The Journal of Headache and Pain

The diagnosis of migraine is mainly clinical and self-reported, which makes additional examinations unnecessary in most cases. Migraine can be subtyped into chronic (CM) and episodic (EM). Despite the very high prevalence of migraine, there are no evidence-based guidelines for differentiating between these subtypes other than the number of days of migraine headache per month. Thus, we consider it timely to perform a systematic review to search for physiological evidence from functional activity (as opposed to anatomical structure) for the differentiation between CM and EM, as well as potential functional biomarkers. For this purpose, Web of Science (WoS), Scopus, and PubMed databases were screened. Among the 24 studies included in this review, most of them (22) reported statistically significant differences between the groups of CM and EM. This finding is consistent regardless of brain activity acquisition modality, ictal stage, and recording condition for a wide variety of analyses. That speaks for a supramodal and domain-general differences between CM and EM that goes beyond a differentiation based on the days of migraine per month. Together, the reviewed studies demonstrates that electro- and magneto-physiological brain activity (M/EEG), as well as neurovascular and metabolic recordings from functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), show characteristic patterns that allow to differentiate between CM and EM groups. Although a clear brain activity-based biomarker has not yet been identified to distinguish these subtypes of migraine, research is approaching headache specialists to a migraine diagnosis based not only on symptoms and signs reported by patients. Future studies based on M/EEG should pay special attention to the brain activity in medium and fast frequency bands, mainly the beta band. On the other hand, fMRI and PET studies should focus on neural circuits and regions related to pain and emotional processing.

Migraine affects a significant fraction of the world population, yet its etiology is not completely understood. In vitro results highlighted thalamocortical and intra-cortical glutamatergic synaptic gain-of-function associated with a monogenic form of migraine (familial-hemiplegic-migraine-type-1: FHM1). However, how these alterations reverberate on cortical activity remains unclear. As altered responsivity to visual stimuli and abnormal processing of visual sensory information are common hallmarks of migraine, herein we investigated the effects of FHM1-driven synaptic alterations in the visual cortex of awake mice. We recorded extracellular field potentials from the primary visual cortex (V1) of head-fixed awake FHM1 knock-in (n = 12) and wild type (n = 12) mice in response to square-wave gratings with different visual contrasts. Additionally, we reproduced in silico the obtained experimental results with a novel spiking neurons network model of mouse V1, by implementing in the model both the synaptic alterations characterizing the FHM1 genetic mouse model adopted. FHM1 mice displayed similar amplitude but slower temporal evolution of visual evoked potentials. Visual contrast stimuli induced a lower increase of multi-unit activity in FHM1 mice, while the amount of information content about contrast level remained, however, similar to WT. Spectral analysis of the local field potentials revealed an increase in the β/low γ range of WT mice following the abrupt reversal of contrast gratings. Such frequency range transitioned to the high γ range in FHM1 mice. Despite this change in the encoding channel, these oscillations preserved the amount of information conveyed about visual contrast. The computational model showed how these network effects may arise from a combination of changes in thalamocortical and intra-cortical synaptic transmission, with the former inducing a lower cortical activity and the latter inducing the higher frequencies ɣ oscillations. Contrast-driven ɣ modulation in V1 activity occurs at a much higher frequency in FHM1. This is likely to play a role in the altered processing of visual information. Computational studies suggest that this shift is specifically due to enhanced cortical excitatory transmission. Our network model can help to shed light on the relationship between cellular and network levels of migraine neural alterations.

Monoclonal antibodies (mAbs) towards CGRP or the CGRP receptor show good prophylactic antimigraine efficacy. However, their site of action is still elusive. Due to lack of passage of mAbs across the blood-brain barrier the trigeminal system has been suggested a possible site of action because it lacks blood-brain barrier and hence is available to circulating molecules. The trigeminal ganglion (TG) harbors two types of neurons; half of which store CGRP and the rest that express CGRP receptor elements (CLR/RAMP1). With specific immunohistochemistry methods, we demonstrated the localization of CGRP, CLR, RAMP1, and their locations related to expression of the paranodal marker contactin-associated protein 1 (CASPR). Furthermore, we studied functional CGRP release separately from the neuron soma and the part with only nerve fibers of the trigeminal ganglion, using an enzyme-linked immunosorbent assay. Antibodies towards CGRP and CLR/RAMP1 bind to two different populations of neurons in the TG and are found in the C- and the myelinated Aδ-fibers, respectively, within the dura mater and in trigeminal ganglion (TG). CASPR staining revealed paranodal areas of the different myelinated fibers inhabiting the TG and dura mater. Double immunostaining with CASPR and RAMP1 or the functional CGRP receptor antibody (AA58) revealed co-localization of the two peptides in the paranodal region which suggests the presence of the CGRP-receptor. Double immunostaining with CGRP and CASPR revealed that thin C-fibers have CGRP-positive boutons which often localize in close proximity to the nodal areas of the CGRP-receptor positive Aδ-fibers. These boutons are pearl-like synaptic structures, and we show CGRP release from fibers dissociated from their neuronal bodies. In addition, we found that adjacent to the CGRP receptor localization in the node of Ranvier there was PKA immunoreactivity (kinase stimulated by cAMP), providing structural possibility to modify conduction activity within the Aδ-fibers. We observed a close relationship between the CGRP containing C-fibers and the Aδ-fibers containing the CGRP-receptor elements, suggesting a point of axon-axon interaction for the released CGRP and a site of action for gepants and the novel mAbs to alleviate migraine.

Migraine is a paroxysmal, disabling primary headache that affects 16 % of the adult population. In spite of decades of intense research, the origin and the pathophysiology mechanisms involved are still not fully known. Although triptans and gepants provide effective relief from acute migraine for many patients, their site of action remains unidentified. It has been suggested that during migraine attacks the leakiness of the blood-brain barrier (BBB) is altered, increasing the passage of anti-migraine drugs. This study aimed to investigate the effect of experimental inflammation, following dural application of complete Freund’s adjuvant (CFA) or inflammatory soup (IS) on brain and trigeminal microvascular passage. In order to address this issue, we induced local inflammation in male Sprague-Dawley-rats dura mater by the addition of CFA or IS directly on the dural surface. Following 2, 24 or 48 h of inflammation we calculated permeability-surface area product (PS) for [51Cr]-EDTA in the trigeminal ganglion (TG), spinal trigeminal nucleus, cortex, periaqueductal grey and cerebellum. We observed that [51Cr]-EDTA did not pass into the central nervous system (CNS) in a major way. However, [51Cr]-EDTA readily passed the TG by >30 times compared to the CNS. Application of CFA or IS did not show altered transfer constants. With these experiments we show that dural IS/CFA triggered TG inflammation, did not increase the BBB passage, and that the TG is readily exposed to circulating molecules. The TG could provide a site of anti-migraine drug interaction with effect on the trigeminal system.

The premonitory stage of migraine attacks, when symptomatology outside of pain can manifest hours to days before the onset of the headache, is well recognised. Such symptoms have been reported in adults in a number of studies, and have value in predicting an impending headache. These symptoms have not been extensively studied in children. We aimed to characterise which, if any, of these symptoms are reported in children seen within a Specialist Headache Service. We reviewed clinic letters from the initial consultation of children and adolescents seen within the Specialist Headache Service at Great Ormond Street Hospital between 1999 and 2015 with migraine in whom we had prospectively assessed clinical phenotype data. We randomly selected 100 cases with at least one premonitory symptom recorded in the letter. For these patients, the age at headache onset, presence of family history of headache, headache diagnosis, presence of episodic syndromes which may be associated with headache, developmental milestones, gestation at birth, mode of delivery and presence of premonitory symptoms occurring before or during headache were recorded. Of the 100 patients selected, 65 % were female. The age range of the patients was 18 months to 15 years at the time of headache onset. The most common diagnosis was chronic migraine in 58 %, followed by episodic migraine (29 %), New Daily Persistent Headache with migrainous features (8 %) and hemiplegic migraine (5 %). A history of infantile colic was noted in 31 % and was the most common childhood episodic syndrome associated with migraine. The most common premonitory symptoms recorded were fatigue, mood change and neck stiffness. The commonest number of reported premonitory symptoms was two. Premonitory symptoms associated with migraine are reported in children as young as 18 months, with an overall clinical phenotype comparable to adults. Better documentation of this stage will aid parents and clinicians to better understand the phenotype of attacks, better recognise migraine and thus initiate appropriate management. Larger studies with a broader base are warranted to understand the extent and implications of these symptoms for childhood and adolescent migraine.

In this study, we retrospectively analyzed the relationship between headache recurrence and serotonin 5-HT1B/1D receptor occupancy (Φ1B and Φ1D). Triptans marketed in Japan (sumatriptan, zolmitriptan, eletriptan, rizatriptan, naratriptan) were investigated. Receptor occupancies were calculated from both the pharmacokinetic and pharmacodynamic data of triptans. We examined the relationships between recurrence rate and elimination half-lives, and Ф1B and Ф1D, as calculated from the time-course of plasma drug concentration obtained from other studies. The time until Ф1B and Ф1D became 50 % or less, 40 % or less, and 30 % or less was calculated as duration time to examine the relationship with recurrence rate. For Ф1B, eletriptan remained at a low level. For Ф1D, it was indicated that all triptans obtained an occupancy of 80 % or higher at maximum. For all items, though recurrence tended to be lower along with longer half-life, no significant statistical correlation was found. For both Ф1B and Ф1D, the recurrence rate tended to be lower as the duration became longer. In addition, a significant correlation was observed for Ф1D (p < 0.05). For clarifying the Ф value and time period most closely correlated with recurrence rate, recurrence and Ф1B and Ф1D at 6, 12, and 18 h after administration were calculated. The most significant correlation was observed between recurrence rate and Ф1D at 12 h after administration (p < 0.01). As an index for evaluating headache recurrence following triptan administration, recurrence rate and Ф1D value at 12 h after administration were found to be most closely correlated and useful for analysis. Our results indicate that headache recurrence inhibition can be evaluated using these values.

Patients with chronic daily headache (CDH) are difficult to treat. A combination of general measures and specific pharmacological treatments is necessary. When possible, pharmacological management should be planned on an outpatient basis. The general protocol should include abrupt discontinuation of the offending symptomatic medications, specific treatment for detoxification, daily nonsteroidal anti-inflammatory drugs (NSAIDs) for about 1 month, triptans only for moderate-severe headache, and prophylactic treatment. Either amitriptyline plus propranolol or valproic acid have been classically recommended for transformed migraine prophylaxis. Refractory patients can respond to a combination of a beta-blocker and valproic acid, possibly due to their complementary mechanisms of action. Recently, the new antiepileptic topiramate has been shown to be especially useful in this indication. At least one-third of patients, however, do not improve. Therefore, the best treatment of this incapacitating entity continues to be its prevention. Preventive measures should include: (1) public information concerning the risk of frequent self-treatment for headaches; (2) inform headache patients of the risk of analgesic overuse/rebound headache; (3) recommend NSAIDs and triptans as symptomatic medications; and (4) active use of preventive medications when headaches begin to increase in frequency.

GABA and glutamic acid are the main inhibitory and excitatory neurotransmitters of central nervous system. Among other functions they modulate the pain threshold in the CNS. For this reason it has been hypothesized that anomalies of GABA and glutamate turn–over may play a role in migraine pathogenesis. In this review are discussed the evidences in favour of this hypothesis. A derangement of GABA may be an important factor in the occurrence of migraine attacks and their recurrence, whereas high level of glutamic acid may represent a biochemical marker of the neuronal hyperexcitability that may be the underlying cause of the aura. The pharmacological modulation of metabolism of both neurotransmitters is a promising approach to improve migraine therapy. In particular the studies presented here suggest that gabaergic drugs may be useful in migraine without aura, antiglutamatergic drugs are indicated to treat migraine with aura.

The first manuscript in this series delineated a model of structured headache services, potentially cost-effective but requiring formal cost-effectiveness analysis (CEA). We envisaged a need for a new outcome measure for this purpose, applicable to all forms of treatment, care and care-delivery systems as opposed to comparisons of single-modality treatments. A literature review confirmed the lack of any suitable established measure. We prioritised construct validity, simplicity, comprehensiveness and expression in intuitive units. We noted that pain was the key burdensome symptom of migraine and episodic tension-type headache (TTH), that pain above a certain level was disabling, that it was difficult to put economic value to pain but relatively easy to do this for time, a casualty of headache leading to lost productivity. Alleviation of pain to a non-disabling level would be expected to bring restoration of function. We therefore based the measure on time spent in the ictal state (TIS) of migraine or TTH, either as total TIS or proportion of all time. We expressed impact on health, in units of time, as TIS*DW, where DW was the disability weight for the ictal state supplied by the Global Burden of Disease (GBD) studies. If the time unit was hours, TIS*DW yielded hours lived with (or lost to) disability (HLDs), in analogy with GBD’s years lived with disability (YLDs). Acute treatments would reduce TIS by shortening attack duration, preventative treatments by reducing attack frequency; health-care systems such as structured headache services would have these effects by delivering these treatments. These benefits were all measurable as HLDs-averted. Population-level estimates would be derived by factoring in prevalence, but also taking treatment coverage and adherence into account. For health-care systems, additional gains from provider-training (promoting adherence to guidelines and, therefore, enhancing coverage) and consumer-education (improving adherence to care plans), increasing numbers within populations gaining the benefits of treatments, would be measurable by the same metric. The new outcome measure expressed in intuitive units of time is applicable to treatments of all modalities and to system-level interventions for multiple headache types, with utility for CEA and for informing health policy.