Brainstem activation specific to migraine headache

DTI findings during spontaneous migraine attacks

PURPOSE

Previous functional neuroimaging studies showed that the brainstem may have an important role in migraine and recently, DTI studies demonstrated that structural alterations in migraineurs may extend beyond the normal appearing brain tissue. The aim of our study was to find out if DTI may detect any abnormality during the spontaneous migraine attacks.

METHODS

The DTI images obtained in a 3T system during spontaneous migraine episodes. Patients with any systemic or metabolic disorder and abnormal signal intensity in conventional sequences were excluded. We measured the FA and ADC values of red nuclei, periaquaductal gray matter, thalami, posterior limbs of internal capsules and subcortical white matter. Fifteen healthy volunteers served as control group.

RESULTS

Fourteen patients enrolled in the study. The only site where we found an abnormality was the red nuclei, where the ADC values in migraineurs were statistically higher than in healthy volunteers. There was no statistical correlation between the DTI measurements and patients' ages, duration of disease, frequency of attacks and localization of pain.

CONCLUSION

Our findings supported the findings of previous functional neuroimaging studies, which concluded that the brainstem might have a role in the pathogenesis of a migraine episode. We think that the increase of ADC values in red nuclei may reflect vasogenic edema, which cannot be detected in conventional sequences. However, the exact underlying mechanism for this observation is unclear and we do not know whether these changes are responsible for triggering an attack or if they are the consequents of the attack itself.

The enigma of the dorsolateral pons as a migraine generator

In this editorial, we integrate improved understanding of functional and structural brain stem anatomy with lessons learned from other disciplines on brainstem function to provide an alternative interpretation to the data used to support the brainstem migraine generator theory.

Sensitization of the trigeminovascular pathway: perspective and implications to migraine pathophysiology

Migraine headache is commonly associated with signs of exaggerated intracranial and extracranial mechanical sensitivities. Patients exhibiting signs of intracranial hypersensitivity testify that their headache throbs and that mundane physical activities that increase intracranial pressure (such as bending over or coughing) intensify the pain. Patients exhibiting signs of extracranial hypersensitivity testify that during migraine their facial skin hurts in response to otherwise innocuous activities such as combing, shaving, letting water run over their face in the shower, or wearing glasses or earrings (termed here cephalic cutaneous allodynia). Such patients often testify that during migraine their bodily skin is hypersensitive and that wearing tight cloth, bracelets, rings, necklaces and socks or using a heavy blanket can be uncomfortable and/or painful (termed her extracephalic cutaneous allodynia). This review summarizes the evidence that support the view that activation of the trigeminovascular pathway contribute to the headache phase of a migraine attack, that the development of throbbing in the initial phase of migraine is mediated by sensitization of peripheral trigeminovascular neurons that innervate the meninges, that the development of cephalic allodynia is propelled by sensitization of second-order trigeminovascular neurons in the spinal trigeminal nucleus which receive converging sensory input from the meninges as well as from the scalp and facial skin, and that the development of extracephalic allodynia is mediated by sensitization of third-order trigeminovascular neurons in the posterior thalamic nuclei which receive converging sensory input from the meninges, facial and body skin.

Cortical excitability in chronic migraine

A proportion of episodic migraine patients experiences a progressive increase in attack frequency leading to chronic migraine (CM). The most frequent external factor that leads to headache chronification is medication overuse. The neurobiological bases of headache chronification and of the vicious circle of medication overconsumption are not completely elucidated. More recently, the same neurophysiological methods used to study episodic migraine were applied to CM and medication-overuse headache (MOH). Studies of cortical responsivity tend overall to indicate an increase in excitability, in particular of somatosensory and visual cortices, reflected by increased amplitude of evoked responses, decreased activity of inhibitory cortical interneurons reflected in the smaller magnetic suppression of perceptual accuracy, and, at least for visual responses, an increase in habituation. In MOH, overconsumption of triptans or NSAIDs influences cortical excitability differently. Generalized central sensitization is suggested to play an important role in the pathophysiology of headache chronification.

Obesity and chronic daily headache

Obesity may be the greatest epidemic of modern times. It leads to diabetes and heart disease and shortens lifespan. Although not a risk factor for migraine, it is associated with an increased frequency and intensity of migraine. Obesity is also comorbid with chronic daily headache and is a major risk factor for chronification of episodic migraine in adults and children. Although obesity is not a factor in the effectiveness of migraine treatment, it does increase the peripheral and central events in migraine, ultimately increasing the neurologic potential for migraine. Although evidence suggests that obesity is a modifiable risk factor for migraine progression, it is unknown if weight loss is related to decrease in headache frequency. Recent surgical results suggest that this is true. We suggest all possible effective techniques aimed at weight loss be undertaken for migraineurs, especially obese migraineurs, and that carefully monitoring weight changes should be routinely done as part of their migraine care.

Visual cortex excitability and plasticity associated with remission from chronic to episodic migraine

OBJECTIVE

Previous magnetoencephalographic (MEG) studies showed different P100m (where 'm' denotes the magnetic counterpart of P100 in conventional visual evoked potentials) responses between episodic migraine (EM) and chronic migraine (CM) interictally. This study investigated the changes of visual P100m in CM patients who remitted to EM from CM after treatment.

METHODS

At baseline, 25 patients with CM were studied interictally. For each patient, 30 sequential blocks of 50 P100m responses were obtained by MEG. Sub-averaged amplitudes at blocks 2, 9, 16, 23 and 30 were further compared with that at block 1 to assess response habituation or potentiation (i.e. significant decrease or increase at either block vs block 1). The same study was repeated in those patients who remitted from CM to EM after topiramate treatment.

RESULTS

In total, 10 CM patients remitted to EM after treatment. In the follow-up study of these patients during the interictal stage, the P100m at block 1 decreased in amplitude from 53.6 ± 6.6 nAm before remission to 43.0 ± 5.1 nAm (p = 0.028), and the responses at subsequent blocks switched from habituation (amplitude block 30 < block 1 before remission, p = 0.011) to potentiation (block 2 > block 1, p = 0.028).

CONCLUSION

The pattern of P100m responses to consecutive stimulation changes with the transition from CM to EM. Visual cortex plasticity might be a potential biomarker reflecting clinical remission of CM.

Where does a migraine attack originate? In the brainstem

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

Occipital nerve stimulation for medically refractory hypnic headache

OBJECTIVE

Hypnic headache is a rare, primary headache disorder that exclusively occurs regularly during sleep. We present a case of hypnic headache successfully managed with occipital nerve stimulation.

MATERIALS AND METHODS

A 64-year-old female presented with a four-year history of a right occipital headache that regularly awakened her from sleep. The headache, which was dull and throbbing, would awaken her regularly at 4:00 am, five hours after bedtime at 11:00 pm. No photophobia, nausea or vomiting, lacrimation, or other autonomic symptoms were present. The headache was refractory to various medical treatments, including indomethacin, flunarizine, propranolol. She underwent a trial of occipital nerve stimulation with a lead electrode using a medial approach.

RESULTS

During the ten-day trial stimulation, she reported almost complete relief from hypnic headache. Chronic occipital nerve stimulation replicated the trial results. The attacks of hypnic headache recurred in one year with loss of stimulation-induced paresthesia; a subsequent x-ray showed electrode migration. After revision of the electrode to the original location, the effectiveness of the occipital nerve stimulation against hypnic headache was achieved again, and this effect has been consistent through 36 months of follow-up.

CONCLUSION

Occipital nerve stimulation was effective in a patient with chronic, refractory hypnic headache.

Chronic pain and depression in the quality of life of women with migraine--a controlled study

BACKGROUND

Migraine is comorbid to depression and widespread chronic pain (WCP), but the influence of these conditions on the health-related quality of life (HRQoL) of individuals with episodic (EM) and chronic migraine (CM) is poorly understood.

OBJECTIVE

To assess the prevalence of depressive symptoms and WCP in individuals with EM and CM, as well as to estimate the joint impact of these conditions on the HRQoL of these individuals.

METHODS

All women aged 18 to 65 years with a first diagnosis of EM or CM from September of 2006 to September of 2008 seen in an outpatient headache service were invited to participate. They were asked to attend a separate appointment in the service, and to bring another woman of similar age that also agreed to participate. Depressive symptoms were assessed using the Beck Depression Inventory. Questions about WCP followed the protocol of the American College of Rheumatology. HRQoL was assessed using the Short-Form 36 (SF-36). Multivariate analysis modeled HRQoL as a function of headache status, depressive symptoms, and pain, using quantile regression.

RESULTS

Sample consisted of 179 women, 53 in the EM group, 37 in the CM group and 89 in control group. Groups did not differ by demographics. Mean scores of SF-36 were 53.6 (standard deviation [SD] = 23.5) for EM, 44.2 (SD = 18.5) for CM and 61.8 (SD = 21.5) for controls. In multivariate analysis, SF-36 scores were predicted by a CM status (P = .02; -10.05 [95% CI -18.52; -1.58]) and by a Beck Depression Inventory score (P < .01; -1.27 [95% CI -1.55; -0.99]). The influence of WCP in the SF-36 scores approached significance (P = .08; -0.78 [95% CI -1.64; 0.88]). Age did not contribute to the model.

CONCLUSION

Women with migraine are at an increased chance of WCP, and the chance increases as a function of headache frequency. Both depressive symptoms and CM independently predict HRQoL status.

Altered functional magnetic resonance imaging resting-state connectivity in periaqueductal gray networks in migraine

OBJECTIVE

The periaqueductal gray matter (PAG), a known modulator of somatic pain transmission, shows evidence of interictal functional and structural abnormalities in migraineurs, which may contribute to hyperexcitability along spinal and trigeminal nociceptive pathways, and lead to the migraine attack. The aim of this study was to examine functional connectivity of the PAG in migraine.

METHODS

Using resting-state functional MRI, we compared functional connectivity between PAG and a subset of brain areas involved in nociceptive/somatosensory processing and pain modulation in 17 subjects with migraine, during a pain-free state, versus 17 gender- and age-matched controls. We also assessed the relation between intrinsic resting-state correlations within PAG networks and the average monthly frequency of migraine attacks, as well as allodynia.

RESULTS

Our findings show stronger connectivity between the PAG and several brain areas within nociceptive and somatosensory processing pathways in migraineurs versus controls. In addition, as the monthly frequency of migraine attacks worsens, the strength of the connectivity in some areas within these pathways increases, whereas a significant decrease in functional resting-state connectivity between the PAG and brain regions with a predominant role in pain modulation (prefrontal cortex, anterior cingulate, amygdala) can be evidenced. Finally, migraineurs with a history of allodynia exhibit significantly reduced connectivity between PAG, prefrontal regions, and anterior cingulate compared to migraineurs without allodynia.

INTERPRETATION

These data reveal interictal dysfunctional dynamics within pain pathways in migraine manifested as an impairment of the descending pain modulatory circuits, likely leading to loss of pain inhibition, and hyperexcitability primarily in nociceptive areas.

Cerebral perfusion changes in migraineurs: a voxelwise comparison of interictal dynamic susceptibility contrast MRI measurements

INTRODUCTION

The increased risk of cerebro- and cardiovascular disease in migraineurs may be the consequence of a systemic condition affecting whole body vasculature. At cerebrovascular level, this may be reflected by interictal global or regional cerebral perfusion abnormalities. Whether focal perfusion changes occur during interictal migraine has not been convincingly demonstrated.

METHODS

We measured brain perfusion with dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) in 29 interictal female migraineurs (12 migraine with aura (MA), 17 migraine without aura (MO)), and 16 female controls. Perfusion maps were compared between these groups with a voxelwise (p < 0.001, uncorrected, minimum cluster size 20 voxels) and a region-of-interest approach.

RESULTS

In whole brain voxelwise analyses interictal hyperperfusion was observed in the left medial frontal gyrus in migraineurs and in the inferior and middle temporal gyrus in MO patients, in comparison with controls. Hypoperfusion was seen in the postcentral gyrus and in the inferior temporal gyrus in MA patients and in the inferior frontal gyrus in MO patients. Additional focal sites of hyperperfusion were noted in subgroups based on attack frequency and disease history. Region-of-interest analyses of the pons, hypothalamus, occipital lobe, and cerebellum did not show interictal perfusion differences between migraineurs and controls.

CONCLUSIONS

We conclude that interictal migraine is characterized by discrete areas of hyper- and hypoperfusion unspecific for migraine pathophysiology and not explaining the increased vulnerability of particular brain regions for cerebrovascular damage.

Neuroimaging in cluster headache and other trigeminal autonomic cephalalgias

The central nervous system mechanisms involved in trigeminal autonomic cephalalgias, a group of primary headaches characterized by strictly unilateral head pain that occurs in association with ipsilateral craniofacial autonomic features, are still not comprehensively understood. However, functional imaging methods have revolutionized our understanding of mechanisms involved in these primary headache syndromes. The present review provides a brief overview of the major modern functional neuroimaging techniques used to examine brain structure, biochemistry, metabolic state, and functional capacity. The available functional neuroimaging data in cluster headache and other TACs will thus be summarized. Although the precise brain structures responsible for these primary headache syndromes still remain to be determined, neuroimaging data suggest a major role for posterior hypothalamus activation in initiating and maintaining attacks. Furthermore, pathophysiological involvement of the pain neuromatrix and of the central descending opiatergic pain control system was observed. Given the rapid advances in functional and structural neuroimaging methodologies, it can be expected that these non-invasive techniques will continue to improve our understanding into the nature of the brain dysfunction in cluster headache and other trigeminal autonomic cephalalgias.

Calcitonin gene-related peptide (CGRP) and its receptor components in human and rat spinal trigeminal nucleus and spinal cord at C1-level

Background

Calcitonin gene-related peptide (CGRP) has a key role in migraine pathophysiology and is associated with activation of the trigeminovascular system. The trigeminal ganglion, storing CGRP and its receptor components, projects peripheral to the intracranial vasculature and central to regions in the brainstem with Aδ- and C-fibers; this constitutes an essential part of the pain pathways activated in migraine attacks. Therefore it is of importance to identify the regions within the brainstem that processes nociceptive information from the trigeminovascular system, such as the spinal trigeminal nucleus (STN) and the C1-level of the spinal cord. Immunohistochemistry was used to study the distribution and relation between CGRP and its receptor components - calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) - in human and rat STN and at the C1-level, using a set of newly well characterized antibodies. In addition, double-stainings with CGRP and myelin basic protein (MBP, myelin), synaptophysin (synaptic vesicles) or IB4 (C-fibers in general) were performed.

Results

In the STN, the highest density of CGRP immunoreactive fibers were found in a network around fiber bundles in the superficial laminae. CLR and RAMP1 expression were predominately found in fibers in the spinal trigeminal tract region, with some fibers spanning into the superficial laminae. Co-localization between CGRP and its receptor components was not noted. In C1, CGRP was expressed in fibers of laminae I and II. The CGRP staining was similar in rat, except for CGRP positive neurons that were found close to the central canal. In C1, the receptor components were detected in laminae I and II, however these fibers were distinct from fibers expressing CGRP as verified by confocal microscopy.

Conclusions

This study demonstrates the detailed expression of CGRP and its receptor components within STN in the brainstem and in the spinal cord at C1-level, and shows the possibility of CGRP acting postjunctionally in these areas putatively involved in primary headaches.

The biological basis of headache

This article covers the remarkable recent decades as clinicians and scientists have grappled with understanding headache. It is a challenge to understand how a 'normal' brain can become dysfunctional, incapacitating an individual, and then become 'normal' again. Does the answer lie in the anatomy, electrical pathways, the chemistry or a combination? How do the pieces fit together? The components are analyzed in this article. Animal models have provided potential answers. However, these processes have never been proven in man. The dynamic imaging of pain and headache is rapidly evolving and providing new insights and directions of research.

Interictal cortical reorganization in episodic migraine without aura: an event-related fMRI study during parametric trigeminal nociceptive stimulation

The aim of our study was to explore the pain processing network in patients with migraine during trigeminal nociceptive stimulation. Sixteen patients with episodic migraine without aura and 16 healthy controls performed functional magnetic resonance imaging during thermal stimuli (at 41, 51 and 53°C). Patients with migraine showed a greater activation in the perigenual part of anterior cingulate cortex at 51°C and less activation in the bilateral somatosensory cortex at 53°C compared to healthy controls. There were no differences in experimental pain perception between groups. Our findings demonstrate a functional reorganization of cerebral areas known to be involved in pain processing in patients with migraine.

Possible sites of action of the new calcitonin gene-related peptide receptor antagonists

Migraine is considered a neurovascular disease affecting more than 10% of the general population. Currently available drugs for the acute treatment of migraine are vasoconstrictors, which have limitations in their therapeutic use. The calcitonin gene-related peptide (CGRP) has a key role in migraine, where levels of CGRP are increased during acute migraine attacks. CGRP is expressed throughout the central and peripheral nervous system, consistent with control of vasodilatation and transmission of nociceptive information. In migraine, CGRP is released from the trigeminal system. At peripheral synapses CGRP results in vasodilatation via receptors on the smooth muscle cells. At central synapses, CGRP acts postjunctionally on second-order neurons to transmit pain centrally via the brainstem and midbrain to higher cortical pain regions. The recently developed CGRP-receptor antagonists have demonstrated clinical efficacy in the treatment of acute migraine attacks. A remaining question is their site of action. The CGRP-receptor components (calcitonin receptor-like receptor, receptor activity modifying protein 1 and receptor component protein) are found to colocalize in the smooth muscle cells of intracranial arteries and in large-sized neurons in the trigeminal ganglion. The CGRP receptor has also been localized within parts of the brain and the brainstem. The aim of this paper is to review recent localization studies of CGRP and its receptor components within the nervous system and to discuss whether these sites could be possible targets for the CGRP-receptor antagonists.

Pain processing in medication overuse headache: a functional magnetic resonance imaging (fMRI) study

OBJECTIVE

The primary aim was to investigate functional differences between medication overuse headache (MOH) patients and controls with the purpose of evaluating the presence of a global alteration in the processing of noxious stimuli throughout the pain matrix. The secondary aim was to investigate whether activations in MOH patients normalize after medication withdrawal, which would suggest a possible role of the pain matrix in headache chronification.

DESIGN

Functional magnetic resonance imaging was performed during painful mechanical stimulation in nine female patients with MOH immediately and at 6 months after beginning medication withdrawal, and in nine control participants.

RESULTS

Compared with controls, immediately after beginning withdrawal, the MOH patients showed reduced pain-related activity across the primary somatosensory cortex, inferior parietal lobule, and supramarginal gyrus, as well as in regions of the lateral pathway of the pain matrix. At 6 months, these differences were no longer detectable.

CONCLUSION

Our findings suggest that significant functional changes occur in the lateral pain pathway in MOH patients. These could result from different processes: 1) cortical down-regulation aimed at reducing painful input to the cortex; 2) activity-dependent plasticity induced by excessive painful input during migraine attacks; and 3) direct effect of medication overuse. At 6 months after withdrawal, activity in these regions normalized, suggesting that no irreversible changes occur due to medication overuse.

What initiates a migraine attack? Conclusions from four longitudinal studies of quantitative EEG and steady-state visual-evoked potentials in migraineurs

OBJECTIVES

Quantitative electroencephalograpic (QEEG) frequency spectra and steady-state visual-evoked potentials (SSVEP) are indicators of corticothalamic excitability (e.g., arousal). Increased interictal excitability is suggested to be an important element in the migraine pathophysiology. In this paper, we summarize our results from four studies of QEEG and SSVEP recordings in migraineurs interictally and in the days before an attack with the intention to shed light on attack-initiating mechanisms.

MATERIAL AND METHODS

Thirty-two healthy controls, 33 migraineurs without and eight with aura each had three EEGs with photic stimulation on different days. Using the patient headache diaries, we classified the recordings as interictal, preictal, ictal, or post-ictal retrospectively. Interictal recordings were compared pairwise with attack-related EEGs from the same patient as well as with control EEGs. We also correlated clinical variables with the QEEG and SSVEP data.

RESULTS

Between attacks, we found increased relative theta activity and attenuated medium-frequency photic responses in migraineurs without aura compared with those in controls. Within 36 h before the attack, slow and asymmetric EEG activity developed. Increased trigger sensitivity and photophobia correlated with higher theta power and depressed photic responses. Attack duration, migraine history duration, and pain intensity were associated with EEG slowing.

CONCLUSIONS

A general tendency toward EEG slowing and depression of photic responses characterized the migraine group. This pattern was also related to increased severity of symptoms. A change in cortical activity occurred within 36 h before attacks. Our results indicate that thalamocortical hypoexcitability is associated with attack initiation and sensory hypersensitivity in migraine.

Basal cutaneous pain threshold in headache patients

The aim of this study was to analyze cutaneous pain threshold (CPT) during the interictal phase in headache patients, and the relationships between headache frequency and analgesic use. A consecutive series of 98 headache patients and 26 sex- and age-balanced controls were evaluated. Acute allodynia (AA) was assessed by Jakubowski questionnaire, and interictal allodynia (IA) by a skin test with calibrated monofilaments. AA is widely known as a symptom more present in migraine than in TTH spectrum: in our study this was confirmed only in cases of episodic attacks. When headache index rises towards chronicization, the prevalence of AA increases in both headache spectrums (χ (2) 13.55; p < 0.01). AA was associated with IA only in cases of chronic headache. When headache becomes chronic, mostly in presence of medication overuse, interictal CPT decreases and IA prevalence increases (χ (2) 20.44; p < 0.01), with closer association than AA. In MOH patients there were no significant differences depending on the diagnosis of starting headache (migraine or tension type headache) and, in both groups, we found the overuse of analgesics plays an important role: intake of more than one daily drug dramatically reduces the CPT (p < 0.05). Thus, when acute allodynia increases frequency, worsens or appears for the first time in patients with a long-standing history of chronic headache, it could reasonably suggest that the reduction of CPT had started, without using a specific practical skin test but simply by questioning clinical headache history. In conclusion, these results indicate that the role of medication overuse is more important than chronicization in lowering CPT, and suggest that prolonged periods of medication overuse can interfere with pain perception by a reduction of the pain threshold that facilitates the onset of every new attack leading to chronicization.

Trigeminal nociceptive transmission in migraineurs predicts migraine attacks

Several lines of evidence suggest a major role of the trigeminovascular system in the pathogenesis of migraine. Using functional magnetic resonance imaging (fMRI), we compared brain responses during trigeminal pain processing in migraine patients with those of healthy control subjects. The main finding is that the activity of the spinal trigeminal nuclei in response to nociceptive stimulation showed a cycling behavior over the migraine interval. Although interictal (i.e., outside of attack) migraine patients revealed lower activations in the spinal trigeminal nuclei compared with controls, preictal (i.e., shortly before attack) patients showed activity similar to controls, which demonstrates that the trigeminal activation level increases over the pain-free migraine interval. Remarkably, the distance to the next headache attack was predictable by the height of the signal intensities in the spinal nuclei. Migraine patients scanned during the acute spontaneous migraine attack showed significantly lower signal intensities in the trigeminal nuclei compared with controls, demonstrating activity levels similar to interictal patients. Additionally we found-for the first time using fMRI-that migraineurs showed a significant increase in activation of dorsal parts of the pons, previously coined "migraine generator." Unlike the dorsal pons activation usually linked to migraine attacks, the gradient-like activity following nociceptive stimulation in the spinal trigeminal neurons likely reflects a raise in susceptibility of the brain to generate the next attack, as these areas increase their activity long before headache starts. This oscillating behavior may be a key player in the generation of migraine headache, whereas attack-specific pons activations are most likely a secondary event.

Evidence for a vascular factor in migraine

OBJECTIVE

It has been suggested that migraine is caused by neural dysfunction without involvement of vasodilatation. Because dismissal of vascular mechanisms seemed premature, we examined diameter of extra- and intracranial vessels in migraine without aura patients.

METHODS

A novel high-resolution direct magnetic resonance angiography imaging technique was used to measure arterial circumference of the extracranial middle meningeal artery (MMA) and the intracranial middle cerebral artery (MCA). Data were obtained at baseline, during migraine attack, and after treatment with the migraine abortive drug sumatriptan (a 5-hydroxytryptamine agonist).

RESULTS

We found dilatation of both MMA and MCA during migraine attack (p = 0.001). Sumatriptan administration caused amelioration of headache (p < 0.001) and contraction of MMA (p < 0.001), but MCA remained unchanged (p = 0.16). Exploratory analysis revealed that in migraine attacks with half-sided headache, there was only dilatation on the headache side of MMA of 12.49% (95% confidence interval [CI], 4.16-20.83%) and of MCA of 12.88% (95% CI, 3.49-22.27%) and no dilatation on the non headache side of MMA (95% CI, -4.27 to 11.53%) and MCA (95% CI, -6.7 to 14.28%). In double-sided headache we found bilateral vasodilatation of both MMA and MCA (p < 0.001).

INTERPRETATION

These data show that migraine without aura is associated with dilatation of extra- and intracerebral arteries and that the headache location is associated with the location of the vasodilatation. Furthermore, contraction of extracerebral and not intracerebral arteries is associated with amelioration of headache. Collectively, these data suggest that vasodilatation and perivascular release of vasoactive substances is an integral mechanism of migraine pathophysiology.

Tracing neural connections to pain pathways with relevance to primary headaches

Background: Symptoms associated with primary headaches are linked to cranial vascular activity and to the central nervous system (CNS).

Review: The central projections of sensory nerves from three cranial vessels are described in order to further understand pain mechanisms involved in primary headaches. Tracers that label small and large calibre primary afferent fibres revealed similar distributions for the central terminations of sensory nerves in the superficial temporal artery, superior sagittal sinus and middle meningeal artery. The sensory nerve fibres from the vessels pass through both the trigeminal and rostral cervical spinal nerves and terminate in the ventrolateral part of the C1-C3 dorsal horns and the caudal and interpolar divisions of the spinal trigeminal nucleus. The C-fibre terminations were located mainly in the superficial layers (Rexed laminae I and II), and the Aδ-fibres terminated in the deep layers (laminae III and IV). The rostral projections from the ventrolateral C1-C2 dorsal horn revealed terminations in the medial and lateral parabrachial nuclei, the cuneiform nucleus, the periaqueductal gray, the deep mesencephalic nucleus, the thalamic posterior nuclear group and its triangular part, and the thalamic ventral posteromedial nucleus. The terminations in the pons and midbrain were predominately bilateral, whereas those in the thalamus were confined to the contralateral side.

Conclusions: The observations, done in rats with the understanding that similar trigeminovascular organization exists in man, reveal vascular projections into the brainstem and some aspects of the central regions putatively involved in the central processing of noxious craniovascular signals.

Update on hemicrania continua

Hemicrania continua (HC) is a rare primary headache syndrome, characterized by unilateral pain and an absolute response to indometacin. Since the term was first coined in 1984, more than 100 cases have been described worldwide. Most recently, detailed case series that provide more detailed information concerning the sometimes complex clinical presentation of HC have been reported. Functional imaging studies suggest a unique pattern of subcortical involvement in HC: contralateral to the pain posterior hypothalamic region, ipsilateral dorsal pons and ipsilateral ventral midbrain, which, along with the particular effect of indometacin, probably justifies its classification as a unique entity. Increasing the awareness of this primary headache form among clinicians will aid in its diagnosis while further work is being undertaken to characterize the syndrome.

Painful heat reveals hyperexcitability of the temporal pole in interictal and ictal migraine States

During migraine attacks, alterations in sensation accompanying headache may manifest as allodynia and enhanced sensitivity to light, sound, and odors. Our objective was to identify physiological changes in cortical regions in migraine patients using painful heat and functional magnetic resonance imaging (fMRI) and the structural basis for such changes using diffusion tensor imaging (DTI). In 11 interictal patients, painful heat threshold + 1°C was applied unilaterally to the forehead during fMRI scanning. Significantly greater activation was identified in the medial temporal lobe in patients relative to healthy subjects, specifically in the anterior temporal pole (TP). In patients, TP showed significantly increased functional connectivity in several brain regions relative to controls, suggesting that TP hyperexcitability may contribute to functional abnormalities in migraine. In 9 healthy subjects, DTI identified white matter connectivity between TP and pulvinar nucleus, which has been related to migraine. In 8 patients, fMRI activation in TP with painful heat was exacerbated during migraine, suggesting that repeated migraines may sensitize TP. This article investigates a nonclassical role of TP in migraineurs. Observed temporal lobe abnormalities may provide a basis for many of the perceptual changes in migraineurs and may serve as a potential interictal biomarker for drug efficacy.

Migraine and cardiovascular disease

Migraine, especially migraine with aura is an established risk factor for ischemic lesions of the brain. Recent evidence has also linked migraine with and without aura to a broader range of ischemic vascular disorders including angina, myocardial infarction, coronary revascularization, claudication and cardiovascular mortality. The topic is therefore of considerable interest. Accordingly, herein we review the association between migraine and cardiovascular disease. We start by briefly presenting diagnostic criteria for migraine and revising its pathophysiology. We follow by summarizing the evidence on the topic. We then briefly present the results of a recent meta-analysis. We close by highlighting results of a large epidemiological study conducted after the publication of the meta-analysis.

Sumatriptan alleviates nitroglycerin-induced mechanical and thermal allodynia in mice

The association between the clinical use of nitroglycerin (NTG) and headache has led to the examination of NTG as a model trigger for migraine and related headache disorders, both in humans and laboratory animals. In this study in mice, we hypothesized that NTG could trigger behavioural and physiological responses that resemble a common manifestation of migraine in humans. We report that animals exhibit a dose-dependent and prolonged NTG-induced thermal and mechanical allodynia, starting 30-60 min after intraperitoneal injection of NTG at 5-10 mg/kg. NTG administration also induced Fos expression, an anatomical marker of neuronal activity in neurons of the trigeminal nucleus caudalis and cervical spinal cord dorsal horn, suggesting that enhanced nociceptive processing within the spinal cord contributes to the increased nociceptive behaviour. Moreover, sumatriptan, a drug with relative specificity for migraine, alleviated the NTG-induced allodynia. We also tested whether NTG reduces the threshold for cortical spreading depression (CSD), an event considered to be the physiological substrate of the migraine aura. We found that the threshold of CSD was unaffected by NTG, suggesting that NTG stimulates migraine mechanisms that are independent of the regulation of cortical excitability.

Interictal metabolic changes in episodic migraine: a voxel-based FDG-PET study

Whereas there are many H(2)(15)O-positron emission tomography (PET) studies demonstrating neuronal activation during acute migraine attacks, little information is available on the interictal (headache-free period) glucose metabolic changes in migraine. We therefore conducted voxel-based statistical parametric mapping analysis of (18)F-fluorodeoxyglucose-PET to evaluate interictal metabolic differences between 20 episodic migraine patients (four with aura; three men; mean age 34.0 +/- 6.4 years) and 20 control subjects. Separate correlation analyses were performed to delineate a possible relationship between regional glucose metabolism and disease duration or lifetime headache frequency in migraine patients. Group comparison showed that migraine patients had significant hypometabolism in several regions known to be involved in central pain processing, such as bilateral insula, bilateral anterior and posterior cingulate cortex, left premotor and prefrontal cortex, and left primary somatosensory cortex (uncorrected P < 0.001, corrected P < 0.05 with small volume corrections). Correlation analyses showed that regional metabolism of the insula and anterior cingulate cortex had significant negative correlations with disease duration and lifetime headache frequency (uncorrected P < 0.001, corrected P < 0.05 with small volume corrections). Our findings of progressive glucose hypometabolism in relation to increasing disease duration and increasing headache frequency suggest that repeated migraine attacks over time lead to metabolic abnormalities of selective brain regions belonging to the central pain matrix.

Persistent ictal-like visual cortical excitability in chronic migraine

Episodic migraine (EM) may evolve into the more disabling chronic migraine (CM, monthly migraine days ≥ 8 and headache days ≥ 15) with unknown mechanism. Aiming to elucidate the pathophysiology of CM and its relationship with EM, this study characterized the visual cortical responses in CM and EM. Neuromagnetic visual-evoked responses to left-hemifield checkerboard reversals were obtained in patients with EM (interictal or ictal states), CM (interictal) and age-matched controls. For each subject, the 1500 evoked responses were sequentially divided into 30 blocks and percentage changes of P100m amplitude in blocks 2, 9, 16, 23, and 30 compared to the first block were computed to assess habituation. At the end of visual stimulation (block 30), P100m amplitude was decreased (habituated) in the controls (n=32) (35.2±2.6nAm vs. 41.9±2.7, p=0.005) but increased (potentiated) in the interictal state of EM (n=29) (39.7±3.8 vs. 33.5±3.0, p=0.007). In CM (n=25), P100m was habituated (46.5±2.9 vs. 51.6±3.7, p=0.013) but higher at the initial block than in those of the interictal state of EM (p=0.001). These CM features also characterized the P100m in the ictal state of EM (n=9). There was no difference of P100m between CM and ictal state of EM. In conclusion, patients with CM demonstrate a persistent ictal-like excitability pattern of the visual cortex between migraine attacks which may implicate central inhibitory dysfunction.

Migraine, tension-type headache, and attention-deficit/hyperactivity disorder in childhood: a population-based study

OBJECTIVES

Primary headache syndromes (eg, migraine and tension-type headache [TTH]) and attention-deficit/hyperactivity disorder (ADHD) are prevalent in childhood and may cause impairment in social and academic functioning. We tested if ADHD or its symptoms are associated with specific headache syndromes or with headache frequency.

STUDY DESIGN

Cross-sectional epidemiological study with direct interviews to parents and teachers using validated and standardized questionnaires.

SETTING

Populational study.

PARTICIPANTS

Children aged 5 to 11 years (n = 1856).

OUTCOME MEASURES

Prevalence of ADHD as a function of headache status in crude and adjusted analyses.

RESULTS

The prevalence of migraine was 3.76%. Infrequent episodic TTH occurred in 2.3% of the sample, and frequent episodic TTH occurred in 1.6%. The prevalence of ADHD was 6.1%. The prevalence of ADHD was not significantly different by headache category. For hyperactivity-impulsivity symptoms, the prevalence was 8.1% in children without headache, 23.7% in children with migraine (relative risk [RR], 2.6; 95% confidence interval [CI], 1.6-4.2), and 18.4% in children with probable migraine (RR, 2.1; 95% CI, 1.4-3.2). For inattention, no significant differences were seen. In multivariate analyses, ADHD or inattention symptoms were not predicted by headache subtypes or headache frequency. Hyperactivity-impulsivity symptoms were significantly associated with any headache (P < 0.01), TTH (P < 0.01), or migraine (P < 0.001).

CONCLUSION

Migraine and TTH are not comorbid to ADHD overall, but are comorbid to hyperactive-impulsive behavior. Providers and educators should be aware of the association.

Cerebellar distribution of calcitonin gene-related peptide (CGRP) and its receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) in rat

Clinical and experimental results have revealed a fundamental role of calcitonin gene-related peptide (CGRP) in primary headaches. CGRP is widely expressed in neurons both in the central nervous system (CNS) and in peripheral sensory nerves. In the CNS there is a wide distribution of CGRP-containing neurons with the highest levels seen in striatum, amygdale and cerebellum. Moreover, in acute attacks of migraine there is evidence of cerebellar activation. To understand the role of CGRP, antibodies towards the CGRP receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein type 1 (RAMP1) have been developed. In the present study we therefore examined immunohistochemically the distribution of CGRP and its receptor components in the cerebellum. CGRP immunoreactivity was only found intracellularly in the cerebellar Purkinje cell bodies, whereas CLR and RAMP1 were detected on the surface of the Purkinje cell bodies and in their processes. The elaborate dendritic tree of Purkinje cell fibers was distinctly visualized with the RAMP1 antibody. In addition, profoundly stained fibers spanning from the molecular layer into the medulla was observed with the RAMP1 antibody. Judged from the high density of immunoreactive cells expressing CGRP, RAMP1 or CLR, and from the double staining of CGRP and RAMP1 it is likely that most, if not all, Purkinje cells express both the peptide and the receptor components. Double staining with RAMP1 and the glial cell markers glial fibrillary acidic protein (GFAP) and S-100 revealed an almost identical staining pattern of the antibodies in the area of the cell body surfaces. However, as judged by confocal microscopy, no double staining was present. Instead, it was discovered that the glial cells tightly surrounded the Purkinje cells which easily could be interpreted as co-localization in the epifluorescence microscope. Our observations demonstrate that there is a rich expression of CGRP and CGRP receptor elements in the cerebellum which points towards a functional role of CGRP in cerebellar Purkinje cells. Recent advances in the biology of the cerebellum indicate that there may be a role in nociception; hence a target of the recently discovered CGRP receptor antagonists that have demonstrated improvement in migraine pain and associated symptoms could be cerebellar CGRP receptors.

Brainstem changes in 5-HT1A receptor availability during migraine attack

BACKGROUND

Among serotonin receptors, 5-HT(1A) receptors are implicated in the regulation of central serotoninergic tone and could be involved in the abnormal brain 5-HT turnover suspected in migraineurs. The aim of this study was to investigate 5-HT(1A) receptors' availability during migraine attacks.

METHODS

Ten patients suffering from odor-triggered migraine attacks and 10 control subjects were investigated using positron emission tomography (PET) and [(18)F]MPPF PET tracer, a selective 5-HT(1A) antagonist. All subjects underwent calibrated olfactory stimulations prior to the PET study.

RESULTS

Four patients developed a migraine attack during the PET study. In these patients, statistical parametrical mapping and region of interest analyses showed an increased [(18)F]MPPF binding potential (BP(ND)) in the pontine raphe when compared to headache-free migraineurs and control subjects. This ictal change was confirmed at the individual level in each of the four affected patients. In comparison with the headache-free migraineurs, patients with a migraine attack also showed significantly increased [(18)F]MPPF BP(ND) in the left orbitofrontal cortex, precentral gyrus and temporal pole. No significant change in [(18)F]MPPF BP(ND) was observed between headache-free migraineurs and controls.

CONCLUSIONS

Our results emphasize the role of 5HT(1A) receptors in the pontine raphe nuclei during the early stage of migraine attacks.

Familial hemicrania continua

There are now three known causative genes for familial hemiplegic migraine and increasing evidence to support a genetic predisposition to the more common types of migraine with and without aura, and for cluster headache. We present the first reported case of familial hemicrania continua. A mother and daughter developed hemicrania continua at the same time of life. Both showed an absolute response to indometacin and at similar doses. Both also suffered from migraine with aura. We discuss the increasing support for a genetic predisposition to dysfunction of the pain system within the brain manifesting as primary headache.

14th International Headache Congress: basic science highlights

During the 14th International Headache Congress the results of several innovative studies that contribute to our understanding of headache pathophysiology and treatment were presented. Here we summarize work expected to contribute substantially to understanding headache mechanisms, while an accompanying manuscript summarizes presentations regarding the treatment of headache. This manuscript highlights research on mechanisms of photophobia and phonophobia, pharmacologic inhibition of cortical spreading depression, a proposed mechanism by which oxygen effectively treats cluster headache, identification of functional and structural aberrations in people with hypnic headache, and research on functional imaging markers of a migraine attack.

Neuroimaging in chronic migraine

In chronic migraine, many neuroimaging studies with advanced techniques showed abnormalities in several brain areas involved in pain processing. The structural and functional dysfunctions are reported in cerebral areas localized in the brainstem and in the lateral and medial pain pathways. Using the advanced technique of volumetric MRI (voxel-based morphometry), reduction in the grey and white matter in brain areas of the pain network and increased density of the structures of the brainstem were observed in patients with episodic or chronic migraine. Most of the studies of functional anatomy in chronic migraine uses positron emission tomography (PET) and functional RM. These techniques could detect cerebral areas with regional cerebral blood flow and blood level oxygenation-dependent (BOLD) signal changes. Several PET and functional MRI experiments in patients with chronic migraine and drugs overuse before and after the withdrawal showed hypometabolism and hypoactivation in cortical areas involved in pain processing. These areas normalize their activity after detoxification, indicating reversible metabolic changes and BOLD signal changes as observed in other chronic pain. Functional and structural alterations observed in the cerebral areas of the pain network could be a result of a selective dysfunction of these regions due to cortical overstimulation associated with chronic pain. Advanced neuroimaging techniques have revolutionized the knowledge on chronic migraine, determining specific cortical substrate that could explain different forms of chronic migraine and perhaps the predisposition of patients to different therapeutic responses and to possible relapse in drug abuse.

[Neuroimaging in medicine]

Neuroimaging has in recent years greatly contributed to our understanding of a wide range of aspects of central neurological diseases. These include the classification and localization of disease (e.g., in headache), the understanding of pathology (e.g., in Parkinson's disease), mechanisms of reorganization (e.g., in stroke), and the subclinical progress of disease (e.g., in degenerative diseases). Apart form presurgical mapping, clinical applications of fMRI are limited. However, functional imaging enables the formulation of neurobiological hypotheses that can be tested clinically and is suited to test classical clinical hypotheses about how the brain works. Understanding the mechanisms and the site of pathology, e.g., in cluster headaches, will lead and has led to new therapeutic strategies. New methodological developments for neuroscientific applications are aimed at the integration of functional and morphological connectivity through a combination of magnetic resonance techniques (fMRI, DTI) and electrophysiological (EEG, MEG) recordings. In addition to stimulus-dependent activations, resting state activity has found increasing interest, for example, in sleep research and various psychiatric diseases (e.g., schizophrenia, borderline).

Deep brain stimulation in cluster headache: hypothalamus or midbrain tegmentum?

Functional and structural neuroimaging studies have provided pivotal insights into the pathophysiology of trigeminal autonomic cephalalgias (TACs), particularly cluster headache (CH). Functional imaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) in TACs have reported activation of the posterior hypothalamus. A structural neuroimaging study using voxel-based morphometry in CH reported increased volume of the hypothalamic gray, although another larger study failed to reproduce this finding. These studies in CH prompted the use of stereotactic stimulation of the target point identified by functional and structural neuroimaging. The precise anatomical localization of the deep brain stimulation (DBS) target places it at the midbrain tegmentum rather than the posterior hypothalamus. A comparison of the PET and fMRI studies in TACs reveals that the diencephalic/mesencephalic activation is more posteroinferior in the PET studies, straddling the hypothalamus and midbrain tegmentum, whereas the activation is centered on the hypothalamus in the higher spatial resolution fMRI studies. To optimize the outcomes from DBS, it is likely that patients will need to be studied individually using functional imaging techniques that have high spatial and temporal resolution to enable targeting of the appropriate locus with stereotactic stimulation.

Thalamic sensitization transforms localized pain into widespread allodynia

OBJECTIVE

Focal somatic pain can evolve into widespread hypersensitivity to nonpainful and painful skin stimuli (allodynia and hyperalgesia, respectively). We hypothesized that transformation of headache into whole-body allodynia/hyperalgesia during a migraine attack is mediated by sensitization of thalamic neurons that process converging sensory impulses from the cranial meninges and extracephalic skin.

METHODS

Extracephalic allodynia was assessed using single unit recording of thalamic trigeminovascular neurons in rats and contrast analysis of blood oxygenation level-dependent (BOLD) signals registered in functional magnetic resonance imaging (fMRI) scans of patients exhibiting extracephalic allodynia.

RESULTS

Sensory neurons in the rat posterior thalamus that were activated and sensitized by chemical stimulation of the cranial dura exhibited long-lasting hyperexcitability to innocuous (brush, pressure) and noxious (pinch, heat) stimulation of the paws. Innocuous, extracephalic skin stimuli that did not produce neuronal firing at baseline (eg, brush) became as effective as noxious stimuli (eg, pinch) in eliciting large bouts of neuronal firing after sensitization was established. In migraine patients, fMRI assessment of BOLD signals showed that brush and heat stimulation at the skin of the dorsum of the hand produced larger BOLD responses in the posterior thalamus of subjects undergoing a migraine attack with extracephalic allodynia than the corresponding responses registered when the same patients were free of migraine and allodynia.

INTERPRETATION

We propose that the spreading of multimodal allodynia and hyperalgesia beyond the locus of migraine headache is mediated by sensitized thalamic neurons that process nociceptive information from the cranial meninges together with sensory information from the skin of the scalp, face, body, and limbs.