A review of diagnostic and functional imaging in headache

Utility of Neuroimaging in the Management of Chronic and Acute Headache

Imaging plays an important role in identifying the cause of the much less common secondary headaches. Such headaches may be caused by a variety of pathologic conditions which can be categorized as intracranial and extracranial. Idiopathic intracranial hypertension imaging findings include "empty sella," orbital changes, and dural venous sinus narrowing. Intracranial hypotension (ICH) is frequently caused by CSF leaks. Imaging findings include loss of the CSF spaces, downward displacement of the brain, as well as dural thickening and enhancement. Severe cases of ICH may result in subdural hematomas. A variety of intracranial and skull base tumors may cause headaches due to dural involvement. Extracranial tumors and lesions that frequently present with headaches include a variety of sinonasal tumors as well as mucoceles. Neurovascular compression disorders causing headaches include trigeminal and glossopharyngeal neuralgia. Imaging findings include displacement and atrophy of the cranial nerve caused by an adjacent arterial or venous structure.

Alteration in Functional Magnetic Resonance Imaging Signal Complexity Across Multiple Time Scales in Patients With Migraine Without Aura

Background

Migraine is a primary neurological disorder associated with complex brain activity. Recently, mounting evidence has suggested that migraine is underpinned by aberrant dynamic brain activity characterized by linear and non-linear changes across a variety of time scales. However, the abnormal dynamic brain activity at different time scales is still unknown in patients with migraine without aura (MWoA). This study aimed to assess the altered patterns of brain activity dynamics over different time scales and the potential pathophysiological mechanisms of alterations in patients with MWoA.

Methods

Multiscale entropy in 50 patients and 20 healthy controls (HCs) was calculated to investigate the patterns and altered brain complexity (BC) across five different time scales. Spearman rank correlation analysis between BC in regions showing significant intergroup differences and clinical scores (i.e., frequency of migraine attacks, duration, headache impact test) was conducted in patients with MWoA.

Results

The spatial distribution of BC varied across different time scales. At time scale1, BC was higher in the posterior default mode network (DMN) across participants. Compared with HCs, patients with MWoA had higher BC in the DMN and sensorimotor network. At time scale2, BC was mainly higher in the anterior DMN across participants. Patients with MWoA had higher BC in the sensorimotor network. At time scale3, BC was mainly higher in the frontoparietal network across participants. Patients with MWoA had increased BC in the parietal gyrus. At time scale4, BC is mainly higher in the sensorimotor network. Patients with MWoA had higher BC in the postcentral gyrus. At time scale5, BC was mainly higher in the DMN. Patients with MWoA had lower BC in the posterior DMN. In particular, BC values in the precuneus and paracentral lobule significantly correlated with clinical symptoms.

Conclusion

Migraine is associated with alterations in dynamic brain activity in the sensorimotor network and DMN over multiple time scales. Time-varying BC within these regions could be linked to instability in pain transmission and modulation. Our findings provide new evidence for the hypothesis of abnormal dynamic brain activity in migraine.

Tele-healthcare in migraine medicine: from diagnosis to monitoring treatment outcomes

INTRODUCTION

: Primary headaches represent a huge cost in terms of decreased productivity and migraine occupies the first position among disabilities in working population. Migraine has a high incidence, disproportionate to the available primary care centres. In most cases, migraine can be managed through the simple and accurate collection of clinical history, which makes it an ideal candidate for tele-healthcare.

AREAS COVERED

: In this narrative review we retrace the most important scientific evidence regarding use of tele-healthcare in headache medicine. Over the last few years, it has proved to be a valid and useful tool for the management of migraine. Furthermore, current pandemic has imposed a drastic change in the way of thinking and setting up medicine, forcing clinicians and patients to a huge expansion of telemedicine.

EXPERT OPINION

: We should permanently insert the culture of telemedicine in the headache care not only in academies and scientific societies, but extend it to specialized hospitals for the treatment of headaches. Only by broadening the old book-based strategy, we will be able to open the door to the multidimensional culture of headache medicine. Experts of excellence centres should set an example and pave the way for the rest of the clinicians.

Information Processing in Migraine: A Review of Studies on P300

Subjective cognitive dysfunction is common among migraineurs. The aim of this review is to evaluate the usefulness of psychophysiology by means of the P300 component of the event-related potential in the understanding of subtle and sub-clinical changes in cognition that may occur during and between migraine episodes. Some P300 studies suggest a potential impairment of information processing, as reflected by only few findings of interictal decreased amplitude and prolonged latency, ictal augmented amplitude and prolonged latency, changes in cognitive habituation, and limited capacity to relocate attention away from painful stimuli. P300 may represent a valuable aid for clinicians to identify patients at risk of chronicization and cognitive weakening due to neurovascular complications; in this perspective a research agenda may be planned involving larger numbers of patients undergoing psychophysiological studies.

Advanced Imaging in the Evaluation of Migraine Headaches

The use of advanced imaging in routine diagnostic practice appears to provide only limited value in patients with migraine who have not experienced recent changes in headache characteristics or symptoms. However, advanced imaging may have potential for studying the biological manifestations and pathophysiology of migraine headaches. Migraine with aura appears to have characteristic spatiotemporal changes in structural anatomy, function, hemodynamics, metabolism, and biochemistry, whereas migraine without aura produces more subtle and complex changes. Large, controlled, multicenter imaging-based observational trials are needed to confirm the anecdotal evidence in the literature and test the scientific hypotheses thought to underscore migraine pathophysiology.

Pharmacogenetic considerations for migraine therapies

INTRODUCTION

Migraine is a common neurological disorder with a complex pathophysiology. It has been estimated that incidence between adults of current headache disorder is about 50%. Different studies show that this condition has an important and complex genetic component in response to drug therapy. Areas covered: This review shows and summarizes the importance of the polymorphisms associated with the major antimigraine drug metabolizing enzymes. The research of bibliographic databases has involved only published peer-reviewed articles from indexed journals. Expert opinion: Pharmacogenetics is based on the identification of polymorphism and promises personalized therapy with efficacy and reduction of adverse events. The association between genotype and an altered metabolizer status could guide clinical decision to evade concomitant treatments and adverse events. The introduction of routine genetic testing could help to choose the efficacy drug on the individual and genetic profile.

Longitudinal assessment of gray matter volumes and white matter integrity in patients with medication-overuse headache

Background Medication-overuse headache is a common clinical entity, but neuroimaging studies investigating volumetric and microstructural alterations of the brain in medication-overuse headache are rare. Therefore, in the current longitidunal study we evaluated gray matter volume and white matter integrity in patients with medication-overuse headache before and after drug withdrawal. Methods A prospective study evaluated 27 patients with medication-overuse headache and 27 age-, sex-, and education-matched healthy adults. High-resolution T1-weighted magnetic resonance imaging and diffusion tensor imaging were obtained from the control group and medication-overuse headache patients before and six months after drug withdrawal. Tract-based spatial statistics of multiple diffusivity indices and voxel-based morphometry were employed to investigate white and gray matter abnormalities. Results No correlation was found between age, gender, education and smoking status in both groups. The most commonly overused medications were simple analgesics (96.3%) and combined analgesics (3.7%). The mean duration of the history of medication overuse and headaches was 56.7 ± 63.5 months. White matter diffusional and gray matter morphological alterations including volume, fractional anisotropy, radial diffusivity, and axial diffusivity analyses showed no significant relationship in the patients before and six months after withdrawal of analgesics. Also no difference was observed between the patients versus controls. Conclusion Our data demonstrated no structural alterations within the brain in medication-overuse headache.

Physiopathology of Migraine: What Have We Learned from Functional Imaging?

PURPOSE OF REVIEW

This review aims to provide an overview of the most recent and significant functional neuroimaging studies which have clarified the complex mechanisms underlying migraine pathophysiology.

RECENT FINDINGS

The recent data allow us to overcome the concept of a migraine generator suggesting that functional networks abnormalities may lead to changes in different brain area activities and consequent reduced migraine thresholds susceptibility, likely associated with higher migraine severity and burden. Although functional magnetic resonance imaging studies have allowed recognition of several migraine mechanisms, its pathophysiology is not completely understood and is still a matter of research. Nevertheless, in recent years, functional magnetic resonance imaging studies have allowed us to implement our knowledge of migraine pathophysiology. The pivotal role of both the brainstem and the hippocampus in the first phase of a migraine attack, the involvement of limbic pathway in the constitution of a migrainous pain network, the disrupted functional connectivity in cognitive brain networks, as well as the abnormal function of the visual network in patients with migraine with aura are the main milestones in migraine imaging achieved through functional imaging advances. We believe that further studies based on combined functional and structural techniques and the investigation of the different phases of migraine cycle may represent an efficient methodological approach for comprehensively looking into the migrainous brain secrets.

Grey matter alterations in migraine: A systematic review and meta-analysis

Objectives

To summarize and meta-analyze studies on changes in grey matter (GM) in patients with migraine. We aimed to determine whether there are concordant structural changes in the foci, whether structural changes are concordant with functional changes, and provide further understanding of the anatomy and biology of migraine.

Methods

We searched PubMed and Embase for relevant articles published between January 1985 and November 2015, and examined the references within relevant primary articles. Following exclusion of unsuitable studies, meta-analysis were performed using activation likelihood estimation (ALE).

Results

Eight clinical studies were analyzed for structural changes, containing a total of 390 subjects (191 patients and 199 controls). Five functional studies were enrolled, containing 93 patients and 96 controls. ALE showed that the migraineurs had concordant decreases in the GM volume (GMV) in the bilateral inferior frontal gyri, the right precentral gyrus, the left middle frontal gyrus and the left cingulate gyrus. GMV decreases in right claustrum, left cingulated gyrus, right anterior cingulate, amygdala and left parahippocampal gyrus are related to estimated frequency of headache attack. Activation was found in the somatosensory, cingulate, limbic lobe, basal ganglia and midbrain in migraine patients.

Conclusion

GM changes in migraineurs may indicate the mechanism of pain processing and associated symptoms. Changes in the frontal gyrus may predispose a person to pain conditions. The limbic regions may be accumulated damage due to the repetitive occurrence of pain-related processes. Increased activation in precentral gyrus and cingulate opposed to GMV decrease might suggest increased effort duo to disorganization of these areas and/or the use of compensatory strategies involving pain processing in migraine. Knowledge of these structural and functional changes may be useful for monitoring disease progression as well as for therapeutic interventions.

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There are some concordant structural changes in migraine.

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Some structural changes like frontal lobe and cingulate are also over-activated in interictal phase.

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Frontal gyrus may predispose a person to pain condition.

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Limbic regions may be accumulating brain damage due to pain-related processes.

Sleep, headaches and cerebral energy control: a synoptic view

INTRODUCTION

The amount of cerebral functions is particularly elevated. This intense activity requires a great expenditure of energy: the restoration of energy is the fundamental function of sleep whilst the slowdown in energy consumption may be considered the physiological effect of primary headaches. The continuous interaction of sleep and primary headaches is possible as they share many anatomical and functional cerebral systems. Areas covered: This review describes how sleep and headaches are reciprocally involved in preservation and restoration of brain energy. Data were obtained from the most relevant and recent works available in PubMed about this topic. Expert commentary: The energetic view of sleep, primary headaches and their relationship may have relevant clinical consequences: the investigation and the modification of the multiple aspects, primarily environmental, that may influence sleep and headache, become mandatory to facilitate the cerebral energy preservation by reducing its consumption and by ensuring its recovery.

The effects of acupuncture treatment on the right frontoparietal network in migraine without aura patients

BACKGROUND

Functional and structural abnormalities in resting-state brain networks in migraine patients have been confirmed by previous functional magnetic resonance imaging (fMRI) studies. However, few studies focusing on the neural responses of therapeutic treatment on migraine have been conducted. In this study, we tried to examined the treatment-related effects of standard acupuncture treatment on the right frontoparietal network (RFPN) in migraine patients.

METHODS

A total of 12 migraine without aura (MWoA) patients were recruited to undergo resting-state fMRI scanning and were rescanned after 4 weeks standard acupuncture treatment. Another 12 matched healthy control (HC) subjects underwent once scanning for comparison. We analyzed the functional connectivity of the RFPN between MWoA patients and HC subjects before treatment and that of the MWoA patients before and after treatment. Diffusion tensor images (DTI) data analyzing was also performed to detect fiber-related treatment responses.

RESULTS

We observed significantly decreased FC in the RFPN and that the decreased FC could be reversed by acupuncture treatment. The changes of FC in MWoA patients was negatively correlated with the decrease of visual analogue scale (VAS) scores after treatment. This study indicated that acupuncture treatment for MWoA patients was associated with normalizing effects on the intrinsic decreased FC of the RFPN.

CONCLUSIONS

Our study provided new insights into the treatment-related neural responses in MWoA patients and suggested potential functional pathways for the evaluation of treatment in MWoA patients. Future studies are still in need to confirm the current results and to elucidate the complex neural mechanisms of acupuncture treatment.

A meta-analysis of voxel-based morphometric studies on migraine

PURPOSE

To identify consistent results of voxel-based morphometry (VBM) studies in migraine.

METHODS

Whole-brain VBM studies comparing migraine patients with healthy controls (HC) were systematically searched in PubMed, ISI Web of Science, Embase, and Medline databases from January 1990 to Dec 2014. Coordinates were extracted from clusters with significant difference in gray matter volume (GMV) between migraine patients with healthy controls (HC). Meta-analysis was performed using activation likelihood estimation (ALE).

RESULTS

A total of 5 studies, comprising 126 migraineurs, including 23 migraine with aura, 41migraine without aura, 11 epidemic migraine and 16 chronic migraine as well as 19 Mm and 16 nmM, and 134 HC, were enrolled. The included studies report GMV reduction at 84 coordinates in migraine, as well as GMV increase at 2 coordinate in migraine. However, due to only two included studies have classified patients into these two phenotypes and one stated they included only migraine with aura patients , we were not able to perform a subgroup analysis and separate meta-analyses on each phenotype.

CONCLUSION

There were significant reductions in Middle frontal cortex (BA6, 9) structures and the Inferior frontal cortex (BA44) in migraine. These changes of GMV may indicate the mechanisms of the associated symptoms such as cognitive dysfunction, emotion problems and autonomic dysfunction. But whether this is the characteristics of the subtypes of migraine or can distinguish the types of migraine or primary headache, further studies examining larger samples may better elucidate the changes related to the illness and highlight its pathological mechanism.

Air pollution and daily clinic visits for headache in a subtropical city: Taipei, Taiwan

This study was undertaken to determine whether there was an association between air pollutant levels and daily clinic visits for headache in Taipei, Taiwan. Daily clinic visits for headache and ambient air pollution data for Taipei were obtained for the period from 2006–2011. The odds ratio of clinic visits for headache was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. In the single pollutant models, on warm days (≥23 °C) statistically significant positive associations were found for increased rate of headache occurrence and levels of particulate matter (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃). On cool days (<23 °C), all pollutants were significantly associated with increased headache visits except SO₂. For the two-pollutant models, PM₁₀, O₃ and NO₂ were significant for higher rate of headache visits in combination with each of the other four pollutants on cool days. On warm days, CO remained statistically significant in all two-pollutant models. This study provides evidence that higher levels of ambient air pollutants increase the risk of clinic visits for headache.

Air pollution and daily clinic visits for migraine in a subtropical city: Taipei, Taiwan

This study was undertaken to determine whether there was an association between air pollutant levels and daily clinic visits for migraine in Taipei, Taiwan. Daily clinic visits for migraine and ambient air pollution data for Taipei were obtained for the period 2006-2011. The relative risk of clinic visits for migraine was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. In the single-pollutant models, on warm days (>23°C) statistically significant positive associations were found for increased rate of migraine occurrence and levels of particulate matter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3). On cool days (<23°C), all pollutants were significantly associated with increased migraine visits except CO and SO2. For the two-pollutant models, O3 and NO2 were significant for higher rate of migraine visits in combination with each of the other four pollutants on cool days. On warm days, CO remained statistically significant in all two-pollutant models. This study provides evidence that higher levels of ambient air pollutants enhance the risk of clinic visits for migraine.

The role of BOLD-fMRI in elucidating migraine pathophysiology

Migraine is a neurologic disorder characterized by disabling attacks of throbbing headache with specific features and associated symptoms. Despite the recent discoveries in basic neurosciences, migraine pathophysiology is not completely understood. Nevertheless, in the last decades, advances in functional magnetic resonance imaging (fMRI) have significantly provided new insights into migraine mechanisms. Blood oxygen level dependent (BOLD) fMRI technique is the most commonly used method to explore brain function and connectivity due to high temporal and spatial resolution. The purpose of this review is to present a synthesis of recent BOLD-fMRI studies which have allowed us to elucidate the complex process involved in migraine pathophysiology.

Cortical spreading depression and central pain networks in trigeminal nuclei modulation: time for an integrated migraine pathogenesis perspective

The role of the cortical spreading depression (CSD)-dependent trigeminovascular activation in migraine etiopathogenesis, long considered paradigmatic, has remained substantially unproven in humans. The parallel advancement of functional neuroimaging techniques promoted the extensive exploration of the brain networks involved in pain processing in search of a possible central migraine generator. However, despite initial enthusiasms, it has not been possible to clarify whether the functional central "markers" of pain observed in primary headaches could be considered as causative or just the neural correlates of the ongoing pain. Nonetheless, our knowledge on the complex interactions between CSD, neurogenic inflammation, peripheral trigeminovascular input, central cortico-trigeminal nuclei direct modulation and pain processing and limbic system networks has enormously grown, allowing the reconceptualisation of migraine from a neurovascular to a pure neurolimbic pain disorder, therefore relocating it in the much broader frame of the brain and whole organism homeostatic control. In this work, the available evidences currently supporting the relevance of CSD, of peripheral trigeminovascular input and of direct cortico-trigeminal nuclei modulation in migraine pathogenesis are reviewed in the light of a possible integrated migraine etiopathogenetic perspective.

Pharmacological neuroimaging in headache and pain

PURPOSE OF REVIEW

The current review gives an overview about recent advances in neuroimaging studies with specific emphasis on pharmacological modulation of pain and headache. Further, we want to highlight how imaging methods have changed our understanding of chronic pain and discuss how pharmacological MRI could lead to new insights into underlying mechanisms of headache and pain.

RECENT FINDINGS

Several studies from different imaging laboratories have highlighted the outstanding role of imaging in getting a deeper insight regarding the central mechanisms of drugs. Neuroimaging techniques start to unravel how analgesic drugs, antidepressants or NSAIDs act on pain perception and in particular on central pain processes. Furthermore, the studies included in this review show how context dependent drugs act and how differently they reveal their action in the human brain.

SUMMARY

Imaging techniques give us the opportunity to gain a better understanding of drug processes in the central nervous system and help to understand where drugs reveal their therapeutic effect. While some substances work on the emotional-affective component of pain, others modulate sensory-discriminative pain pathways. Especially in the field of headache research, still a lot has to be done to understand how preventatives and acute medication modulate the human brain. Future studies should also replicate and extend recent findings.

Migraine generator network and spreading depression dynamics as neuromodulation targets in episodic migraine

Migraine is a common disabling headache disorder characterized by recurrent episodes sometimes preceded or accompanied by focal neurological symptoms called aura. The relation between two subtypes, migraine without aura (MWoA) and migraine with aura (MWA), is explored with the aim to identify targets for neuromodulation techniques. To this end, a dynamically regulated control system is schematically reduced to a network of the trigeminal nerve, which innervates the cranial circulation, an associated descending modulatory network of brainstem nuclei, and parasympathetic vasomotor efferents. This extends the idea of a migraine generator region in the brainstem to a larger network and is still simple and explicit enough to open up possibilities for mathematical modeling in the future. In this study, it is suggested that the migraine generator network (MGN) is driven and may therefore respond differently to different spatio-temporal noxious input in the migraine subtypes MWA and MWoA. The noxious input is caused by a cortical perturbation of homeostasis, known as spreading depression (SD). The MGN might even trigger SD in the first place by a failure in vasomotor control. As a consequence, migraine is considered as an inherently dynamical disease to which a linear course from upstream to downstream events would not do justice. Minimally invasive and noninvasive neuromodulation techniques are briefly reviewed and their rational is discussed in the context of the proposed mechanism.

Relevance of functional neuroimaging studies for understanding migraine mechanisms

Advances in imaging have provided further insights into the complex migraine pathophysiology. Functional neuroimaging by means of PET and functional MRI studies have addressed crucial migraine-related issues, improving our understanding of the circuitry that may be involved in the generation, maintenance and recurrence of pain symptoms in migraine. In the last few years, a growing body of imaging literature has also explored pathophysiology of associated migraine symptoms. Of great interest will be the use of advanced imaging techniques to elucidate neural correlates of migraine prodromal, in order to identify clinical subgroups of migrainous subjects. However, the interpretation of the biological significance of these various functional changes could remain incomplete without a combination of expanding genomic information about neurochemical pathways and genetic polymorphisms linked to specific migraine subtypes. Hopefully, a more detailed picture of the migraine neurobiology will emerge from future neuroimaging studies, which may eventually lead to better and more rational treatments.

A PET study with [11C]AZ10419369 to determine brain 5-HT1B receptor occupancy of zolmitriptan in healthy male volunteers

Aim

To investigate the occupancy at brain 5-hydroxytryptamine (5-HT) 1B receptors in human subjects after administration of the antimigraine drug zolmitriptan.

Methods

Positron emission tomography (PET) studies were undertaken using the radioligand [11C]AZ10419369 in eight control subjects at baseline and after administration of zolmitriptan orodispersible tablets. The subjects were examined after two consecutive administrations of 10 mg zolmitriptan, approximately 1 week apart. Two of the subjects were subsequently examined after administration of 5 mg zolmitriptan. One week after the last administration of zolmitriptan five of the subjects underwent additional PET measurements without drug pretreatment.

Results

After administration of 10 mg zolmitriptan, mean receptor occupancy was 4–5%. No consistent changes in 5-HT1B receptor binding were observed for subjects who received 5 mg zolmitriptan. There was a statistically significant negative relationship between binding potential ( BPND) and plasma concentration of zolmitriptan and the active metabolite 183C91, respectively. All of the five subjects who were examined 1 week after dosing with zolmitriptan showed higher BPND post drug administration compared with baseline.

Conclusion

This is the first demonstration of CNS 5-HT1B receptor occupancy of a triptan. The findings are consistent with the low receptor occupancy previously reported in PET studies with agonists at other G protein coupled receptors.

Reduced fractional anisotropy of corpus callosum modulates inter-hemispheric resting state functional connectivity in migraine patients without aura

Background

Diffusion tensor imaging (DTI) study revealed reduced fractional anisotropy (FA) values in the corpus callosum (CC) in migraine patients without aura. Abnormalities in white matter integrity, particularly in the CC, may affect inter-hemispheric resting state functional connectivity (RSFC). Unfortunately, relatively little is known about the alterations in functional interactions between the cerebral hemispheres during resting state in migraine patients without aura, and even less about how the inter-hemispheric RSFC are affected by the abnormalities of the CC.

Methods and findings

Twenty-one migraine patients without aura and 21 healthy controls participated in this study, age-, sex-, and education-matched. Tract-based spatial statistics (TBSS) was employed to investigate the white matter alterations of the CC. Meanwhile, voxel-mirrored homotopic connectivity (VMHC) was used to compare the inter-hemispheric RSFC differences between the patients and controls. TBSS analysis revealed reduced FA values in the genu and the splenium of CC in patient group. VMHC analysis showed decreased inter-hemispheric RSFC of anterior cingulate cortex (ACC) in migraine patients without aura relative to that of the controls. Furthermore, in migraine patients without aura, the reduced FA values of the genu of CC correlated with the decreased inter-hemispheric RSFC of the ACC.

Conclusions

Our findings demonstrated that the migraine patients without aura showed reduced FA values of the genu of CC and decreased inter-hemispheric RSFC of the ACC. The correlation between the above structural and functional changes suggested that the reduced fractional anisotropy (FA) of CC modulates inter-hemispheric VMHC in migraine patients without aura. Our results demonstrated that the VMHC alterations of ACC can reflect the FA changes of the genu of CC in migraine patients without aura.

Role of nitric oxide in cluster headache

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

Etiopathophysiological assessment of cases with chronic daily headache: A functional magnetic resonance imaging included investigation

BACKGROUND

Chronic daily headache (CDH) has gained little attention in functional neuro-imaging. When no structural abnormality is found in CDH, defining functional correlates between activated brain regions during headache bouts may provide unique insights towards understanding the pathophysiology of this type of headache.

METHODS

We recruited four CDH cases for comprehensive assessments, including history taking, physical examinations and neuropsychological evaluations (The Addenbrooke's Cognitive Evaluation, Beck's Anxiety and Depression Inventories, Pittsburg Sleep Quality Index and Epworth Sleepiness Scale). Visual analogue scale (VAS) was used to self-rate the intensity of headache. Patients then underwent electroencephalography (EEG), transcranial Doppler (TCD) and functional magnetic resonance imaging (fMRI) evaluations during maximal (VAS = 8-10/10) and off-headache (VAS = 0-3/10) conditions. Data were used to compare in both conditions. We also used BOLD (blood oxygen level dependent) -group level activation map fMRI to possibly locate headache-related activated brain regions.

RESULTS

General and neurological examinations as well as conventional MRIs were unremarkable. Neuropsychological assessments showed moderate anxiety and depression in one patient and minimal in others. Unlike three patients, maximal and off-headache TCD evaluation in one revealed increased middle cerebral artery blood flow velocity, at the maximal pain area. Although with no seizure history, the same patient's EEG showed paroxysmal epileptic discharges during maximal headache intensity, respectively. Group level activation map fMRI showed activated classical pain matrix regions upon headache bouts (periaqueductal grey, substantia nigra and raphe nucleus), and markedly bilateral occipital lobes activation.

CONCLUSION

The EEG changes were of note. Furthermore, the increased BOLD signals in areas outside the classical pain matrix (i.e. occipital lobes) during maximal headaches may suggest that activation of these areas can be linked to the increased neural activity or visual cortex hyperexcitability in response to visual stimuli. These findings can introduce new perspective towards more in-depth functional imaging studies in headaches of poorly understood pathophysiology.

Selective decreased grey matter volume of the pain-matrix network in cluster headache

AIM

We assessed the pattern of regional white matter and grey matter abnormalities in patients with cluster headache (CH), using tract-based spatial statistics (TBSS) and voxel-based morphometry (VBM).

METHODS

Using a 3.0 Tesla scanner, dual-echo, diffusion tensor and 3D T1-weighted scan were acquired from 15 patients with episodic CH and 19 healthy controls. TBSS analysis was performed using the FMRIB's Diffusion Toolbox. VBM was performed on the 3D T1-weighted images using SPM8.

RESULTS

No diffusivity and volumetry abnormalities of brain white matter were detected in CH patients. Compared with controls, CH patients showed decreased grey matter volume in the right thalamus, head of the right caudate nucleus, right precentral gyrus, right posterior cingulate cortex, bilateral middle frontal gyrus, right middle temporal gyrus, left inferior parietal lobule and left insula (p < 0.001). They also had increased grey matter volume of the right cuneus. The results did not change after hemisphere mirroring in the five patients with left lateralized attacks. The decreased left middle frontal gyrus volume was significantly correlated with disease duration (r = -0.79, p < 0.001).

CONCLUSION

CH patients experience tissue abnormalities of grey matter regions that are part of the antinociceptive system, which is shared with other chronic pain conditions.

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.

Saccade behaviour in migraine patients

BACKGROUND

Voxel-based morphometry studies in migraine patients showed significant grey matter volume reduction in regions involved in the control of saccadic eye movements. We hypothesized that these changes would be reflected in dysfunctional saccadic behaviour.

METHODS

Saccades were recorded by infrared oculography using three different paradigms (pro-saccade with gap, pro-saccade overlap and anti-saccade with gap). We compared the results for migraine patients (n = 80) with those for controls (n = 87).

RESULTS

No significant differences were found between migraine patients with (n = 46) and without (n = 34) aura. Migraine patients showed a saccadic behaviour that differed from controls in three respects. In migraine patients, the latencies in the pro-saccade with gap paradigm were borderline significantly longer. Moreover, in both the pro-saccade with gap and the pro-saccade overlap paradigm we observed a larger intra-individual variation of the latency in migraine patients. However, the biggest difference was that the patients who received migraine prophylactic therapy made significantly more anti-saccade errors in the anti-saccade with gap paradigm, suggesting that inhibitory saccade control is impaired in migraine patients depending on the severity of the migraine.

CONCLUSION

We suggest a deficient inhibitory control, reflecting an executive dysfunction in the dorsolateral prefrontal cortex or a dysfunction in the cingulate cortex, is present in migraine patients.

Neurologic bases for comorbidity of balance disorders, anxiety disorders and migraine: neurotherapeutic implications

The comorbidity among balance disorders, anxiety disorders and migraine has been studied extensively from clinical and basic research perspectives. From a neurological perspective, the comorbid symptoms are viewed as the product of sensorimotor, interoceptive and cognitive adaptations that are produced by afferent interoceptive information processing, a vestibulo-parabrachial nucleus network, a cerebral cortical network (including the insula, orbitofrontal cortex, prefrontal cortex and anterior cingulate cortex), a raphe nuclear-vestibular network, a coeruleo-vestibular network and a raphe-locus coeruleus loop. As these pathways overlap extensively with pathways implicated in the generation, perception and regulation of emotions and affective states, the comorbid disorders and effective treatment modalities can be viewed within the contexts of neurological and psychopharmacological sites of action of current therapies.

Stress and tension-type headache mechanisms

Stress is widely demonstrated as a contributing factor in tension-type headache (TTH). The mechanisms underlying this remain unclear at present. Recent research indicates the importance of central pain processes in tension-type headache (TTH) pathophysiology. Concurrently, research with animals and healthy humans has begun to elucidate the relationship between stress and pain processing in the central nervous system, including central pain processes putatively dysfunctional in TTH. Combined, these two fields of research present new insights and hypotheses into possible mechanisms by which stress may contribute to TTH. To date, however, there has been no comprehensive review of this literature. The present paper provides such a review, which may be valuable in facilitating a broader understanding of the central mechanisms by which stress may contribute to TTH.

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.

Rizatriptan reduces vestibular-induced motion sickness in migraineurs

A previous pilot study suggested that rizatriptan reduces motion sickness induced by complex vestibular stimulation. In this double-blind, randomized, placebo-controlled study we measured motion sickness in response to a complex vestibular stimulus following pretreatment with either rizatriptan or a placebo. Subjects included 25 migraineurs with or without migraine-related dizziness (23 females) aged 21–45 years (31.0 ± 7.8 years). Motion sickness was induced by off-vertical axis rotation in darkness, which stimulates both the semicircular canals and otolith organs of the vestibular apparatus. Results indicated that of the 15 subjects who experienced vestibular-induced motion sickness when pretreated with placebo, 13 showed a decrease in motion sickness following pretreatment with rizatriptan as compared to pretreatment with placebo (P < 0.02). This significant effect was not seen when subjects were exposed to more provocative vestibular stimulation. We conclude that the serotonin agonist, rizatriptan, reduces vestibular-induced motion sickness by influencing serotonergic vestibular-autonomic projections.

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.

The efficacy of a voxel-based morphometry on the analysis of imaging in schizophrenia, temporal lobe epilepsy, and Alzheimer's disease/mild cognitive impairment: a review

Voxel-based morphometry (VBM) done by means of MRI have provided new insights into the neuroanatomical basis for subjects with several conditions. Recently, VBM has been applied to investigate not only regional volumetric changes but also voxel-wise maps of fractional anisotropy (FA) computed from diffusion tensor imaging (DTI). The aim of this article is to review the recent work using VBM technique in particular focusing on schizophrenia, temporal lobe epilepsy (TLE), and Alzheimer's disease (AD)/mild cognitive impairment (MCI). In patients with schizophrenia, VBM approach detects the structural brain abnormalities that appear normal on conventional MRI. Moreover, this technique also has the potential to emerge as a useful clinical tool for early detection and monitoring of disease progression and treatment response in patients with schizophrenia or AD/MCI. In TLE, VBM approach may help elucidate some unresolved important research questions such as how recurrent temporal lobe seizures affect hippocampal and extrahippocampal morphology. Thus, in the future, large cohort studies to monitor whole brain changes on a VBM basis will lead to a further understanding of the neuropathology of several conditions.

[Chronic pain alters the structure of the brain]

Local morphologic alterations of the brain in areas ascribable to the transmission of pain were recently detected in patients suffering from phantom pain, chronic back pain, irritable bowl syndrome, fibromyalgia and frequent headaches. These alterations were different for each pain syndrome, but overlapped in the cingulate cortex, the orbit frontal cortex, the insula and dorsal pons. As it seems that chronic pain patients have a common "brain signature" in areas known to be involved in pain regulation, the question arises whether these changes are the cause or the consequence of chronic pain. The in vivo demonstration of a loss of brain gray matter in patients suffering from chronic pain compared to age and sex-matched healthy controls could represent the heavily discussed neuroanatomical substrate for pain memory.

Blood pressure changes in migraine patients before, during and after migraine attacks

Migraine attacks are characterized by headaches associated with neurological, gastrointestinal, and autonomic symptoms. A relationship between migraine and hypertension or hypotension is controversial. In this study, we aimed to determine if blood pressure changes were related to migraine attacks. From the outpatient clinic of our neurology department, 62 normotensive migraine patients with and without aura were chosen for study in accordance with the International Headache Society 2004 criteria. A questionnaire including general and specific questions was given to the patients to be filled out during 6 consequent migraine attacks. The patients received a fully automatic digital brachial upper arm sphygmomanometer (Omron M 4-1) to measure the changes in their blood pressure during attacks. The patients were asked to record their blood pressure changes 3 times: (1) just before or very early, (2) during (when headache peaks), and (3) 1 hour after the attack. Twenty-three of the 62 patients (57 women, 5 men) had migraine with aura (22 women and 1 man), and 39 of them did not have aura (35 women and 4 men). There was no statistically significant difference between systolic and diastolic values obtained before or very early, during the peak level, and 1 hour after the end of the attacks (P > 0.05). Although diastolic hypotensive values were not different statistically between groups, when all the patients were considered, diastolic hypotensive values were detected in a considerable number of patients (a total of 115 measurements). In this normotensive migrainous population, we observed that diastolic hypotension before or very early, during, and after migraine attack was the most significant result (5.1%). Although it was not statistically significant, the total number of hypotensive values was remarkable.

Air pollution and hospitalization for headache in Chile

The authors performed a time-series analysis to test the association between air pollution and daily numbers of hospitalizations for headache in 7 Chilean urban centers during the period 2001–2005. Results were adjusted for day of the week and humidex. Three categories of headache—migraine, headache with cause specified, and headache not otherwise specified—were all associated with air pollution. Relative risks for migraine associated with interquartile-range increases in specific air pollutants were as follows: 1.11 (95% confidence interval (CI): 1.06, 1.17) for a 1.15-ppm increase in carbon monoxide; 1.11 (95% CI: 1.06, 1.17) for a 28.97-μg/m³ increase in nitrogen dioxide; 1.10 (95% CI: 1.04, 1.17) for a 6.20-ppb increase in sulfur dioxide; 1.17 (95% CI: 1.08, 1.26) for a 69.51-ppb increase in ozone; 1.11 (95% CI: 1.00, 1.19) for a 21.51-μg/m³ increase in particulate matter less than 2.5 μm in aerodynamic diameter (PM_2.5); and 1.10 (95% CI: 1.04, 1.15) for a 37.79-μg/m³ increase in particulate matter less than 10 μm in aerodynamic diameter (PM₁₀). There was no significant effect modification by age, sex, or season. The authors conclude that air pollution appears to increase the risk of headache in Santiago Province. If the relation is causal, the morbidity associated with headache should be considered when estimating the burden of illness and costs associated with poor air quality.

Abnormal brain processing of pain in migraine without aura: A high-density EEG brain mapping study

In the present study we used high-density EEG brain mapping to investigate spatio-temporal aspects of brain activity in response to experimentally induced muscle pain in 17 patients with migraine without aura and 15 healthy controls. Painful electrical stimuli were applied to the trapezius muscle and somatosensory-evoked potentials were recorded with 128-channel EEG with and without concurrent induced tonic neck/shoulder muscle pain. At baseline, the calculated P300 dipole for single stimuli was localized in the cingulate cortex. In patients, but not in controls, the dipole changed position from baseline to the tonic muscle pain condition (z = 29 mm vs. z = −13 mm, P < 0.001) and from baseline to the post-tonic muscle pain condition (z = 29 mm vs. z = −9 mm, P < 0.001). This may be the first evidence that the supraspinal processing of muscle pain is abnormal in patients with migraine without aura.

What's new in neuroimaging methods?

The rapid advancement of neuroimaging methodology and its growing availability has transformed neuroscience research. The answers to many questions that we ask about how the brain is organized depend on the quality of data that we are able to obtain about the locations, dynamics, fluctuations, magnitudes, and types of brain activity and structural changes. In this review an attempt is made to take a snapshot of the cutting edge of a small component of the very rapidly evolving field of neuroimaging. For each area covered, a brief context is provided along with a summary of a few of the current developments and issues. Then, several outstanding papers, published in the past year or so, are described, providing an example of the directions in which each area is progressing. The areas covered include functional magnetic resonance imaging (fMRI), voxel-based morphometry (VBM), diffusion tensor imaging (DTI), electroencephalography (EEG), magnetoencephalography (MEG), optical imaging, and positron emission tomography (PET). More detail is included on fMRI; its subsections include fMRI interpretation, new fMRI contrasts, MRI technology, MRI paradigms and processing, and endogenous oscillations in fMRI.

Hypothalamic deep-brain stimulation: target and potential mechanism for the treatment of cluster headache

Recently, functional imaging data have underscored the crucial role of the hypothalamus in trigemino-autonomic headaches, a group of severe primary headaches. This prompted the application of hypothalamic deep-brain stimulation (DBS), with the intention to preventing cluster headache (CH) attacks in selected severe therapy-refractory cases. To date, a total of 50 operated intractable CH patients, one patient with short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing and three with atypical facial pain, have been reported. However, it is not apparent why the spontaneous bursts of activation in the inferior posterior hypothalamus result in excruciating head pain, whereas continuous electrical stimulation of the identical area is able to prevent these attacks. Recently, this issue has been addressed by examining 10 operated chronic CH patients, using H(2)(15)O-positron emission tomography and alternately switching the hypothalamic stimulator on and off. The stimulation-induced activation in the ipsilateral posterior inferior hypothalamic grey (the site of the stimulator tip) as well as activation and de-activation in several cerebral structures belonging to neuronal circuits usually activated in pain transmission. These data argue against an unspecific antinociceptive effect or pure inhibition of hypothalamic activity as the mode of action of hypothalamic DBS and suggest functional modulation of the pain-processing network.

Regional grey matter changes in patients with migraine: a voxel-based morphometry study

We used voxel-based morphometry (VBM) to compare grey matter volume (GMV) between 20 migraine patients (five with aura and 15 without aura) with normal conventional magnetic resonance imaging findings and 33 healthy controls matched for age and sex. A separate analysis was also performed to delineate a possible correlation between the GMV changes and the headache duration or lifetime headache frequency. When compared with controls, migraine patients had significant GMV reductions in the bilateral insula, motor/premotor, prefrontal, cingulate cortex, right posterior parietal cortex, and orbitofrontal cortex (P < 0.001, uncorrected for multiple comparisons at a voxel level; corrected P < 0.05 after small volume corrections). All regions of the GMV changes were negatively correlated with headache duration and lifetime headache frequency (P < 0.05, Pearson's correlation test). We found evidence for structural grey matter changes in patients with migraine. Our findings of progressive GMV reductions in relation to increasing headache duration and increasing headache frequency suggest that repeated migraine attacks over time result in selective damage to several brain regions involved in central pain processing.

Pharmacogenetics of migraine: genetic variants and their potential role in migraine therapy

Migraine is a paroxysmal neurological disorder affecting up to 6% of males and 18% of females in the general population, and has been demonstrated to have a strong, but complex, genetic component. Genetic investigation of migraine provides hope that new targets for medications and individual specific therapy will be developed. The identification of polymorphisms or genetic biomarkers for disease susceptibility and treatment should aid in providing a better understanding of migraine pathology and, consequently, more appropriate and efficient treatment for migraineurs. In this review, we will discuss results investigating genetic biomarkers for migraine and their potential role in future therapy planning.