HCN2 Ion Channels Drive Pain in Rodent Models of Migraine.

Migraine is believed to be initiated by neuronal activity in the CNS, that triggers excitation of nociceptive trigeminal ganglion (TG) nerve fibers innervating the meninges and thus causes a unilateral throbbing headache. Drugs that precipitate or potentiate migraine are known to elevate intracellular levels of the cyclic nucleotides cAMP or cGMP, while anti-migraine treatments couple to signaling pathways that reduce cAMP or cGMP, suggesting an involvement of these cyclic nucleotides in migraine. Members of the HCN ion channel family are activated by direct binding of cAMP or cGMP, suggesting in turn that a member of this family may be a critical trigger of migraine. Here, we show that pharmacological block or targeted genetic deletion of HCN2 abolishes migraine-like pain in three rodent migraine models (in both sexes). Induction of migraine-like pain in these models triggered expression of the protein C-FOS, a marker of neuronal activity, in neurons of the trigeminocervical complex (TCC), where TG neurons terminate, and C-FOS expression was reversed by peripheral HCN2 inhibition. HCN2 block in vivo inhibited both evoked and spontaneous neuronal activity in nociceptive TG neurons. The NO donor glyceryl trinitrate (GTN) caused an increase in cGMP in the TG in vivo Exposing isolated TG neurons to GTN caused a rightward shift in the voltage dependence of HCN currents and thus increased neuronal excitability. This work identifies HCN2 as a novel target for the development of migraine treatments.SIGNIFICANCE STATEMENT Migraine is believed to be initiated by localized excitability of neurons within the CNS, but the most disturbing symptom, the characteristic throbbing migraine headache pain, is widely agreed to be caused by activity in afferent pain-sensitive (nociceptive) nerve fibers of the trigeminal nerve. Using a variety of preclinical models of migraine, we identify the HCN2 ion channel as the molecular source of trigeminal hyperexcitability in migraine and we show that pharmacological or genetic inhibition of HCN2 can relieve migraine-like pain symptoms. The work highlights the HCN2 ion channel as a potential pharmacological target for the development of novel analgesics effective in migraine.

The increasing role of electronic media in headache.

Most individuals with access to the internet use social media platforms. These platforms represent an excellent opportunity to disseminate knowledge about management and treatment to the benefit of patients. The International Headache Society, The European Headache Federation, and The American Headache Society have electronic media committees to promote and highlight the organizations' expertise and disseminate research findings. A growing mistrust in science has made dealing with infodemics (i.e., sudden access to excessive unvetted information) an increasing part of clinical management. An increasing role of these committees will be to address this challenge. As an example, recent studies have demonstrated that the most popular online content on migraine management is not evidence-based and is disseminated by for-profit organizations. As healthcare professionals and members of professional headache organizations, we are obliged to prioritize knowledge dissemination. A progressive social media strategy is associated not only with increased online visibility and outreach, but also with a higher scientific interest. To identify gaps and barriers, future research should assess the range of available information on headache disorders in electronic media, characterize direct and indirect consequences on clinical management, and recognize best practice and strategies to improve our communication on internet-based communication platforms. In turn, these efforts will reduce the burden of headache disorders by facilitating improved education of both patients and providers.

Two-year effectiveness of erenumab in resistant chronic migraine: a prospective real-world analysis.

BACKGROUND: Controlled and real-world evidence have demonstrated the efficacy of calcitonin gene related peptide (CGRP) monoclonal antibodies (MABs) in migraine. However, data on the over-one-year sustained effectiveness of CGRP MABs in resistant chronic migraine (CM) is sparse.  METHODS: This is a two-year real-world prospective analysis of an ongoing single centre audit conducted in patients with resistant CM. Patients received monthly erenumab for six months before assessing its effectiveness. Responders were considered those who achieved at least 30% reduction in monthly migraine days (MMD) by month 6, compared to baseline. Secondary outcomes were also analysed, including changes of the Headache Impact Test version 6 (HIT-6). RESULTS: One hundred sixty-four patients [135 (82.3%) females; mean age 46 SD 14) years] were included in the audit and 160 patients analysed. Patients had failed a mean of 8.4 preventive treatments at baseline. At month 6, 76 patients (48%) were 30% responders to erenumab, 50 patients (31%) were 50% responders and 25 (15%) were 75% responders. The mean reduction in MMD at month 6 was 7.5 days compared to baseline (P < 0.001). At month 12 and month 18, 61 patients (38%) and 52 patients (33%) remained 30% responders respectively. At month 24, 36 patients (23%) remained 30% responders, 25 patients (16%) and 13 patients (8%) were respectively 50% and 75% responders. Compared to 95% of patients at baseline, at months 6, 12 and 24, 46%, 29% and 16% of responders respectively had severe disability. At least one adverse event at month 6, 12, 18 and 24 was reported by 49%, 19%, 11% and 3% of patients. By month 6, 13% of patients discontinued the treatment because of side effects, often constipation. CONCLUSIONS: Long-term sustained effectiveness of erenumab was reported only by a minority of resistant CM patients. Although more research in resistant migraine is needed, Erenumab can provide long-term meaningful reduction in migraine load and migraine-related disability in some patients.

Comparing the relative and absolute effect of erenumab: is a 50% response enough? Results from the ESTEEMen study.

BACKGROUND: Monoclonal antibodies acting on the calcitonin gene-related peptide (CGRP) or its receptor have changed migraine preventive treatment. Those treatments have led to reconsidering the outcomes of migraine prevention. Available data mostly considered benefits in terms of relative efficacy (percent or absolute decrease in monthly migraine days [MMDs] or headache days compared with baseline). However, not enough attention has been paid to residual MMDs and/or migraine-related disability in treated patients. In the present study, we aimed at comparing the relative and absolute efficacy of erenumab. METHODS: ESTEEMen was a collaborative project among 16 European headache centers which already performed real-life data collections on patients treated with erenumab for at least 12 weeks. For the present study, we performed a subgroup analysis on patients with complete data on MMDs at baseline and at weeks 9-12 of treatment. Starting from efficacy thresholds proposed by previous literature, we classified patients into 0-29%, 30-49%, 50-74%, and ≥75% responders according to MMD decrease from baseline to weeks 9-12 of treatment. For each response category, we reported the median MMDs and Headache Impact test-6 (HIT-6) scores at baseline and at weeks 9-12. We categorized the number of residual MMDs at weeks 9-12 as follows: 0-3, 4-7, 8-14, ≥15. We classified HIT-6 score into four categories: ≤49, 50-55, 56-59, and ≥60. To keep in line with the original scope of the ESTEEMen study, calculations were performed in men and women. RESULTS: Out of 1215 patients, at weeks 9-12, 381 (31.4%) had a 0-29% response, 186 (15.3%) a 30-49% response, 396 (32.6%) a 50-74% response, and 252 (20.7%) a ≥75% response; 246 patients (20.2%) had 0-3 residual MMDs, 443 (36.5%) had 4-7 MMDs, 299 (24.6%) had 8-14 MMDs, and 227 (18.7%) had ≥15 MMDs. Among patients with 50-74% response, 246 (62.1%) had 4-7 and 94 (23.7%) 8-14 residual MMDs, while among patients with ≥75% response 187 (74.2%) had 0-3 and 65 (25.8%) had 4-7 residual MMDs. CONCLUSIONS: The present study shows that even patients with good relative response to erenumab may have a clinically non-negligible residual migraine burden. Relative measures of efficacy cannot be enough to thoroughly consider the efficacy of migraine prevention.

A prospective real-world analysis of erenumab in refractory chronic migraine.

BACKGROUND: Clinical trials have shown the safety and clinical superiority of erenumab compared to placebo in chronic migraine (CM). The aim of this analysis is to evaluate the effectiveness and tolerability of erenumab in a real-world setting in patients with refractory CM. METHODS: This is a prospective single centre real-world audit conducted in patients with CM with and without medication overuse, refractory to established preventive medications, who received monthly erenumab for 6 months. RESULTS: Of 164 patients treated, 162 patients (female = 135, mean age 46 ± 14.3 years old) were included in the audit. Patients had failed a mean of 8.4 preventive treatments at baseline and 91% of patients failed Botulinum toxin type A at baseline. The mean reduction in monthly migraine days was 6.0 days at month 3 (P = 0.002) and 7.5 days at month 6 (P < 0.001) compared to baseline. The mean reduction in monthly headache days was 6.3 days (P < 0.001) at month 3 and 6.8 days (P < 0.001) at month 6. At month 3, 49%, 35% and 13% and at month 6, 60%, 38% and 22% of patients obtained at least a 30%, 50% and 75% reduction in migraine days, respectively. The percentage of patients with medication overuse was reduced from 54% at baseline to 20% at month 3 and to 25% at month 6. Compared to baseline, the mean reduction of Headache Impact Test-6 score was 7.7 points at month 3 (from 67.6 ± 0.4 to 59.9 ± 0.9) (P < 0.001) and of 7.5 points at month 6 (60.1 ± 1.3) (P = 0.01). The percentage of patients with severe headache-related disability (HIT-6: 60-78) was reduced from 96% at baseline to 68% after three monthly treatments and to 59% after six treatments. At least one side effect was reported by 48% of patients at month 1, 22% at month 3 and 15% at month 6. Constipation (20%) and cold/flu-like symptoms (15%) were the most frequent adverse events reported. CONCLUSION: Erenumab may be an effective and well tolerated therapy for medically refractory CM patients with and without medication overuse.

Mechanisms of migraine as a chronic evolutive condition.

Understanding the mechanisms of migraine remains challenging as migraine is not a static disorder, and even in its episodic form migraine remains an "evolutive" chronic condition. Considerable progress has been made in elucidating the pathophysiological mechanisms of migraine, associated genetic factors that may influence susceptibility to the disease, and functional and anatomical changes during the progression of a migraine attack or the transformation of episodic to chronic migraine. Migraine is a life span neurological disorder that follows an evolutive age-dependent change in its prevalence and even clinical presentations. As a disorder, migraine involves recurrent intense head pain and associated unpleasant symptoms. Migraine attacks evolve over different phases with specific neural mechanisms and symptoms being involved during each phase. In some patients, migraine can be transformed into a chronic form with daily or almost daily headaches. The mechanisms behind this evolutive process remain unknown, but genetic and epigenetic factors, inflammatory processes and central sensitization may play an important role.

Primary headaches during lifespan.

Primary headaches are one of the most prevalent neurological disorders and can occur during a wide range of lifespan. Primary headaches, especially migraine, are cyclic disorders with a complex sequence of symptoms within every headache attack. There is no systematic review of whether these symptoms changes during lifespan. Indeed, the clinical presentation of migraine shows an age-dependent change with a significantly shorter duration of the attacks and occurrence of different paroxysmal symptoms, such as vomiting, abdominal pain or vertigo, in childhood and, in contrast, largely an absence of autonomic signs and a more often bilateral headache in the elderly. The age-dependent differences in the clinical presentation are less distinct in cluster headache and, especially, in tension-type headache. The differences in the clinical presentation are in agreement with the idea that the connectivity of hypothalamic areas with different brainstem areas, especially the central parasympathetic areas, is important for the clinical manifestation of migraine, as well as, the change during lifespan.

Correction to: Primary headaches during lifespan.

Following publication of the original article [1], we have been notified that one of the author names was incompletely presented.

Non-invasive vagus nerve stimulation for the management of refractory primary chronic headaches: A real-world experience.

Background Non-invasive vagus nerve stimulation has initial evidence of efficacy in migraine and cluster headache. However, little is known about its role in the management of refractory chronic headaches. Methods We evaluated the preventive and abortive effects of non-invasive vagus nerve stimulation in 41 consecutive patients with refractory primary chronic headaches in an open-label prospective clinical audit. Headache diaries were used to collect clinical information. Those who obtained at least 30% reduction in headache days/episodes after three months of treatment were considered responders and were offered treatment continuation. Results Twenty-three patients with chronic migraine, 12 with chronic cluster headache, four with hemicrania continua and two with short-lasting unilateral neuralgiform headache attacks with autonomic symptoms (SUNA) were treated. Two of 23 chronic migraine patients, one of 12 chronic cluster headache patients, and two of four hemicrania continua patients were considered responders. None of the patients with SUNA benefited from the therapy. Two chronic migraine patients were able to reduce the pain severity of moderate migraines with non-invasive vagus nerve stimulation. Conclusion Non-invasive vagus nerve stimulation may not constitute an effective acute nor preventive treatment in refractory chronic primary headaches. The encouraging effect in hemicrania continua warrants further evaluation in larger studies.

Emerging drugs for migraine treatment: an update.

Introduction: Migraine is a very frequent and disabling neurological disorder. The current treatment options are old, generally poorly tolerated and not migraine-specific, reflecting the low priority of migraine research and highlighting the vast unmet need in its management. Areas covered: Advancement in the understanding of migraine pathophysiological mechanisms and identification of novel potentially meaningful targets have resulted in a multitude of emerging acute and preventive treatments. Here we review the known putative migraine pathophysiological mechanisms in order to understand the rationale of the most promising novel treatments targeting the Calcitonin-Gene-Related Peptide receptor and ligand and the 5 hydroxytryptamine (5-HT)1F receptor. Key findings on the phase II and phase III clinical trials on these treatments will be summarized. Furthermore, a critical analysis on failed trials of potentially meaningful targets such the nitric oxide and the orexinergic pathways will be conducted. Future perspective will be outlined. Expert opinion: The recent approval of Erenumab and Fremanezumab is a major milestone in the therapy of migraine since the approval of triptans. Several more studies are needed to fully understand the clinical potential, long-term safety and cost-effectiveness of these therapies. This paramount achievement should stimulate the development of further research in the migraine field.

Transcranial magnetic stimulation and potential cortical and trigeminothalamic mechanisms in migraine.

A single pulse of transcranial magnetic stimulation has been shown to be effective for the acute treatment of migraine with and without aura. Here we aimed to investigate the potential mechanisms of action of transcranial magnetic stimulation, using a transcortical approach, in preclinical migraine models. We tested the susceptibility of cortical spreading depression, the experimental correlate of migraine aura, and further evaluated the response of spontaneous and evoked trigeminovascular activity of second order trigemontothalamic and third order thalamocortical neurons in rats. Single pulse transcranial magnetic stimulation significantly inhibited both mechanical and chemically-induced cortical spreading depression when administered immediately post-induction in rats, but not when administered preinduction, and when controlled by a sham stimulation. Additionally transcranial magnetic stimulation significantly inhibited the spontaneous and evoked firing rate of third order thalamocortical projection neurons, but not second order neurons in the trigeminocervical complex, suggesting a potential modulatory effect that may underlie its utility in migraine. In gyrencephalic cat cortices, when administered post-cortical spreading depression, transcranial magnetic stimulation blocked the propagation of cortical spreading depression in two of eight animals. These results are the first to demonstrate that cortical spreading depression can be blocked in vivo using single pulse transcranial magnetic stimulation and further highlight a novel thalamocortical modulatory capacity that may explain the efficacy of magnetic stimulation in the treatment of migraine with and without aura.

Evidence for orexinergic mechanisms in migraine.

OBJECTIVE: To examine the effect of the orexinergic blockade with a dual orexin receptor antagonist (DORA) on experimental models of peripheral and central trigeminal as well as cortical activation relevant to migraine and migraine aura. METHODS: In this study we used a precursor of suvorexant, a dual orexin receptor antagonist #12 (DORA-12) in established experimental in vivo models of dural trigeminovascular nociception in rat. Neurogenic dural vasodilation and electrophysiological recordings of second order trigeminocervical neurons were used to study trigeminal nociceptive mechanisms directly. KCl-evoked cortical spreading depression was also used as a surrogate for migraine aura. RESULTS: Neurogenically-induced vasodilation of the middle meningeal artery, caused by nociceptive activation of peripheral afferent projections of the trigeminal nerve, was attenuated by intravenous DORA-12 (1 mgkg(-1)). Second-order trigeminocervical complex neuronal activity was significantly inhibited by intravenous DORA-12 (1 mgkg(-1)). DORA-12 significantly reduced susceptibility to KCl-evoked cortical spreading depression. CONCLUSION: The study provides the first direct evidence, that simultaneous antagonism on both orexin receptors is able to attenuate trigeminal nociceptive activity as well as to induce an elevation of the threshold for the induction of a cortical spreading depression (CSD). In the clinical context, these data imply that targeting the hypothalamic orexinergic system may offer an entirely novel mechanism for the preventive treatment of migraine with and without aura.

Anandamide produced by Ca(2+)-insensitive enzymes induces excitation in primary sensory neurons.

The endogenous lipid agent N-arachidonoylethanolamine (anandamide), among other effects, has been shown to be involved in nociceptive processing both in the central and peripheral nervous systems. Anandamide is thought to be synthesised by several enzymatic pathways both in a Ca(2+)-sensitive and Ca(2+)-insensitive manner, and rat primary sensory neurons produce anandamide. Here, we show for the first time, that cultured rat primary sensory neurons express at least four of the five known Ca(2+)-insensitive enzymes implicated in the synthesis of anandamide, and that application of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-arachidonoyl, the common substrate of the anandamide-synthesising pathways, results in anandamide production which is not changed by the removal of extracellular Ca(2+). We also show that anandamide, which has been synthesised in primary sensory neurons following the application of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-arachidonoyl induces a transient receptor potential vanilloid type 1 ion channel-mediated excitatory effect that is not inhibited by concomitant activation of the cannabinoid type 1 receptor. Finally, we show that sub-populations of transient receptor potential vanilloid type 1 ion channel-expressing primary sensory neurons also express some of the putative Ca(2+)-insensitive anandamide-synthesising enzymes. Together, these findings indicate that anandamide synthesised by primary sensory neuron via a Ca(2+)-insensitive manner has an excitatory rather than an inhibitory role in primary sensory neurons and that excitation is mediated predominantly through autocrine signalling. Regulation of the activity of the Ca(2+)-insensitive anandamide-synthesising enzymes in these neurons may be capable of regulating the activity of these cells, with potential relevance to controlling nociceptive processing.

Differential trigeminovascular nociceptive responses in the thalamus in the familial hemiplegic migraine 1 knock-in mouse: a Fos protein study.

Familial hemiplegic migraine type 1 (FHM-1) is a monogenic subtype of migraine with aura caused by missense mutations in the CACNA1A gene, which encodes the pore-forming α1 subunit of voltage-gated neuronal CaV2.1 (P/Q-type) calcium channels. Transgenic knock-in mice expressing the CACNA1A R192Q mutation that causes FHM-1 in patients show a greater susceptibility to cortical spreading depression, the likely underlying mechanism of typical human migraine aura. The aim of this study was to compare neuronal activation within the trigeminal pain pathways in response to nociceptive trigeminovascular stimulation in wild-type and R192Q knock-in mice. After sham surgery or electrical stimulation of the superior sagittal sinus for 2h, or stimulation preceded by treatment with naratriptan, mice underwent intracardiac perfusion, and the brain, including the brainstem, was removed. Fos expression was measured in the trigeminocervical complex (TCC) and the lateral (ventroposteromedial, ventrolateral), medial (parafascicular, centromedian) and posterior thalamic nuclei. In the TCC of wild-type animals, the number of Fos-positive cells increased significantly following dural stimulation compared to the sham control group (P<0.001) and decreased after naratriptan treatment (P<0.05). In R192Q knock-in mice, there was no significant difference between the stimulated and sham (P=0.10) or naratriptan pre-treated groups (P=0.15). The number of Fos-positive cells in the R192Q stimulated group was significantly lower compared to the wild-type stimulated mice (P<0.05). In the thalamus, R192Q mice tended to be more sensitive to stimulation compared to the sham control in the medial and posterior nuclei, and between the two strains of stimulated animals there was a significant difference in the centromedian (P<0.005), and posterior nuclei (P<0.05). The present study suggests that the FHM-1 mutation affects more rostral brain structures in this experimental paradigm, which offers a novel perspective on possible differential effects of mutations causing migraine in terms of phenotype-genotype correlations.

Pharmacology of the capsaicin receptor, transient receptor potential vanilloid type-1 ion channel.

The capsaicin receptor, transient receptor potential vanilloid type 1 ion channel (TRPV1), has been identified as a polymodal transducer molecule on a sub-set of primary sensory neurons which responds to various stimuli including noxious heat (> -42 degrees C), protons and vanilloids such as capsaicin, the hot ingredient of chilli peppers. Subsequently, TRPV1 has been found indispensable for the development of burning pain and reflex hyperactivity associated with inflammation of peripheral tissues and viscera, respectively. Therefore, TRPV1 is regarded as a major target for the development of novel agents for the control of pain and visceral hyperreflexia in inflammatory conditions. Initial efforts to introduce agents acting on TRPV1 into clinics have been hampered by unexpected side-effects due to wider than expected expression in various tissues, as well as by the complex pharmacology, of TRPV1. However, it is believed that better understanding of the pharmacological properties of TRPV1 and specific targeting of tissues may eventually lead to the development of clinically useful agents. In order to assist better understanding of TRPV1 pharmacology, here we are giving a comprehensive account on the activation and inactivation mechanisms and the structure-function relationship of TRPV1.

Resistant and refractory migraine: clinical presentation, pathophysiology, and management.

Migraine is a leading cause of disability worldwide. A minority of individuals with migraine develop resistant or refractory conditions characterised by ≥ 8 monthly days of debilitating headaches and inadequate response, intolerance, or contraindication to ≥3 or all preventive drug classes, respectively. Resistant and refractory migraine are emerging clinical definitions stemming from better knowledge of the pathophysiology of migraine and from the advent of migraine-specific preventive treatments. Resistant migraine mostly results from drug failures, while refractory migraine has complex and still unknown mechanisms that impair the efficacy of preventive treatments. Individuals with resistant migraine can be treated with migraine-specific preventive drugs. The management of refractory migraine is challenging and often unsuccessful, being based on combinations of different drugs and non-pharmacological treatment. Future research should aim to identify individuals at risk of developing treatment failures, prevent the condition, investigate the mechanisms of refractoriness to treatments, and find effective treatment strategies.

Recent Developments in Engineering Non-Paralytic Botulinum Molecules for Therapeutic Applications.

This review discusses the expanding application of botulinum neurotoxin in treating neurological conditions. The article specifically explores novel approaches to using non-paralytic botulinum molecules. These new molecules, such as BiTox or el-iBoNT, offer an alternative for patients who face limitations in using paralytic forms of botulinum neurotoxin due to concerns about muscle function loss. We highlight the research findings that confirm not only the effectiveness of these molecules but also their reduced paralytic effect. We also discuss a potential cause for the diminished paralytic action of these molecules, specifically changes in the spatial parameters of the new botulinum molecules. In summary, this article reviews the current research that enhances our understanding of the application of new botulinum neurotoxins in the context of common conditions and suggests new avenues for developing more efficient molecules.

Reporting Quality and Risk of Bias Analysis of Published RCTs Assessing Anti-CGRP Monoclonal Antibodies in Migraine Prophylaxis: A Systematic Review.

Objective: Phase II/III randomized clinical trials (RCTs) are vulnerable to many types of bias beyond randomization. Insights into the reporting quality of RCTs involving migraine patients treated with monoclonal antibodies targeting the calcitonin gene-related peptide system (anti-CGRP MAbs) are currently lacking. Our aim was to analyze the reporting quality of phase II/III RCTs involving migraine patients treated with anti-CGRP MAbs. Methods: A systematic search was performed on the PubMed and EMBASE databases, according to PRISMA guidelines, for relevant RCTs in either episodic or chronic migraine prevention. Additionally, an adapted version of the 2010 CONSORT statement checklist was utilized. The ROBvis online tool was used to document the risk of bias. Results: From the initially identified 179 articles, we finally found 31 RCTs that were eligible for evaluation. The average CONSORT compliance was 88.7% (69.7-100%), while 93.5% (N = 29) of the articles had a compliance greater than 75%. Twenty-eight CONSORT items were reported in more than 75% of the articles. The average compliance of the analyzed RCTs was 93.9% for Galcanezumab, 91.3% for Fremanezumab, followed by 85.4% for Erenumab and Eptinezumab studies. Implementation of the ROB2 tool showed some concerning "missing information" arising from the inadequate reporting. Specifically, 50% of the studies (N = 16) were categorized as having inadequate information regarding the randomization process. Conclusions: Adequate reporting quality was disclosed in the evaluated RCTs with anti-CGRP MAbs in migraine prevention. However, some methodological issues need to be highlighted to be addressed in future studies assessing the efficacy of new molecules targeting CGRP or other candidate pathways implicated in migraine pathophysiology.

Acid-sensing ion channel 1: a novel therapeutic target for migraine with aura.

OBJECTIVE: Migraine with aura is a severe debilitating neurological disorder with few relatively specific therapeutic options. METHODS: We used amiloride, a blocker of epithelial sodium channels, to evaluate its pharmacological potential and explored the biology of a potential mechanism of action in well-established experimental models. RESULTS: Amiloride was shown to block cortical spreading depression, the experimental correlate of aura, and inhibited trigeminal activation in in vivo migraine models, via an acid-sensing ion channel 1 mechanism. Remarkably, amiloride then demonstrated good clinical efficacy in a small open-labeled pilot study of patients, reducing aura and headache symptoms in 4 of 7 patients with otherwise intractable aura. INTERPRETATION: The observations here identify an entirely novel treatment strategy for migraine.

Assessing the risk of central post-stroke pain of thalamic origin by lesion mapping.

Central post-stroke pain of thalamic origin is an extremely distressing and often refractory disorder. There are no well-established predictors for pain development after thalamic stroke, and the role of different thalamic nuclei is unclear. Here, we used structural magnetic resonance imaging to identify the thalamic nuclei, specifically implicated in the generation of central post-stroke pain of thalamic origin. Lesions of 10 patients with central post-stroke pain of thalamic origin and 10 control patients with thalamic strokes without pain were identified as volumes of interest on magnetic resonance imaging data. Non-linear deformations were estimated to match each image with a high-resolution template and were applied to each volume of interest. By using a digital atlas of the thalamus, we elucidated the involvement of different nuclei with respect to each lesion. Patient and control volumes of interest were summed separately to identify unique areas of involvement. Voxelwise odds ratio maps were calculated to localize the anatomical site where lesions put patients at risk of developing central post-stroke pain of thalamic origin. In the patients with pain, mainly lateral and posterior thalamic nuclei were affected, whereas a more anterior-medial lesion pattern was evident in the controls. The lesions of 9 of 10 pain patients overlapped at the border of the ventral posterior nucleus and the pulvinar, coinciding with the ventrocaudalis portae nucleus. The lesions of this area showed an odds ratio of 81 in favour of developing thalamic pain. The high odds ratio at the ventral posterior nucleus-pulvinar border zone indicates that this area is crucial in the pathogenesis of thalamic pain and demonstrates the feasibility of identifying patients at risk of developing central post-stroke pain of thalamic origin early after thalamic insults. This provides a basis for pre-emptive treatment studies.