Migraine pain: reflections against vasodilatation

Advances in CGRP Monoclonal Antibodies as Migraine Therapy: A Narrative Review

Migraine is a potentially disabling disorder, yet it remains underdiagnosed and undertreated. The release of the neuropeptide calcitonin gene-related peptide (CGRP) in the trigemino-cerebrovascular system plays a vital role in the evolution of migraine. It enhances peripheral sensitization by mediating neurogenic inflammation and also influences central sensitization. The majority of the drug classes available for migraine prophylaxis are nonspecific and associated with numerous side effects and drug interactions. Anti-CGRP monoclonal antibodies (mAb) are an innovative therapeutic class that fulfills the need for more efficacious and tolerable preventive therapy. While erenumab is a mAb to the CGRP receptor, eptinezumab, fremanezumab, and galcanezumab bind to the CGRP molecule. They decrease the number of headache days and improve disability. Upper respiratory tract infection, nausea, constipation, pain at the site of injection, and fatigue are the associated side effects. CGRP mAbs are an excellent advancement in translational research and are a promising addition in migraine therapy. This article discusses the recent advances in the development of the CGRP mAbs.

Retinal Neurovascular Structural Changes in Optical Coherence Tomography and the Relationship between These Changes and White Matter Hyperintensities in Patients with Migraine

INTRODUCTION

This study aimed to reveal whether retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) inner plexiform layer, and choroidal layer (CL) thicknesses differed in patients with migraine. Optical coherence tomography (OCT) was used to measure these neurovascular structural changes and determine the relationship between these structures and cranial white matter hyperintensities (WMHs).

METHODS

This retrospective comparative registry study included a total of 155 individuals aged 18-55 (mean, 33.50 ± 8.34), consisting of 110 migraine patients and 45 healthy controls.

RESULTS

RNFLs were thinner in the migraine group than the control group but not to a statistically significant degree. However, in both eyes, peripapillary RNLF thickness in some specific quadrants was found to be significantly thinner in the patient group than the control group. GCLs were significantly thinner in the migraine group than the control group. CLs were significantly thicker in the migraine group than in the control group. There was no significant difference between the OCT parameters of patients with and without WMH. An inverse correlation was found between disease duration and CL thickness. CLs were significantly thicker in patients in attack periods than those in attack-free periods. There was no significant difference between the OCT parameters of the migraine with aura and migraine without aura subgroups.

DISCUSSION/CONCLUSIONS

Retinal neural and vascular structures might be affected in migraine sufferers, including those in subgroups. Rebound vasodilation may cause alterations in CL thickness during a migraine attack. Factors other than hypoperfusion may contribute to the pathophysiology responsible for the formation of WMH.

Migraine pharmacology and brain ischemia

Introduction: The aim of this review article was to analyze in details the mechanism of drugs’ effects in the treatment and prevention of a migraine attack, as well as to discuss the hypotheses of migraine pathogenesis.

Migraine attack treatment agents: The main agents for migraine attack treatment have an anti-nociceptive activity.

Agents for migraine preventive treatment: β-blocker propranolol also has anti-serotonin and analgesic activities, and most drugs used for the prophylactic treatment of migraine have a vasodilating activity.

Vascular hypothesis of migraine pathogenesis: Despite numerous studies that have expanded our understanding of migraine pathogenesis, the importance of the vascular component in the pathogenesis of this disease has not questioned yet.

Neurogenic hypotheses of cortical spreading depression: It is necessary to take into account the points of this hypothesis in the context of the pathophysiology of migraine.

Neurochemical serotonin hypotheses of migraine pathogenesis: Serotonin plays an important role in the pathogenesis of migraine.

Trigemino-vascular hypotheses of migraine pathogenesis: The trigemino-vascular hypothesis claims to solve the problem of migraine pain.

Migraine and ischemic brain damage: Migraine is a risk factor for ischemic stroke and cognitive disorders.

Search for the new anti-ischemic anti-migraine preparations: A methodology for the search for new anti-ischemic anti-serotonin drugs for the treatment of migraine is proposed.

Conclusion: Belonging of a drug to one or another pharmacological group does not always correspond to its therapeutic effect on the pathogenetic processes of migraine. Migraine with its variety of forms cannot fit only one of the proposed hypotheses on the pathogenesis of this disease.

Graphical abstract:

Evaluation of Systemic Renin and Angiotensin II Levels in Normal Tension Glaucoma

The purpose of this study was to investigate the function of the renin-angiotensin-aldosterone system (RAAS) in normal tension glaucoma (NTG) patients by measuring the level of renin and angiotensin II (AngII) in the plasma. Twenty-four patients with NTG and 38 control subjects were included in this study. Renin and AngII were measured in the blood samples of all subjects by enzyme-linked immunosorbent assay (ELISA). No significant differences were found in the complete blood count, fasting glucose, low-density lipoprotein (LDL), and high-sensitivity C-reactive protein (hs-CRP) levels between the control and NTG groups. The systemic concentration and variability of the renin concentration in the blood was significantly higher in the NTG group (p = 0.005 and 0.005, respectively). According to multivariate logistic regression analysis, the variability of the renin concentration was associated with NTG (p = 0.006). In conclusion, the systemic concentration and variability of renin levels were elevated in NTG patients. An altered renin concentration could represent a difference in RAAS function in NTG patients.

Ultra-rapid brain uptake of subcutaneous sumatriptan in the rat: Implication for cluster headache treatment

BACKGROUND

In spite of the substantial therapeutic efficacy of triptans, their site of action is still debated. Subcutaneous sumatriptan is the most efficacious symptomatic treatment for cluster headache (CH) patients, showing therapeutic onset within a few minutes after injection even in migraine patients. However, whether subcutaneous sumatriptan is able to reach the CNS within this short time frame is currently unknown.

METHODS

Here, by means of liquid chromatography/mass spectrometry, we investigated peripheral and brain distribution of subcutaneous sumatriptan soon after injection in rats at a dose equivalent to that used in patients. Tissue sumatriptan contents were compared to those of oxazepam, a prototypical lipophilic, neuroactive drug.

RESULTS

We report that sumatriptan accumulated within brain regions of relevance to migraine and CH pathogenesis such as the hypothalamus and the brainstem as soon as 1 and 5 minutes after injection. Notably, sumatriptan brain distribution was faster than that of oxazepam, reaching concentrations exceeding its reported binding affinity for 5HT1_B/D receptors, and in the range of those able to inhibit neurotransmitter release in vivo.

CONCLUSION

Our findings indicate that sumatriptan distributes within the CNS soon after injection, and are in line with prompt pain relief by parenteral sumatriptan in CH patients.

Characteristics of sensory neuronal groups in CGRP-cre-ER reporter mice: Comparison to Nav1.8-cre, TRPV1-cre and TRPV1-GFP mouse lines

Peptidergic sensory neurons play a critical role in nociceptive pathways. To precisely define the function and plasticity of sensory neurons in detail, new tools such as transgenic mouse models are needed. We employed electrophysiology and immunohistochemistry to characterize in detail dorsal root ganglion (DRG) neurons expressing an inducible CGRP^cre-ER (CGRP-cre⁺); and compared them to DRG neurons expressing Nav1.8^cre (Nav1.8-cre⁺), TRPV1^cre (TRPV1-cre⁺) and TRPV1-GFP (V1-GFP⁺). Tamoxifen effectively induced CGRP^cre-ER production in DRG. ≈87% of CGRP^cre-ER-expressing neurons were co-labeled CGRP antibody. Three small and two medium-large-sized (5HT3a⁺/NPY2R^- and NPY2R⁺) neuronal groups with unique electrophysiological profiles were CGRP-cre⁺. Nav1.8-cre⁺ neurons were detected in all CGRP-cre⁺ groups, as well as in 5 additional neuronal groups: MrgprD⁺/TRPA1^-, MrgprD⁺/TRPA1⁺, TRPV1⁺/CGRP^-, vGLUT3⁺ and ≈30% of trkC⁺ neurons. Differences between TRPV1^cre and Nav1.8^cre reporters were that unlike TRPV1-cre⁺, Nav1.8-cre⁺ expression was detected in non-nociceptive vGLUT3⁺ and trkC⁺ populations. Many TRPV1-cre⁺ neurons did not respond to capsaicin. In contrast, V1-GFP⁺ neurons were in 4 groups, each of which was capsaicin-sensitive. Finally, none of the analyzed reporter lines showed cre-recombination in trkB⁺, calbindin⁺, 70% of trkC⁺ or parvalbumin⁺ neurons, which together encompassed ≈20% of Nav1.8-cre^- DRG neurons. The data presented here increases our knowledge of peptidergic sensory neuron characteristics, while showing the efficiency and specificity manipulation of peptidergic neurons by the CGRP^cre-ER reporter. We also demonstrate that manipulation of all C- and A-nociceptors is better achieved with TRPV1-cre reporter. Finally, the described approach for detailed characterization of sensory neuronal groups can be applied to a variety of reporter mice.

Changes in retinal vessel diameters in migraine patients during attack-free period

AIM

To evaluate the retinal vessel diameters in patients with migraine by optical coherence tomography (OCT).

METHODS

In this cross-sectional study, 124 eyes of 62 patients with a diagnosis of unilateral migraine during attack-free period and 42 age- and sex-matched control subjects were included. Migraine patients were divided into the ≤2 migraine attacks per month group and the ≥5 migraine attacks per month group. All subjects underwent complete ophthalmological and neurological examinations before measurements. Retinal vessel diameters and choroidal thickness were examined with the Spectralis OCT.

RESULTS

The mean diameters of the arteries in the eyes on the headache side of control group, ≥5 migraine attacks per month and ≤2 migraine attacks per month group at 480 µm from the optic disk (Raster 3) were 119.54±46.69, 136.68±25.93 and 119.34±31.75 µm respectively with a steady decline to 105.57±32.15, 118.18±31.87 and 108.05±38.77 µm at 1440 µm (Raster 7), the last measurement point, respectively. The retinal artery diameter measurements were significantly increased in ≥5 migraine attacks per month patients at four out of five measured points compared to control group (P<0.05). There were no statistical differences at any of the points of vein measurements. The choroidal thickness measurements were significantly decreased in ≥5 migraine attacks per month patients at all measured points compared to control group (P<0.05).

CONCLUSION

The retinal artery diameter is found to increase significantly and the choroidal thickness is found to decrease in the eyes on the headache side in ≥5 migraine attacks per month patients compared to control group.

Serotonergic mechanisms in the migraine brain - a systematic review

Background Migraine is one of the most common and disabling of all medical conditions, affecting 16% of the general population, causing huge socioeconomic costs globally. Current available treatment options are inadequate. Serotonin is a key molecule in the neurobiology of migraine, but the exact role of brain serotonergic mechanisms remains a matter of controversy. Methods We systematically searched PubMed for studies investigating the serotonergic system in the migraine brain by either molecular neuroimaging or electrophysiological methods. Results The literature search resulted in 59 papers, of which 13 were eligible for review. The reviewed papers collectively support the notion that migraine patients have alterations in serotonergic neurotransmission. Most likely, migraine patients have a low cerebral serotonin level between attacks, which elevates during a migraine attack. Conclusion This review suggests that novel methods of investigating the serotonergic system in the migraine brain are warranted. Uncovering the serotonergic mechanisms in migraine pathophysiology could prove useful for the development of future migraine drugs.

Alcohol-induced headaches: Evidence for a central mechanism?

Alcoholic drinks (ADs) have been reported as a migraine trigger in about one-third of the migraine patients in retrospective studies. Some studies found that ADs trigger also other primary headaches. The studies concerning the role of ADs in triggering various types of primary headaches published after the International Headache Society classification criteria of 1988 were reviewed, and the pathophysiological mechanisms were discussed. Many studies show that ADs are a trigger of migraine without aura (MO), migraine with aura (MA), cluster headache (CH), and tension-type headache (TH). While data on MO and CH are well delineated, those in MA and TH are discordant. There are sparse reports that ADs are also triggers of less frequent types of primary headache such as familial hemiplegic migraine, hemicrania continua, and paroxysmal hemicrania. However, in some countries, the occurrence of alcohol as headache trigger is negligible, perhaps determined by alcohol habits. The frequency estimates vary widely based on the study approach and population. In fact, prospective studies report a limited importance of ADs as migraine trigger. If ADs are capable of triggering practically all primary headaches, they should act at a common pathogenetic level. The mechanisms of alcohol-provoking headache were discussed in relationship to the principal pathogenetic theories of primary headaches. The conclusion was that vasodilatation is hardly compatible with ADs trigger activity of all primary headaches and a common pathogenetic mechanism at cortical, or more likely at subcortical/brainstem, level is more plausible.

Meningeal blood flow is controlled by H2 S-NO crosstalk activating a HNO-TRPA1-CGRP signalling pathway

BACKGROUND AND PURPOSE

Meningeal blood flow is controlled by CGRP released from trigeminal afferents and NO mainly produced in arterial endothelium. The vasodilator effect of NO may be due to the NO-derived compound, nitroxyl (HNO), generated through reaction with endogenous H2 S. We investigated the involvement of HNO in CGRP release and meningeal blood flow.

EXPERIMENTAL APPROACH

Blood flow in exposed dura mater of rats was recorded by laser Doppler flowmetry. CGRP release from the dura mater in the hemisected rat head was quantified using an elisa. NO and H2 S were localized histochemically with specific sensors.

KEY RESULTS

Topical administration of the NO donor diethylamine-NONOate increased meningeal blood flow by 30%. Pretreatment with oxamic acid, an inhibitor of H2 S synthesis, reduced this effect. Administration of Na2 S increased blood flow by 20%, an effect abolished by the CGRP receptor antagonist CGRP8-37 or the TRPA1 channel antagonist HC030031 and reduced when endogenous NO synthesis was blocked. Na2 S dose-dependently increased CGRP release two- to threefold. Co-administration of diethylamine-NONOate facilitated CGRP release, while inhibition of endogenous NO or H2 S synthesis lowered basal CGRP release. NO and H2 S were mainly localized in arterial vessels, HNO additionally in nerve fibre bundles. HNO staining was lost after treatment with L-NMMA and oxamic acid.

CONCLUSIONS AND IMPLICATIONS

NO and H2 S cooperatively increased meningeal blood flow by forming HNO, which activated TRPA1 cation channels in trigeminal fibres, inducing CGRP release. This HNO-TRPA1-CGRP signalling pathway may be relevant to the pathophysiology of headaches.

Choroidal thickness changes in patients with migraine

This observational study evaluated choroidal thickness using spectral domain optical coherence tomography (SD-OCT) in patients with migraine and compared the results with healthy controls. The study population consisted of 42 migraine patients (36 females and 6 males) who were referred from neurology clinics and 42 controls (36 female and 6 male) with no systemic or ocular disease and no headache of any type. All 84 patients underwent complete ophthalmic examination as well as determination of choroidal thickness using a high-speed, high-resolution SD-OCT device (λ = 840 nm, 27.000 A-scans/s, 5-µm axial resolution). The migraine patients were classified into the migraine with aura group or the migraine without aura group, and a pain score from 1 to 10 was determined for each patient based on the Visual Analogue Scale (VAS). The mean choroidal thicknesses were 276.81 ± 37.76 µm in the migraine group and 300.44 ± 24.93 µm in controls. The difference in choroidal thickness between the migraine patients and the controls was significant (P = 0.001). Choroidal thickness measurements of five patients during an attack showed an acute decrease (mean 45.50 µm) in choroidal thickness from the values in the same patients during the attack-free period. There was no correlation between VAS score and the type of migraine with choroidal thickness (P > 0.05). The decrease in mean choroidal thickness in patients with migraine compared to controls may be related to the vascular pathology of the migraine. The acute decrease in choroidal thickness during an attack also lends support to this hypothesis of reduced ocular blood flow in these patients.

Meningeal afferent signaling and the pathophysiology of migraine

Migraine is the most common neurological disorder. Attacks are complex and consist of multiple phases but are most commonly characterized by intense, unilateral, throbbing headache. The pathophysiology contributing to migraine is poorly understood and the disorder is not well managed with currently available therapeutics, often rendering patients disabled during attacks. The mechanisms most likely to contribute to the pain phase of migraine require activation of trigeminal afferent signaling from the cranial meninges and subsequent relay of nociceptive information into the central nervous system in a region of the dorsal brainstem known as the trigeminal nucleus caudalis. Events leading to activation of meningeal afferents are unclear, but nerve endings within this tissue are mechanosensitive and also express a variety of ion channels including acid-sensing ion channels and transient receptor-potential channels. These properties may provide clues into the pathophysiology of migraine by suggesting that decreased extracellular pH and environmental irritant exposure in the meninges contributes to headache. Neuroplasticity is also likely to play a role in migraine given that attacks are triggered by routine events that are typically nonnoxious in healthy patients and clear evidence of sensitization occurs during an attack. Where and how plasticity develops is also not clear but may include events directly on the afferents and/or within the TNC. Among the mediators potentially contributing to plasticity, calcitonin gene-related peptide has received the most attention within the migraine field but other mechanisms may also contribute. Ultimately, greater understanding of the molecules and mechanisms contributing to migraine will undoubtedly lead to better therapeutics and relief for the large number of patients across the globe who suffer from this highly disabling neurological disorder.

Evaluation of Choroidal Thickness Using Spectral-Domain Optical Coherence Tomography in Patients with Migraine: A Comparative Study

Purpose

To assess choroidal thickness in patients with migraine and compare them with healthy controls, using spectral-domain optical coherence tomography (OCT).

Methods

In this prospective case-control study, choroidal thicknesses of 20 newly diagnosed migraine patients and 20 age- and sex-matched healthy subjects were measured using a high-speed, high-resolution frequency domain (FD) OCT device (λ = 840 nm, 26.000 A-scans/s, 5 µm axial resolution). All patients underwent a complete ophthalmic examination before the measurements. OCT measurements were taken at the same time of day (9:00 AM), in order to minimize the effects of diurnal variation.

Results

There was a statistically significant difference in median choroidal thickness between the migraine patients (277.00 [interquartile range (IQR) 85.75] µm) and controls (301.00 [IQR 90.50] µm) (p = 0.012). There were significant differences at all measurement points (p<0.05 for all).

Conclusions

The decreased choroidal thickness of patients with migraine might be related to the vascular pathology of the disease. Further studies are needed to evaluate the etiopathologic relationship between choroidal thickness and migraine.

Increased risk of urinary calculi in patients with migraine: a nationwide cohort study

OBJECTIVE

Whether migraine is associated with urinary calculi is an unresolved issue, although topiramate, a migraine-preventive agent, is known to contribute to this complication. This study investigates the association between migraine and the risk of urinary calculi.

METHODS

We identified a total of 147,399 patients aged ≥18 years with migraine diagnoses recorded in the Taiwan National Health Insurance Research Database between 2005 and 2009. Each patient was randomly matched with one individual without headache using propensity scores. All participants were followed from the date of enrollment until urinary calculi development, death, or the end of 2010.

RESULTS

The risk of urinary calculi was greater in the migraine than the control cohort (adjusted hazard ratio (aHR), 1.58; 95% confidence interval (CI), 1.52-1.63; p < 0.001, irrespective of the influence of topiramate. The risk was higher in younger and female patients. The magnitude of the risk was proportional to the annual frequency of clinic visits for headache (≥6 vs. <3, aHR = 1.11; 95% CI, 1.04-1.17; p = 0.002), but did not differ between migraine patients with and without aura.

CONCLUSIONS

Our study showed migraine was associated with an increased risk of urinary calculi, independent of topiramate use. A higher frequency of clinic visits was associated with a greater risk.

Evaluation of choroidal thickness using spectral-domain optical coherence tomography in migraine patients during acute migraine attacks: a comparative study

PURPOSE

The purpose of this study was to assess choroidal thickness in migraine patients during acute migraine attacks and compare them with healthy controls, using spectral domain optical coherence tomography (OCT).

PATIENTS AND METHODS

In this prospective case-control study, choroidal thicknesses of 46 migraine patients during acute migraine attacks and 46 age- and sex-matched healthy subjects were measured using a high-speed, high-resolution frequency domain-OCT device. All patients underwent a complete ophthalmic examination before the measurements. OCT measurements were taken at the same time of day (0900 hours), in order to minimize the effects of diurnal variation.

RESULTS

There was a statistically significant difference in mean choroidal thickness between the migraine patients during acute migraine attacks (356.3±21.46 μm) and the controls (302.3±18.34 μm; P=0.000). There were significant differences at all measurement points (P<0.001 for all).

CONCLUSION

The increased choroidal thickness of the migraine patients during acute migraine attacks might be related to the vascular pathology of the disease. Further studies are needed to evaluate the etiopathologic relationship between choroidal thickness and acute migraine attack.

[A causative role of vasodilation in migraine? No]

INTRODUCTION

The hypothesis that migraine pain is caused by vasodilation has been challenged by clinical and experimental evidence.

STATE OF ART

The most convincing arguments against the vascular hypothesis come from neuroimaging data. Magnetic resonance imaging studies show that spontaneous migraine attacks are not accompanied by extracranial vasodilation, and by only slight dilation of the intracranial arteries. Pharmacologically-induced migraine attacks also provide further evidence against the role of vasodilation in migraine. Vasodilators such as sildenafil and nitroglycerine trigger attacks without dilation of the middle cerebral artery diameter, whereas VIP (vasoactive intestinal peptide) markedly dilates intra- and extracranial arteries but does not induce migraine attacks. Clinical studies also show a lack of correspondence between the subjective experience of throbbing headache and the arterial pulse. Moreover, many acute anti-migraine agents are not vasoconstrictors.

PERSPECTIVES

Further studies are necessary to clarify the mechanisms of migraine headache generation.

CONCLUSIONS

Contrary to a longstanding and widespread belief, vasodilatation is neither sufficient nor necessary to cause migraine headache and is probably an epiphenomenon.

Migraine in gulf war illness and chronic fatigue syndrome: prevalence, potential mechanisms, and evaluation

Objective: To assess the prevalence of headache subtypes in Gulf War Illness (GWI) and Chronic Fatigue Syndrome (CFS) compared to controls.

Background: Approximately, 25% of the military personnel who served in the 1990–1991 Persian Gulf War have developed GWI. Symptoms of GWI and CFS have considerable overlap, including headache complaints. Migraines are reported in CFS. The type and prevalence of headaches in GWI have not been adequately assessed.

Methods: 50 GWI, 39 CFS and 45 controls had structured headache evaluations based on the 2004 International Headache Society criteria. All subjects had history and physical examinations, fatigue and symptom related questionnaires, measurements of systemic hyperalgesia (dolorimetry), and assessments for exclusionary conditions.

Results: Migraines were detected in 64% of GWI (odds ratio = 11.6 [4.1–32.5]) (mean [±95% CI]) and 82% of CFS subjects (odds ratio = 22.5 [7.8–64.8]) compared to only 13% of controls. There was a predominance of females in the CFS compared to GWI and controls. However, migraine status was independent of gender in GWI and CFS groups (x² = 2.7; P = 0.101). Measures of fatigue, pain, and other ancillary criteria were comparable between GWI and CFS subjects with and without headache.

Conclusion: The high prevalence of migraine in CFS was confirmed and extended to GWI subjects. GWI and CFS may share dysfunctional central pathophysiological pathways that contribute to migraine and subjective symptoms. The high migraine prevalence warrants the inclusion of a structured headache evaluation in GWI and CFS subjects, and treatment when present.

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

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

A PEPTIDE UNCOUPLING CRMP-2 FROM THE PRESYNAPTIC Ca(2+) CHANNEL COMPLEX DEMONSTRATES EFFICACY IN ANIMAL MODELS OF MIGRAINE AND AIDS THERAPY-INDUCED NEUROPATHY

Biological, genetic, and clinical data provide compelling proof for N-type voltage-gated calcium channels (CaV2.2) as therapeutic targets for chronic pain. While decreasing channel function is ultimately anti-nociceptive, directly targeting the channel can lead to multiple adverse effects. Targeting regulators of channel activity may facilitate improved analgesic properties associated with channel block and afford a broader therapeutic window. Towards this end, we recently identified a short peptide, designated CBD3, derived from collapsin response mediator protein 2 (CRMP-2) that suppressed inflammatory and neuropathic hypersensitivity by inhibiting CRMP-2 binding to CaV2.2 [Brittain et al., Nature Medicine 17:822-829 (2011)]. Rodents administered CBD3 intraperitoneally, fused to the HIV TAT protein cell penetrating domain, exhibited antinociception lasting ~4 hours highlighting potential instability, limited oral bioavailability, and/or rapid elimination of peptide. This report focuses on improving upon the parental CBD3 peptide. Using SPOTScan analysis of synthetic versions of the parental CBD3 peptide, we identified peptides harboring single amino acid mutations that bound with greater affinity to CaV2.2. One such peptide, harboring a phenylalanine instead of glycine (G14F), was tested in rodent models of migraine and neuropathic pain. In vivo laser Doppler blood flowmetry measure of capsaicin-induced meningeal vascular responses related to headache pain was almost completely suppressed by dural application of the G14F peptide. The G14F mutant peptide, administered intraperitoneally, also exhibited greater antinociception in Stavudine (2'-3'-didehydro-2'-3'-dideoxythymidine (d4T)/Zerit®) model of AIDS therapy-induced peripheral neuropathy compared to the parent CBD3 peptide. These results demonstrate the patent translational value of small biologic drugs targeting CaV2.2 for management of clinical pain.

The role of nitric oxide in orofacial pain

Nitric oxide (NO) is a free radical gas that has been shown to be produced by nitric oxide synthase (NOS) in different cell types and recognized to act as a neurotransmitter or neuromodulator in the nervous system. NOS isoforms are expressed and/or can be induced in the related structures of trigeminal nerve system, in which the regulation of NOS biosynthesis at different levels of gene expression may allow for a fine control of NO production. Several lines of evidence suggest that NO may play a role through multiple mechanisms in orofacial pain processing. This report will review the latest evidence for the role of NO involved in orofacial pain and the potential cellular mechanisms are also discussed.

Migraine is a neuronal disease

Migraine is a common, paroxysmal, highly disabling primary headache disorder with a genetic background. The primary cause and the origin of migraine attacks are enigmatic. Numerous clinical and experimental results suggest that activation of the trigeminal system (TS) is crucial in its pathogenesis, but the primary cause of this activation is not fully understood. Since activation of the peripheral and central arms of the TS might be related to cortical spreading depression and to the activity of distinct brainstem nuclei (e.g. the periaqueductal grey), we conclude that migraine can be explained as an altered function of the neuronal elements of the TS, the brainstem, and the cortex, the centre of this process comprising activation of the TS. In light of our findings and the literature data, therefore, we can assume that migraine is mainly a neuronal disease.

Headache associated with moyamoya disease: a case story and literature review

Headache associated with moyamoya disease (HAMD) is common in moyamoya disease. However, the characteristics and classification of HAMD are largely unknown. We present a case of a 39-year-old woman with HAMD. To characterize and classify the features of this syndrome, the patient was asked to complete a 4-month diagnostic headache diary. There was a total of 15 ictal days. All episodes were without aura. The headache was more commonly pressing (10/15), mild to moderate in severity (14/15), unchanged by physical activity (11/15), and associated with photophobia (10/15). The International Headache Society Classification was utilized to determine that eight episodes met criteria for probable migraine without aura, while seven episodes met criteria for probable frequent episodic tension-type headache. We identified four other case reports of HAMD with partial descriptions of the characteristics. When combined with our patient, the median age was 34 years old (range 6-49, SD 16). Four were female, while the patient with cluster headache was male. The median time from headache onset to diagnosis with moyamoya disease was 9.5 months (range 0-192, SD 88.0). Headaches were described as migraine with aura in two of five cases, hemiplegic migraine in one of five, and cluster headache in one of five. The highest intensity was described as severe in three of three cases, in which headache intensity was reported. Meanwhile, nausea, vomiting, and photophobia were present in two of three cases, where these features were reported, while nausea without vomiting was seen in one of three cases. In all five cases, patients had other neurological symptoms, such as paresis, seizures, visual disturbances, dysarthria, allodynia, ptosis, and unilateral restless leg syndrome. In conclusion, HAMD can present as migraine without aura. It can be the first presenting symptom of moyamoya disease. The headache features are not diagnostic; hence, early neurovascular imaging should be considered in patients with new onset, refractory migraine-like headache, especially in the setting of other neurological symptoms to exclude underlying moyamoya disease. Further reports using headache diaries are needed to better characterize HAMD as well as to determine whether headache with tension-type features is also part of this condition.