis and 750 patients without osteoporosis developed migraine. After controlling for covariates, the overall incidence of migraine was 1.37-fold higher in the osteoporosis group than in the non-osteoporosis group (3.72 vs. 1.24 per 1000 person-years, respectively). Migraine risk factors included high Charlson Comorbidity Index score, female gender, hypertension, depression, asthma, allergic rhinitis, obesity, and tobacco use disorder.

CONCLUSIONS

Our results indicate that patients with a history of osteoporosis had a higher risk of migraine.

The Influence of Na(+), K(+)-ATPase on Glutamate Signaling in Neurodegenerative Diseases and Senescence

Decreased Na(+), K(+)-ATPase (NKA) activity causes energy deficiency, which is commonly observed in neurodegenerative diseases. The NKA is constituted of three subunits: α, β, and γ, with four distinct isoforms of the catalytic α subunit (α1-4). Genetic mutations in the ATP1A2 gene and ATP1A3 gene, encoding the α2 and α3 subunit isoforms, respectively can cause distinct neurological disorders, concurrent to impaired NKA activity. Within the central nervous system (CNS), the α2 isoform is expressed mostly in glial cells and the α3 isoform is neuron-specific. Mutations in ATP1A2 gene can result in familial hemiplegic migraine (FHM2), while mutations in the ATP1A3 gene can cause Rapid-onset dystonia-Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC), as well as the cerebellar ataxia, areflexia, pescavus, optic atrophy and sensorineural hearing loss (CAPOS) syndrome. Data indicates that the central glutamatergic system is affected by mutations in the α2 isoform, however further investigations are required to establish a connection to mutations in the α3 isoform, especially given the diagnostic confusion and overlap with glutamate transporter disease. The age-related decline in brain α2∕3 activity may arise from changes in the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase (PKG) pathway. Glutamate, through nitric oxide synthase (NOS), cGMP and PKG, stimulates brain α2∕3 activity, with the glutamatergic N-methyl-D-aspartate (NMDA) receptor cascade able to drive an adaptive, neuroprotective response to inflammatory and challenging stimuli, including amyloid-β. Here we review the NKA, both as an ion pump as well as a receptor that interacts with NMDA, including the role of NKA subunits mutations. Failure of the NKA-associated adaptive response mechanisms may render neurons more susceptible to degeneration over the course of aging.

Migraine in the era of precision medicine

Migraine is a common neurovascular disorder in the neurologic clinics whose mechanisms have been explored for several years. The aura has been considered to be attributed to cortical spreading depression (CSD) and dysfunction of the trigeminovascular system is the key factor that has been considered in the pathogenesis of migraine pain. Moreover, three genes (CACNA1A, ATP1A2, and SCN1A) have come from studies performed in individuals with familial hemiplegic migraine (FHM), a monogenic form of migraine with aura. Therapies targeting on the neuropeptids and genes may be helpful in the precision medicine of migraineurs. 5-hydroxytryptamine (5-HT) receptor agonists and calcitonin gene-related peptide (CGRP) receptor antagonists have demonstrated efficacy in the acute specific treatment of migraine attacks. Therefore, ongoing and future efforts to find new vulnerabilities of migraine, unravel the complexity of drug therapy, and perform biomarker-driven clinical trials are necessary to improve outcomes for patients with migraine.

Is Retinal Nerve Fiber Layer Thickness Change Related to Headache Lateralization in Migraine?

PURPOSE

To evaluate retinal nerve fiber layer (RNFL) thickness in migraine patients with unilateral headache.

METHODS

A total of 58 patients diagnosed with migraine headache consistently occurring on the same side and 58 age- and sex-matched healthy subjects were evaluated in this cross-sectional study. RNFL thickness was measured using spectral-domain optical coherence tomography, and the side with the headache was compared with the contralateral side as well as with the results of healthy subjects.

RESULTS

The mean patient age was 33.05 ± 8.83 years, and that of the healthy subjects was 31.44 ± 8.64 years (p = 0.32). The mean duration of disease was 10.29 ± 9.03 years. The average and nasal RNFL thicknesses were significantly thinner on the side of headache and on the contralateral side compared to control eyes (p < 0.05, for all). Thinning was higher on the side of the headache compared to the contralateral side; however, this difference was not statistically significant.

CONCLUSIONS

The RNFL thicknesses were thinner on the side of the headache compared to the contralateral side in the migraine patients with unilateral headache, but this difference was not statistically significant.

Case-control study of ADARB1 and ADARB2 gene variants in migraine

Background

Migraine causes crippling attacks of severe head pain along with associated nausea, vomiting, photophobia and/or phonophobia. The aim of this study was to investigate single nucleotide polymorphisms (SNPs) in the adenosine deaminase, RNA-specific, B1 (ADARB1) and adenosine deaminase, RNA specific, B2 (ADARB2) genes in an Australian case–control Caucasian population for association with migraine. Both candidate genes are highly expressed in the central nervous system and fit criteria for migraine neuropathology. SNPs in the ADARB2 gene were previously found to be positively associated with migraine in a pedigree-based genome wide association study using the genetic isolate of Norfolk Island, Australia. The ADARB1 gene was also chosen for investigation due to its important function in editing neurotransmitter receptor transcripts.

Methods

Four SNPs in ADARB1 and nine in ADARB2 were selected by inspecting blocks of linkage disequilibrium in Haploview for genotyping using either TaqMan or Sequenom assays. These SNPs were genotyped in two-hundred and ninety one patients who satisfied the International Classification of Headache Disorders-II 2004 diagnostic criteria for migraine, and three-hundred and fourteen controls, and PLINK was used for association testing.

Results

Chi-square analysis found no significant association between any of the SNPs tested in the ADARB1 and ADARB2 genes in this study and the occurrence of migraine.

Conclusions

In contrast to findings that SNPs in the ADARB2 gene were positively associated with migraine in the Norfolk Island population, we find no evidence to support the involvement of RNA editing genes in migraine susceptibility in an Australian Caucasian population.

The visual system in migraine: from the bench side to the office

BACKGROUND

Throughout history, migraine-associated visual symptoms have puzzled patients, doctors, and neuroscientists. The visual aspects of migraine extend far beyond the aura phenomena, and have several clinical implications.

METHODS

A narrative review was conducted, beginning with migraine mechanisms, then followed by pertinent aspects of the anatomy of visual pathways, clinical features, implications of the visual system on therapy, migraine on visually impaired populations, treatment of visual auras and ocular (retinal) migraine, effect of prophylactic migraine treatments on visual aura, visual symptoms induced by anti-migraine or anti-headache drugs, and differential diagnosis.

RESULTS

A comprehensive narrative review from both basic and clinical standpoints on the visual aspects of migraine was attained; however, the results were biased to provide any useful information for the clinician.

CONCLUSION

This paper achieved its goals of addressing and condensing information on the pathophysiology of the visual aspects of migraine and its clinical aspects, especially with regards to therapy, making it useful not only for those unfamiliar to the theme but to experienced physicians as well.

Gene expression microarray analysis of the spinal trigeminal nucleus in a rat model of migraine with aura

Cortical spreading depression can trigger migraine with aura and activate the trigeminal vascular system. To examine gene expression profiles in the spinal trigeminal nucleus in rats following cortical spreading depression-induced migraine with aura, a rat model was established by injection of 1 M potassium chloride, which induced cortical spreading depression. DNA microarray analysis revealed that, compared with the control group, the cortical spreading depression group showed seven upregulated genes–myosin heavy chain 1/2, myosin light chain 1, myosin light chain (phosphorylatable, fast skeletal muscle), actin alpha 1, homeobox B8, carbonic anhydrase 3 and an unknown gene. Two genes were downregulated–RGD1563441 and an unknown gene. Real-time quantitative reverse transcription-PCR and bioinformatics analysis indicated that these genes are involved in motility, cell migration, CO₂/nitric oxide homeostasis and signal transduction.

Poloxamer-188 and citicoline provide neuronal membrane integrity and protect membrane stability in cortical spreading depression

Under pathological conditions such as brain trauma, subarachnoid hemorrhage and stroke, cortical spreading depression (CSD) or peri-infarct depolarizations contribute to brain damage in animal models of neurological disorders as well as in human neurological diseases. CSD causes transient megachannel opening on the neuronal membrane, which may compromise neuronal survival under pathological conditions. Poloxamer-188 (P-188) and citicoline are neuroprotectants with membrane sealing properties. The aim of this study is to investigate the effect of P-188 and citicoline on the neuronal megachannel opening induced by CSD in the mouse brain. We have monitored megachannel opening with propidium iodide, a membrane impermeable fluorescent dye and, demonstrate that P-188 and citicoline strikingly decreased CSD-induced neuronal PI influx in cortex and hippocampal dentate gyrus. Therefore, these agents may be providing neuroprotection by blocking megachannel opening, which may be related to their membrane sealing action and warrant further investigation for treatment of traumatic brain injury and ischemic stroke.

Pregabalin alleviates the nitroglycerin-induced hyperalgesia in rats

The association between the clinical use of nitroglycerin (NTG) and migraine suggests NTG as an animal model trigger for migraine. NTG-induced hyperalgesia in rats has been extensively used as a migraine model for pre-clinical research. Pregabalin is an anti-epileptic drug and may play a role in the preventive treatment of migraine; however, the mechanism of this action remains to be clarified. Herein, we performed the present study to investigate the effect of pregabalin on the NTG-induced hyperalgesia in rats. Sixty male Sprague-Dawley rats were divided equally into six groups. Thirty minutes before NTG injection, the rats were pretreated with pregabalin. von Frey hair testing was employed to evaluate tactile sensitivity. Enzyme-linked immunosorbent assay was used to analyze plasma calcitonin gene-related peptide (CGRP) levels in the jugular vein. Immunohistochemistry was applied to detect c-Fos-immunoreactive neurons and western blot was performed to detect c-Fos protein expression in trigeminal nucleus caudalis (TNC). We found that pregabalin pretreatment alleviated the NTG-induced hyperalgesia. Moreover, pregabalin suppressed peripheral CGRP release, c-Fos-immunoreactive neurons and the protein expression of c-Fos in TNC as well. These data suggest that pregabalin could alleviate the NTG-induced hyperalgesia. Further studies are required to determine the mechanisms of action for this effect.

Headache during a cluster of benign paroxysmal positional vertigo attacks

OBJECTIVE

In view of patients' recurrent complaints, we were interested in investigating the frequency and headache characteristics in patients during a benign paroxysmal positional vertigo (BPPV) cluster.

METHODS

Patients with BPPV treated at an outpatient dizziness clinic were interviewed about the presence of headache; its quality, localization, severity, time course, and aggravating and alleviating factors; and headache-related disability during their present vertigo cluster.

RESULTS

Among 152 patients with BPPV, 53 (34.8%) reported headache associated with vertigo. According to The International Classification of Headache Disorders, 8 (15%) patients could be classified as migraine without aura (1.1), 14 (26%) were classified as infrequent episodic tension-type headache associated with pericranial tenderness (2.1.1), 23 (43%) were classified as infrequent episodic tension-type headache without pericranial tenderness (2.1.2), 6 (11%) had cervicogenic headache (11.2.1), and in 2 (4%) patients, the headache could not be specified (14.2). Fifty-two age-matched BPPV patients without headache did not differ in history of headaches, BPPV history, or background diseases. The distribution of canal involvement and number of treatment maneuvers was also similar in both groups.

CONCLUSION

Headache is frequent in BPPV. The most common is tension-type headache, followed by migraine and cervicogenic headache. Head pain seems to be an independently associated epiphenomenon of BPPV that can worsen patients' distress.

Modelling headache and migraine and its pharmacological manipulation

Similarities between laboratory animals and humans in anatomy and physiology of the cephalic nociceptive pathways have allowed scientists to create successful models that have significantly contributed to our understanding of headache. They have also been instrumental in the development of novel anti-migraine drugs different from classical pain killers. Nevertheless, modelling the mechanisms underlying primary headache disorders like migraine has been challenging due to limitations in testing the postulated hypotheses in humans. Recent developments in imaging techniques have begun to fill this translational gap. The unambiguous demonstration of cortical spreading depolarization (CSD) during migraine aura in patients has reawakened interest in studying CSD in animals as a noxious brain event that can activate the trigeminovascular system. CSD-based models, including transgenics and optogenetics, may more realistically simulate pain generation in migraine, which is thought to originate within the brain. The realization that behavioural correlates of headache and migrainous symptoms like photophobia can be assessed quantitatively in laboratory animals, has created an opportunity to directly study the headache in intact animals without the confounding effects of anaesthetics. Headache and migraine-like episodes induced by administration of glyceryltrinitrate and CGRP to humans and parallel behavioural and biological changes observed in rodents create interesting possibilities for translational research. Not unexpectedly, species differences and model-specific observations have also led to controversies as well as disappointments in clinical trials, which, in return, has helped us improve the models and advance our understanding of headache. Here, we review commonly used headache and migraine models with an emphasis on recent developments.

Reactive oxygen species induce procalcitonin expression in trigeminal ganglia glia

OBJECTIVE

To examine calcitonin gene-related peptide (CGRP) gene expression under inflammatory conditions using trigeminal ganglia organ cultures as an experimental system. These cultures have increased proinflammatory signaling that may mimic neurogenic inflammation in the migraine state.

BACKGROUND

The trigeminal nerve sends peripheral pain signals to the central nervous system during migraine. Understanding the dynamic processes that occur within the trigeminal nerve and ganglion may provide insights into events that contribute to migraine pain. A neuropeptide of particular interest is CGRP, which can be elevated and play a causal role in migraine. However, most studies have overlooked a second splice product of the Calca gene that encodes calcitonin (CT), a peptide hormone involved in calcium homeostasis. Importantly, a precursor form of CT called procalcitonin (proCT) can act as a partial agonist at the CGRP receptor and elevated proCT has recently been reported during migraine.

METHODS

We used a trigeminal ganglion whole organ explant model, which has previously been demonstrated to induce pro-inflammatory agents in vitro. Quantitative polymerase chain reaction and immunohistochemistry were used to evaluate changes in messenger ribonucleic acid (mRNA) and protein levels of CGRP and proCT.

RESULTS

Whole mouse trigeminal ganglia cultured for 24 hours showed a 10-fold increase in CT mRNA, with no change in CGRP mRNA. A similar effect was observed in ganglia from adult rats. ProCT immunoreactivity was localized in glial cells. Cutting the tissue blunted the increase in CT, suggesting that induction required the close environment of the intact ganglia. Consistent with this prediction, there were increased reactive oxygen species in the ganglia, and the elevated CT mRNA was reduced by antioxidant treatment. Surprisingly, reactive oxygen species were increased in neurons, not glia.

CONCLUSIONS

These results demonstrate that reactive oxygen species can activate proCT expression from the CGRP gene in trigeminal glia by a paracrine regulatory mechanism. We propose that this glial recruitment pathway may occur following cortical spreading depression and neurogenic inflammation to increase CGRP nociceptive actions in migraine.

Genetic analysis of GRIA2 and GRIA4 genes in migraine

BACKGROUND

Migraine is a brain disorder affecting ∼12% of the Caucasian population. Genes involved in neurological, vascular, and hormonal pathways have all been implicated in predisposing individuals to developing migraine. The migraineur presents with disabling head pain and varying symptoms of nausea, emesis, photophobia, phonophobia, and occasionally visual sensory disturbances. Biochemical and genetic studies have demonstrated dysfunction of neurotransmitters: serotonin, dopamine, and glutamate in migraine susceptibility. Glutamate mediates the transmission of excitatory signals in the mammalian central nervous system that affect normal brain function including cognition, memory and learning. The aim of this study was to investigate polymorphisms in the GRIA2 and GRIA4 genes, which encode subunits of the ionotropic AMPA receptor for association in an Australian Caucasian population.

METHODS

Genotypes for each polymorphism were determined using high resolution melt analysis and the RFLP method.

RESULTS

Statistical analysis showed no association between migraine and the GRIA2 and GRIA4 polymorphisms investigated.

CONCLUSIONS

Although the results of this study showed no significant association between the tested GRIA gene variants and migraine in our Australian Caucasian population further investigation of other components of the glutamatergic system may help to elucidate if there is a relationship between glutamatergic dysfunction and migraine.

Migraine strikes as neuronal excitability reaches a tipping point

Self-propagating waves of cerebral neuronal firing, known as spreading depolarisations, are believed to be at the roots of migraine attacks. We propose that the start of spreading depolarisations corresponds to a critical transition that occurs when dynamic brain networks approach a tipping point. We show that this hypothesis is consistent with current pathogenetic insights and observed dynamics. Our view implies that migraine strikes when modulating factors further raise the neuronal excitability in genetically predisposed subjects to a level where even minor perturbations can trigger spreading depolarisations. A corollary is that recently discovered generic early warning indicators for critical transitions may be used to predict the onset of migraine attacks even before patients are clinically aware. This opens up new avenues for dissecting the mechanisms for the onset of migraine attacks and for identifying novel prophylactic treatment targets for the prevention of attacks.

Studies on the pathophysiology and genetic basis of migraine

Migraine is a neurological disorder that affects the central nervous system causing painful attacks of headache. A genetic vulnerability and exposure to environmental triggers can influence the migraine phenotype. Migraine interferes in many facets of people's daily life including employment commitments and their ability to look after their families resulting in a reduced quality of life. Identification of the biological processes that underlie this relatively common affliction has been difficult because migraine does not have any clearly identifiable pathology or structural lesion detectable by current medical technology. Theories to explain the symptoms of migraine have focused on the physiological mechanisms involved in the various phases of headache and include the vascular and neurogenic theories. In relation to migraine pathophysiology the trigeminovascular system and cortical spreading depression have also been implicated with supporting evidence from imaging studies and animal models. The objective of current research is to better understand the pathways and mechanisms involved in causing pain and headache to be able to target interventions. The genetic component of migraine has been teased apart using linkage studies and both candidate gene and genome-wide association studies, in family and case-control cohorts. Genomic regions that increase individual risk to migraine have been identified in neurological, vascular and hormonal pathways. This review discusses knowledge of the pathophysiology and genetic basis of migraine with the latest scientific evidence from genetic studies.

A cyclic pain: the pathophysiology and treatment of menstrual migraine

Catamenial migraine is a headache disorder occurring in reproductive-aged women relevant to menstrual cycles. Catamenial migraine is defined as attacks of migraine that occurs regularly in at least 2 of 3 consecutive menstrual cycles and occurs exclusively on day 1 to 2 of menstruation, but may range from 2 days before (defined as -2) to 3 days after (defined as +3 with the first day of menstruation as day +1). There are 2 subtypes: the pure menstrual migraine and menstrually related migraine. In pure menstrual migraine, there are no aura and no migraine occurring during any other time of the menstrual cycle. In contrast, menstrually related migraine also occurs in 2 of 3 consecutive menstrual cycles, mostly on days 1 and 2 of menstruation, but it may occur outside the menstrual cycle. Catamenial migraine significantly interferes with the quality of life and causes functional disability in most sufferers. The fluctuation of estrogen levels is believed to play a role in the pathogenesis of catamenial migraine. In this review, we discuss estrogen and its direct and indirect pathophysiologic roles in menstrual-related migraine headaches and the available treatment for women.

TARGET AUDIENCE

Obstetricians and gynecologists, family physicians.

LEARNING OBJECTIVES

After completing this CME activity, physicians should be better able to discuss the pathophysiology of catamenial migraine, identify the risk factors for catamenial migraine among women, and list the prophylactic and abortive treatments for migraines.

Spreading depression triggers headache by activating neuronal Panx1 channels

The initial phase in the development of a migraine is still poorly understood. Here, we describe a previously unknown signaling pathway between stressed neurons and trigeminal afferents during cortical spreading depression (CSD), the putative cause of migraine aura and headache. CSD caused neuronal Pannexin1 (Panx1) megachannel opening and caspase-1 activation followed by high-mobility group box 1 (HMGB1) release from neurons and nuclear factor κB activation in astrocytes. Suppression of this cascade abolished CSD-induced trigeminovascular activation, dural mast cell degranulation, and headache. CSD-induced neuronal megachannel opening may promote sustained activation of trigeminal afferents via parenchymal inflammatory cascades reaching glia limitans. This pathway may function to alarm an organism with headache when neurons are stressed.

The Alice in Wonderland syndrome

The Alice in Wonderland syndrome is a term applied to altered bizarre perceptions of size and shapes of a patient's body and illusions of changes in the forms, dimensions, and motions of objects that a patient with this syndrome encounters. These metamorphopsias arise during complex partial seizures, migraine headaches, infections, and intoxications. The illusions and hallucinations resemble the strange phenomena that Alice experienced in Lewis Carroll's Alice's Adventures in Wonderland. Charles Lutwidge Dodgson, whose nom de plume was Lewis Carroll, experienced metamorphopsias. He described them in the story that he wrote for Alice Liddell and her two sisters after he spun a tale about a long and strange dream that the fictional Alice had on a warm summer day. The author of this chapter suggests that Dodgson suffered from migraine headaches and used these experiences to weave an amusing tale for Alice Liddell. The chapter also discusses the neurology of mercury poisoning affecting the behavior of Mad Hatter character. The author suggests that the ever-somnolent Dormouse suffered from excessive daytime sleepiness due to obstructive sleep apnea.

Paradoxical air microembolism induces cerebral bioelectrical abnormalities and occasionally headache in patent foramen ovale patients with migraine

BACKGROUND

Although controversial, paradoxical embolism via patent foramen ovale (PFO) may account for some of the migraine attacks in a subset of migraine with aura (MA) patients. Induction of MA attacks with air bubble injection during transcranial Doppler ultrasound in MA patients with PFO supports this view. It is likely that cerebral embolism in patients with right-to-left shunt induces bioelectrical abnormalities to initiate MA under some conditions.

METHODS AND RESULTS

We investigated changes in cerebral bioelectrical activity after intravenous microbubble injection in 10 MA patients with large PFO and right-to-left cardiac shunt. Eight PFO patients without migraine but with large right-to-left shunt and 12 MA patients without PFO served as controls. Four MA patients with PFO were reexamined with sham injections of saline without microbubbles. Bioelectrical activity was evaluated using spectral electroencephalography and, passage of microbubbles through cerebral arteries was monitored with transcranial Doppler ultrasound. Microbubble embolism caused significant electroencephalographic power increase in MA+PFO patients but not in control groups including the sham-injected MA+PFO patients. Headache developed in 2 MA with PFO patients after microbubble injection.

CONCLUSIONS

These findings demonstrate that air microembolism through large PFOs may cause cerebral bioelectrical disturbances and, occasionally, headache in MA patients, which may reflect an increased reactivity of their brain to transient subclinical hypoxia-ischemia, and suggest that paradoxical embolism is not a common cause of migraine but may induce headache in the presence of a large PFO and facilitating conditions.

Structural and functional neuroimaging in migraine: insights from 3 decades of research

Modern imaging methods provide unprecedented insights into brain structure, perfusion, metabolism, and neurochemistry, both during and between migraine attacks. Neuroimaging investigations conducted in recent decades bring us closer to uncovering migraine as a multifaceted, primarily central nervous system disorder. Three main categories of structural and functional brain changes are described in this review, corresponding to the migrainous aura, ictal headache, and interictal states. These changes greatly advance our understanding of multiple pathophysiologic underpinnings of migraine, from central "migraine generating" loci, to cortical spreading depression, intimate mechanisms underlying activation of neuronal pain pathways in vulnerable patients, central sensitization, and chronification. Structural imaging begins to explain the complex connections between migraine and cerebral vascular events, white matter lesions, grey matter density alterations, iron deposition, and microstructural brain damage. Selected structural and functional alterations of brain structures, as identified with imaging methods, may represent the foundation of new diagnostic strategies and serve as markers of therapeutic efficacy.

Migraine diagnosis and pathophysiology

PURPOSE OF REVIEW

This article describes current knowledge regarding headache, especially migraine, and includes information on genetics, anatomy, pathophysiology, and pharmacology in order to demonstrate their relevance to clinical phenomenology.

RECENT FINDINGS

Animal models show that drugs effective in migraine prevention may work by raising the threshold for initiating cortical spreading depression and may also attenuate the response to simulation.

SUMMARY

Great advances have been made in diagnosing and understanding migraine over the past several decades. Tools such as the International Classification of Headache Disorders assist in making diagnoses. Although blood vessel changes do occur in migraine, they are not timelocked to the occurrence of head pain. Cortical spreading depression is at least one trigger for the events that occur in migraine. Migraine may be due to the interplay of host susceptibility and various triggers. Nitric oxide and calcitonin gene-related peptide are important mediators, and estrogen seems to "ramp up" the system.

Migraine changes the brain: neuroimaging makes its mark

PURPOSE OF REVIEW

This review summarizes key findings of the current literature on functional neuroimaging in migraine and describes how these studies have changed our view of the disorder.

RECENT FINDINGS

Recent studies have started not only to investigate the global cerebral activation pattern during migraine attacks, but to address specific aspects of migraine attacks such as photophobia, osmophobia as well as pain perception with the aim of disentangling the underlying mechanisms. There is also more and more evidence that the migraine brain is abnormal even outside of attacks and that repeated attacks are leading to functional and structural alterations in the brain, which may in turn drive the transformation of migraine to its chronic form. Some new results are pinpointing toward a potential role of interesting new brain areas in migraine pathophysiology such as the temporal cortex or the basal ganglia.

SUMMARY

Neuroimaging studies are beginning to shed light on the mechanisms underlying the development and evolution of migraine and its specific symptoms. Future studies have the potential to also improve our understanding of established and upcoming treatment approaches and to monitor treatment effects in an objective and noninvasive way.

Increased susceptibility to cortical spreading depression in the mouse model of familial hemiplegic migraine type 2

Familial hemiplegic migraine type 2 (FHM2) is an autosomal dominant form of migraine with aura that is caused by mutations of the α2-subunit of the Na,K-ATPase, an isoform almost exclusively expressed in astrocytes in the adult brain. We generated the first FHM2 knock-in mouse model carrying the human W887R mutation in the Atp1a2 orthologous gene. Homozygous Atp1a2^R887/R887 mutants died just after birth, while heterozygous Atp1a2^+/R887 mice showed no apparent clinical phenotype. The mutant α2 Na,K-ATPase protein was barely detectable in the brain of homozygous mutants and strongly reduced in the brain of heterozygous mutants, likely as a consequence of endoplasmic reticulum retention and subsequent proteasomal degradation, as we demonstrate in transfected cells. In vivo analysis of cortical spreading depression (CSD), the phenomenon underlying migraine aura, revealed a decreased induction threshold and an increased velocity of propagation in the heterozygous FHM2 mouse. Since several lines of evidence involve a specific role of the glial α2 Na,K pump in active reuptake of glutamate from the synaptic cleft, we hypothesize that CSD facilitation in the FHM2 mouse model is sustained by inefficient glutamate clearance by astrocytes and consequent increased cortical excitatory neurotransmission. The demonstration that FHM2 and FHM1 mutations share the ability to facilitate induction and propagation of CSD in mouse models further support the role of CSD as a key migraine trigger.

We previously reported that mutations of the α2 subunit of the Na,K-ATPase cause familial hemiplegic migraine type 2 (FHM2), a dominant form of migraine with aura. This paper describes the first animal model of FHM2 and represents the further proceeding in this disease investigation. Homozygous knock-in mutant mice die just after birth, while heterozygous mice show no apparent clinical phenotype. However, in vivo analysis revealed a marked facilitation of cortical spreading depression (CSD), the phenomenon underlying migraine aura. Given the evidence for specific functional coupling between the glial α2 Na,K pump and glutamate transporters, we hypothesize that CSD facilitation in the FHM2 mouse model is sustained by inefficient glutamate clearance by astrocytes and consequent increased cortical excitatory neurotransmission. We finally propose this FHM2 mouse as a valuable in vivo model to investigate migraine mechanisms and, possibly, treatments.