Clinical recognition of allodynia in migraine

The role of Toll-like receptors in neuropsychiatric disorders: Immunopathology, treatment, and management

Neuropsychiatric disorders denote a broad range of illnesses involving neurology and psychiatry. These disorders include depressive disorders, anxiety, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, autism spectrum disorders, headaches, and epilepsy. In addition to their main neuropathology that lies in the central nervous system (CNS), lately, studies have highlighted the role of immunity and neuroinflammation in neuropsychiatric disorders. Toll-like receptors (TLRs) are innate receptors that act as a bridge between the innate and adaptive immune systems via adaptor proteins (e.g., MYD88) and downstream elements; TLRs are classified into 13 families that are involved in normal function and illnesses of the CNS. TLRs expression affects the course of neuropsychiatric disorders, and is influenced during their pharmacotherapy; For example, the expression of multiple TLRs is normalized during the major depressive disorder pharmacotherapy. Here, the role of TLRs in neuroimmunology, treatment, and management of neuropsychiatric disorders is discussed. We recommend longitudinal studies to comparatively assess the cell-type-specific expression of TLRs during treatment, illness progression, and remission. Also, further research should explore molecular insights into TLRs regulation and related pathways.

Differences in Neuropathology between Nitroglycerin-Induced Mouse Models of Episodic and Chronic Migraine

Multiple animal models of migraine have been used to develop new therapies. Understanding the transition from episodic (EM) to chronic migraine (CM) is crucial. We established models mimicking EM and CM pain and assessed neuropathological differences. EM and CM models were induced with single NTG or multiple injections over 9 days. Mechanical hypersensitivity was assessed. Immunofluorescence utilized c-Fos, NeuN, and Iba1. Proinflammatory and anti-inflammatory markers were analyzed. Neuropeptides (CGRP, VIP, PACAP, and substance P) were assessed. Mechanical thresholds were similar. Notable neuropathological distinctions were observed in Sp5C and ACC. ACC showed increased c-Fos and NeuN expression in CM (p < 0.001) and unchanged in EM. Sp5C had higher c-Fos and NeuN expression in EM (p < 0.001). Iba1 was upregulated in Sp5C of EM and ACC of CM (p < 0.001). Proinflammatory markers were strongly expressed in Sp5C of EM and ACC of CM. CGRP expression was elevated in both regions and was higher in CM. VIP exhibited higher levels in the Sp5C of EM and ACC of CM, whereas PACAP and substance P were expressed in the Sp5C in both models. Despite similar thresholds, distinctive neuropathological differences in Sp5C and ACC between EM and CM models suggest a role in the EM to CM transformation.

Breaking the cycle: unraveling the diagnostic, pathophysiological and treatment challenges of refractory migraine

Background

Refractory migraine is a poorly described complication of migraine in which migraine has chronified and become resistant to standard treatments. The true prevalence is unknown, but medication resistance is common in headache clinic patient populations. Given the lack of response to treatment, this patient population is extremely difficult to treat with limited guidance in the literature.

Objective

To review the diagnostic, pathophysiological, and management challenges in the refractory migraine population.

Discussion

There are no accepted, or even ICHD-3 appendix, diagnostic criteria for refractory migraine though several proposed criteria exist. Current proposed criteria often have low bars for refractoriness while also not meeting the needs of pediatrics, lower socioeconomic status, and developing nations. Pathophysiology is unknown but can be hypothesized as a persistent "on" state as a progression from chronic migraine with increasing central sensitization, but there may be heterogeneity in the underlying pathophysiology. No guidelines exist for treatment of refractory migraine; once all guideline-based treatments are tried, treatment consists of n-of-1 treatment trials paired with non-pharmacologic management.

Conclusion

Refractory migraine is poorly described diagnostically, its pathophysiology can only be guessed at by extension of chronic migraine, and treatment is more the art than science of medicine. Navigating care of this refractory population will require multidisciplinary care models and an emphasis on future research to answer these unknowns.

Targeting Nociceptive Neurons and Transient Receptor Potential Channels for the Treatment of Migraine

Migraine is a neurovascular disorder that affects approximately 12% of the global population. While its exact causes are still being studied, researchers believe that nociceptive neurons in the trigeminal ganglia play a key role in the pain signals of migraine. These nociceptive neurons innervate the intracranial meninges and convey pain signals from the meninges to the thalamus. Targeting nociceptive neurons is considered promising due to their accessibility and distinct molecular profile, which includes the expression of several transient receptor potential (TRP) channels. These channels have been linked to various pain conditions, including migraine. This review discusses the role and mechanisms of nociceptive neurons in migraine, the challenges of current anti-migraine drugs, and the evidence for well-studied and emerging TRP channels, particularly TRPC4, as novel targets for migraine prevention and treatment.

Stimulation of CGRP-expressing neurons in the medial cerebellar nucleus induces light and touch sensitivity in mice

Calcitonin gene-related peptide (CGRP) is considered a major player in migraine pathophysiology. However, the location and mechanisms of CGRP actions in migraine are not clearly elucidated. One important question yet to be answered is: Does central CGRP signaling play a role in migraine? One candidate site is the cerebellum, which serves as a sensory and motor integration center and is activated in migraine patients. The cerebellum has the most CGRP binding sites in the central nervous system and a deep cerebellar nucleus, the medial nucleus (MN), expresses CGRP (MN^CGRP). A previous study demonstrated that CGRP delivery into the cerebellum induced migraine-like behaviors. We hypothesized that stimulation of MN^CGRP neurons might induce migraine-like behaviors. To test the hypothesis, we used an optogenetic strategy using Calca^Cre/+ mice to drive Cre-dependent expression of channelrhodopsin-2 selectively in CGRP neurons in the cerebellar MN. A battery of behavioral tests was done to assess preclinical behaviors that are surrogates of migraine symptoms, including light aversion, cutaneous allodynia, and spontaneous pain when MN^CGRP neurons were optically stimulated. Motor functions were also assessed. Optical stimulation of MN^CGRP neurons decreased the time spent in the light, which was coupled to increased time spent resting in the dark, but not the light. These changes were only significant in female mice. Plantar tactile sensitivity was increased in the ipsilateral paws of both sexes, but contralateral paw data were less clear. There was no significant increase in anxiety-like behavior, spontaneous pain (squint), or changes in gait. These discoveries reveal that MN^CGRP neurons may contribute to migraine-like sensory hypersensitivity to light and touch.

CGRP Administration Into the Cerebellum Evokes Light Aversion, Tactile Hypersensitivity, and Nociceptive Squint in Mice

The neuropeptide calcitonin gene-related peptide (CGRP) is a major player in migraine pathophysiology. Previous preclinical studies demonstrated that intracerebroventricular administration of CGRP caused migraine-like behaviors in mice, but the sites of action in the brain remain unidentified. The cerebellum has the most CGRP binding sites in the central nervous system and is increasingly recognized as both a sensory and motor integration center. The objective of this study was to test whether the cerebellum, particularly the medial cerebellar nuclei (MN), might be a site of CGRP action. In this study, CGRP was directly injected into the right MN of C57BL/6J mice via a cannula. A battery of tests was done to assess preclinical behaviors that are surrogates of migraine-like symptoms. CGRP caused light aversion measured as decreased time in the light zone even with dim light. The mice also spent more time resting in the dark zone, but not the light, along with decreased rearing and transitions between zones. These behaviors were similar for both sexes. Moreover, significant responses to CGRP were seen in the open field assay, von Frey test, and automated squint assay, indicating anxiety, tactile hypersensitivity, and spontaneous pain, respectively. Interestingly, CGRP injection caused significant anxiety and spontaneous pain responses only in female mice, and a more robust tactile hypersensitivity in female mice. No detectable effect of CGRP on gait was observed in either sex. These results suggest that CGRP injection in the MN causes light aversion accompanied by increased anxiety, tactile hypersensitivity, and spontaneous pain. A caveat is that we cannot exclude contributions from other cerebellar regions in addition to the MN due to diffusion of the injected peptide. These results reveal the cerebellum as a new site of CGRP actions that may contribute to migraine-like hypersensitivity.

Pain sensitivities predict prophylactic treatment outcomes of flunarizine in chronic migraine patients: A prospective study

BACKGROUND

We aimed to assess the differences in quantitative sensory testing between chronic migraine and healthy controls and to explore the association between pain sensitivities and outcomes in chronic migraine following preventive treatment.

METHODS

In this prospective open-label study, preventive-naïve chronic migraine and healthy controls were recruited, and cold, heat, mechanical punctate, and pressure pain thresholds over the dermatomes of first branch of trigeminal nerve and first thoracic nerve were measured by quantitative sensory testing at baseline. Chronic migraines were treated with flunarizine and treatment response was defined as ≥50% reduction in the number of monthly headache days over the 12-week treatment period.

RESULTS

Eighty-four chronic migraines and fifty age-and-sex-matched healthy controls were included in the analysis. The chronic migraine had higher cold pain thresholds over the dermatomes of the first branch of trigeminal nerve and the first thoracic nerve (p < 0.001 and < 0.001), lower pressure pain thresholds over the dermatomes of the first thoracic nerve (p = 0.003), heat pain thresholds over the dermatomes of the first branch of the trigeminal nerve and the first thoracic nerve (p < 0.001 and p = 0.015) than healthy controls. After treatment, 24/84 chronic migraine had treatment response. The responders with relatively normal pain sensitivity had higher heat pain thresholds over the dermatome of the first branch of the trigeminal nerve (p = 0.002), mechanical punctate pain thresholds over the dermatomes of the first branch of the trigeminal nerve (p = 0.023), and pressure pain thresholds over the dermatomes of the first branch of the trigeminal nerve (p = 0.026) than the hypersensitive non-responders. Decision tree analysis showed that patients with mechanical punctate pain threshold over the dermatomes of the first branch of the trigeminal nerve > 158 g (p = 0.020) or heat pain threshold over the dermatome of the first branch of the trigeminal nerve > 44.9°C (p = 0.002) were more likely to be responders.

CONCLUSIONS

Chronic migraine were generally more sensitive compared to healthy controls. Preventive treatment with flunarizine should be recommended particularly for chronic migraine who have relatively normal sensitivity to mechanical punctate or heat pain.Trial registration: This study was registered on ClinicalTrials.gov (Identifier: NCT02747940).

Alternative Splicing of Neuropeptide Prohormone and Receptor Genes Associated with Pain Sensitivity Was Detected with Zero-Inflated Models

Migraine is often accompanied by exacerbated sensitivity to stimuli and pain associated with alternative splicing of genes in signaling pathways. Complementary analyses of alternative splicing of neuropeptide prohormone and receptor genes involved in cell–cell communication in the trigeminal ganglia and nucleus accumbens regions of mice presenting nitroglycerin-elicited hypersensitivity and control mice were conducted. De novo sequence assembly detected 540 isoforms from 168 neuropeptide prohormone and receptor genes. A zero-inflated negative binomial model that accommodates for potential excess of zero isoform counts enabled the detection of 27, 202, and 12 differentially expressed isoforms associated with hypersensitivity, regions, and the interaction between hypersensitivity and regions, respectively. Skipped exons and alternative 3′ splice sites were the most frequent splicing events detected in the genes studied. Significant differential splicing associated with hypersensitivity was identified in CALCA and VGF neuropeptide prohormone genes and ADCYAP1R1, CRHR2, and IGF1R neuropeptide receptor genes. The prevalent region effect on differential isoform levels (202 isoforms) and alternative splicing (82 events) were consistent with the distinct splicing known to differentiate central nervous structures. Our findings highlight the changes in alternative splicing in neuropeptide prohormone and receptor genes associated with hypersensitivity to pain and the necessity to target isoform profiles for enhanced understanding and treatment of associated disorders such as migraine.

Cutaneous Allodynia in Migraine: A Narrative Review

Objective

In the present work, we conduct a narrative review of the most relevant literature on cutaneous allodynia (CA) in migraine.

Background

CA is regarded as the perception of pain in response to non-noxious skin stimulation. The number of research studies relating to CA and migraine has increased strikingly over the last few decades. Therefore, the clinician treating migraine patients must recognize this common symptom and have up-to-date knowledge of its importance from the pathophysiological, diagnostic, prognostic and therapeutic point of view.

Methods

We performed a comprehensive narrative review to analyze existing literature regarding CA in migraine, with a special focus on epidemiology, pathophysiology, assessment methods, risk for chronification, diagnosis and management. PubMed and the Cochrane databases were used for the literature search.

Results

The prevalence of CA in patients with migraine is approximately 60%. The mechanisms underlying CA in migraine are not completely clarified but include a sensitization phenomenon at different levels of the trigemino-talamo-cortical nociceptive pathway and dysfunction of brainstem and cortical areas that modulate thalamocortical inputs. The gold standard for the assessment of CA is quantitative sensory testing (QST), but the validated Allodynia 12-item questionnaire is preferred in clinical setting. The presence of CA is associated with an increased risk of migraine chronification and has therapeutic implications.

Conclusions

CA is a marker of central sensitization in patients with migraine that has been associated with an increased risk of chronification and may influence therapeutic decisions.

Transient Receptor Potential Channel 4 Small-Molecule Inhibition Alleviates Migraine-Like Behavior in Mice

Migraine is a common neurological disorder with few available treatment options. Recently, we have demonstrated the role of transient receptor potential cation channel subfamily C member 4 (TRPC4) in itch and the modulation of the calcitonin gene-related peptide (CGRP), a biomarker and emerging therapeutic target for migraine. In this study, we characterized the role of TRPC4 in pain and evaluated its inhibition as anti-migraine pain therapy in preclinical mouse models. First, we found that TRPC4 is highly expressed in trigeminal ganglia and its activation not only mediates itch but also pain. Second, we demonstrated that the small-molecule inhibitor ML204, a specific TRPC4 antagonist, significantly reduced episodic and chronic migraine-like behaviors in male and female mice after injection of nitroglycerin (NTG), a well-known migraine inducer in rodents and humans. Third, we found a significant decrease in CGRP protein levels in the plasma of both male and female mice treated with ML-204, which largely prevented the development of chronic migraine-like behavior. Using sensory neuron cultures, we confirmed that activation of TRPC4 elicited release of CGRP, which was significantly diminished by ML-204. Collectively, our findings identify TRPC4 in peripheral sensory neurons as a mediator of CGRP release and NTG-evoked migraine. Since a TRPC4 antagonist is already in clinical trials, we expect that this study will rapidly lead to novel and effective clinical treatments for migraineurs.

Interleukin-6 induces spatially dependent whole-body hypersensitivity in rats: implications for extracephalic hypersensitivity in migraine

Background

Migraine is a complex neurological disorder that is characterized by throbbing head pain, increased sensitivity to light, sound, and touch, as well as nausea and fatigue. It is one of the most common and most disabling disorders globally but mechanisms causing migraine are poorly understood. While head pain is a typical feature of attacks, they also often present with cutaneous hypersensitivity in the rest of the body. In contrast, primary pain conditions in the lower parts of the body are less commonly associated with cephalic hypersensitivity. Previous studies indicate that application of stimuli to the meninges of rodents causes cutaneous facial as well as hindpaw hypersensitivity. In the present study, we asked whether widespread hypersensitivity is a unique feature of dural stimulation or whether body-wide responses occur similarly when the same stimulus is given in other locations.

Methods

Rats were given the same dose of IL-6 either via dural, intraplantar, subcutaneous, intramuscular, intracisternal, or intrathecal injection. Cutaneous facial and hindpaw allodynia was assessed using Von Frey following injection into each location.

Results

Hindpaw allodynia was observed following dural and intraplantar injection of IL-6 in both males and females. Hindpaw allodynia was only observed in females following intracisternal and intrathecal IL-6 injections. In contrast, facial allodynia was only observed in either sex following dural and intracisternal injections, which would activate meningeal afferents and the trigeminal nucleus caudalis (TNC), respectively.

Conclusions

Here we show that while stimulation of upper body regions with IL-6 including the meninges and brainstem can cause widespread hypersensitivity spreading to the paws, similar stimulation of the lower body does not cause the spread of hypersensitivity into the head. These data are consistent with the observations that whole body hypersensitivity is specific to conditions such as migraine where pain is present in the head and they may provide insight into co-morbid pain states associated with migraine.

Is Allodynia a Determinant Factor in the Effectiveness of Transcranial Direct Current Stimulation in the Prophylaxis of Migraine?

OBJECTIVES

Allodynia, the clinical marker of central sensitization, affects even simple daily living activities and increases the tendency for migraine to be more resistant to treatment and have a chronic course. Migraine that impairs quality of life can often be treated with variable pharmaceutical agents, but with various side effects. Transcranial direct current stimulation (tDCS) is a potential alternative treatment for migraine prophylaxis.

MATERIALS AND METHODS

Seventy-seven patients diagnosed with migraine (48 with allodynia and 29 without allodynia) were included in the study. Randomly, 41 of the 77 patients received sham stimulation and 36 patients underwent three sessions of anodal left primary motor cortex stimulation for 2 mA, 20 min. Migraine attack characteristics (frequency, severity, and duration) and analgesic drug use were followed with headache diaries for one month after the stimulation.

RESULTS

After tDCS, migraine attack frequency (p = 0.021), the number of headache days (p = 0.005), duration of attacks (p = 0.008), and symptomatic analgesic drug use (p = 0.007) decreased in patients receiving active tDCS, compared to the sham group. The therapeutic gain of tDCS was calculated as 44% (95% confidence interval [CI]: 22-60%) for headache days and 76% (95% CI: 55-86) for headache duration. Response to tDCS treatment was higher in patients without allodynia (60% vs. 24%; p = 0.028) and allodynia came out as an independent predictor of response to tDCS with logistic regression analysis. Side effects were rare and similar to the sham group.

CONCLUSIONS

tDCS is a safe, efficacious, and fast method for migraine prophylaxis. However, the administration of tDCS before allodynia occurs, that is, before central sensitization develops, will provide increased responsiveness to the treatment.

SIGNIFICANCE

tDCS is more effective before the development of allodynia, but it also improves the quality of life even after the development of allodynia.

Effectiveness of paranasal air suction on acute migraine using portable air sucker - a randomized, double blind study

BACKGROUND

Migraine is a primary headache disorder and is the most common disabling primary headache disorder that occurs in children and adolescents. A recent study showed that paranasal air suction can provide relief to migraine headache. However, in order to get the maximum benefit out of it, an easy to use effective air sucker should be available. Aiming to fulfil the above requirement, a randomized, double blind control clinical trial was conducted to investigate the efficacy of a recently developed low-pressure portable air sucker.

METHODS

Eighty-six Sri Lankan school children of age 16-19 years with migraine were enrolled for the study. They were randomly allocated into two groups, and one group was subjected to six intermittent ten-second paranasal air suctions using the portable air sucker for 120 s. The other group was subjected to placebo air suction (no paranasal air suction). The effect of suction using portable air sucker was the primary objective but side of headache, type of headache, and gender were also studied as source variables. The primary response studied was severity of headache. In addition, left and right supraorbital tenderness, photophobia, phonophobia, numbness over the face and scalp, nausea and generalized tiredness/weakness of the body were studied. The measurements on all those variables were made before and after suction, and the statistical analysis was performed based on before and after differences. As a follow-up, patients were monitored for 24-h period.

RESULTS

There was a significant reduction in the severity of headache pain (OR = 25.98, P < 0.0001), which was the primary outcome variable, and other migraine symptoms studied, tenderness (left) (OR = 289.69, P < 0.0001), tenderness (right) (OR > 267.17, P < 0.0001), photophobia (OR = 2115.6, P < 0.0001), phonophobia (OR > 12.62, P < 0.0001) nausea (OR > 515.59, P < 0.0001) and weakness (OR = 549.06, P < 0.0001) except for numbness (OR = 0.747, P = 0.67) in the treatment group compared to the control group 2 min after the suction. These symptoms did not recur within 24-h period and there were no significant side effects recorded during the 24-h observation period.

CONCLUSION

This pilot study showed that low-pressure portable air sucker is effective in paranasal air suction, and suction for 120 s using the sucker can provide an immediate relief which can last for more than 24-h period without any side effects.

TRAIL REGISTRATION

Clinical Trial Government Identification Number - 1548/2016. Ethical Clearance Granted Institute - Medical Research Institute, Colombo, Sri Lanka (No 38/2016). Sri Lanka Clinical Trial Registration No: SLCTR/2017/018 . Date of registration = 29/ 06/2017. Approval Granting Organization to use the device in the clinical trial- National Medicines Regulatory Authority Sri Lanka (16 Jan 2018), The device won award at Geneva international inventers exhibition in 2016 and President award in 2018 in Sri Lanka. It is a patented device in Sri Lanka and patent number was SLKP/1/18295. All methods were carried out in accordance with CONSORT 2010 guidelines.

An underrepresented majority: A systematic review utilizing allodynic criteria to examine the present scarcity of discrete animal models for episodic migraine

BACKGROUND

Despite increasing evidence differentiating episodic and chronic migraine, little work has determined how currently utilized animal models of migraine best represent each distinct disease state.

AIM

In this review, we seek to characterize accepted preclinical models of migraine-like headache by their ability to recapitulate the clinical allodynic features of either episodic or chronic migraine.

METHODS

From a search of the Pu bMed database for "animal models of migraine", "headache models" and "preclinical migraine", we identified approximately 80 recent (within the past 20 years) publications that utilized one of 10 different models for migraine research. Models reviewed fit into one of the following categories: Dural KCl application, direct electrical stimulation, nitroglycerin administration, inflammatory soup injection, CGRP injection, medication overuse, monogenic animals, post-traumatic headache, specific channel activation, and hormone manipulation. Recapitulation of clinical features including cephalic and extracephalic hypersensitivity were evaluated for each and compared.

DISCUSSION

Episodic migraineurs comprise over half of the migraine population, yet the vast majority of current animal models of migraine appear to best represent chronic migraine states. While some of these models can be modified to reflect episodic migraine, there remains a need for non-invasive, validated models of episodic migraine to enhance the clinical translation of migraine research.

DAGLα Inhibition as a Non-invasive and Translational Model of Episodic Headache

Recent findings suggested that Clinical Endocannabinoid Deficiency underlies the pathophysiology of pain disorders, including migraine and headache. In models of medication overuse headache induced by sustained administration of sumatriptan or morphine, 2-AG levels were selectively depleted in the periaqueductal gray (PAG) and anandamide (AEA) increased in the cortex suggesting distinct regulation of the endocannabinoid system during headache pain. These results led to the hypothesis that blockade of DAGL, to reduce 2-AG levels would induce headache-like behaviors as a new, translationally relevant model of episodic headache. Our study investigated whether non-selective and selective blockade of DAGL, the main biosynthetic enzyme for 2-AG, induced periorbital and hind-paw allodynia, photophobia, anxiety-like behaviors, responsivity to abortive anti-migraine agents, and 2-AG/AEA levels. Injection of non-selective DAGL (DH376, 10 mg/kg, IP) and selective DAGLα (LEI106, 20 mg/kg, IP) inhibitors, but not DAGLβ agents, induced facial sensitivity in 100% and ∼60% of female and male rats, respectively, without induction of peripheral sensitivity. Notably, male rats showed significantly less sensitivity than female rats after DAGLα inhibition, suggesting sexual dimorphism in this mechanism. Importantly, LEI106 induced periorbital allodynia was attenuated by administration of the clinically available abortive antimigraine agents, sumatriptan and olcegepant. Selective DAGLα inhibition induced significant photophobia as measured by the light-dark box, without anxiety like behaviors or changes in voluntary movement. Analysis of AEA and 2-AG levels at the time of peak pain sensitivity revealed reductions in 2-AG in the visual cortex and periaqueductal gray (PAG), without altering anandamide or significantly increasing diacylglycerol levels. These results provide foundational evidence for DAGL-2AG in the induction of headache-like pain and photophobia without extracephalic allodynia, thus modeling the clinical episodic migraine. Mechanistically, behavioral measures of headache sensitivity after DAGL inhibition suggests that reduced 2-AG signaling in the cortex and PAG, but not the trigeminal nucleus caudalis or trigeminal ganglia, drives headache initiation. Therefore, episodic DAGL inhibition, which reduces the time, cost, and invasiveness of currently accepted models of headache, may fill the need for episodic migraine/headache models mirroring clinical presentation. Moreover, use of this approach may provide an avenue to study the transition from episodic to chronic headache.

Treatment effects on pain catastrophizing and cutaneous allodynia symptoms in women with migraine and overweight/obesity

OBJECTIVE

Pain catastrophizing and cutaneous allodynia represent two risk factors for greater headache-related disability. Yet, there is limited knowledge of the extent to which these risk factors are modifiable and whether nonpharmacological treatment-related changes are associated with migraine improvements. Using data from the Women's Health and Migraine (WHAM) study, a randomized controlled trial that compared effects of behavioral weight loss (BWL) and migraine education (ME) in women with migraine and overweight/obesity, we tested whether: (a) BWL versus ME produced greater changes in pain catastrophizing and allodynia from baseline across posttreatment and follow-up time points, and (b) whether these improvements were associated with improvements in headache disability.

METHOD

Women (N = 110) were randomly assigned to 16 weeks of either BWL or ME and assessed at baseline, posttreatment, and follow up (32 weeks). Multilevel mixed effects modeling tested: (a) for between-groups differences in pain catastrophizing and allodynia changes over time, and (b) associations of changes in pain catastrophizing and allodynia with changes in headache disability, adjusting for migraine severity and weight loss.

RESULTS

Both BWL and ME had significant reductions in pain catastrophizing and allodynia from baseline to posttreatment and follow up, and the improvements were comparable across conditions. Reductions in pain catastrophizing and cutaneous allodynia were associated with significant reductions in headache disability, even when controlling for intervention-related improvements in migraine and weight loss.

CONCLUSION

Pain catastrophizing and allodynia are not only reduced after nonpharmacologic treatments for migraine, but greater improvements are associated with greater reductions in headache-related disability, independent of migraine severity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Ubrogepant does not induce latent sensitization in a preclinical model of medication overuse headache

BACKGROUND

Ubrogepant, a small-molecule calcitonin gene-related peptide receptor antagonist, was recently approved as an oral medication for the acute treatment of migraine. This study aimed to determine whether ubrogepant shows efficacy in a preclinical model of migraine-like pain and whether repeated oral administration of ubrogepant induces latent sensitization relevant to medication overuse headache in rats.

METHODS

A "two-hit" priming model of medication overuse headache was used. Female Sprague-Dawley rats received six oral doses of sumatriptan 10 mg/kg over 2 weeks to induce latent sensitization (i.e. "priming"). Cutaneous allodynia was measured periodically over 20 days in the periorbital and hindpaw regions using von Frey filaments. The rats were then subjected to a 1-hour bright light stress challenge on two consecutive days. At the start of the second bright light stress exposure, oral sumatriptan 10 mg/kg, oral ubrogepant 25, 50, or 100 mg/kg, or vehicle was administered; thereafter, cephalic and hindpaw sensory thresholds were monitored hourly over 5 hours to determine the efficacy of ubrogepant in reversing bright light stress-induced cutaneous allodynia. A dose of ubrogepant effective in the medication overuse headache model (100 mg/kg) was then selected to determine if repeated administration would produce latent sensitization. Rats were administered six oral doses of ubrogepant 100 mg/kg, sumatriptan 10 mg/kg (positive control), or vehicle over 2 weeks, and cutaneous allodynia was evaluated regularly. Testing continued until mechanosensitivity returned to baseline levels. Rats were then challenged with bright light stress on days 20 and 21, and periorbital and hindpaw cutaneous allodynia was measured. On days 28 to 32, the same groups received a nitric oxide donor (sodium nitroprusside 3 mg/kg, i.p.), and cutaneous allodynia was assessed hourly over 5 hours.

RESULTS

Sumatriptan elicited cutaneous allodynia in both cephalic and hindpaw regions; cutaneous allodynia resolved to baseline levels after cessation of drug administration (14 days). Sumatriptan priming resulted in generalized and delayed cutaneous allodynia, evoked by either bright light stress (day 21) or nitric oxide donor (day 28). Ubrogepant dose-dependently blocked both stress- and nitric oxide donor-induced cephalic and hindpaw allodynia in the sumatriptan-induced medication overuse headache model with a 50% effective dose of ∼50 mg/kg. Unlike sumatriptan, ubrogepant 100 mg/kg in repeated effective doses did not produce cutaneous allodynia or latent sensitization.

CONCLUSIONS

Both ubrogepant and sumatriptan demonstrated efficacy as acute medications for stress- and nitric oxide donor-evoked cephalic allodynia in a preclinical model of medication overuse headache, consistent with their clinical efficacy in the acute treatment of migraine. However, in contrast to sumatriptan, repeated treatment with ubrogepant did not induce cutaneous allodynia or latent sensitization. These studies suggest ubrogepant may offer an effective acute treatment of migraine without risk of medication overuse headache.Trial Registration Number: Not applicable.

Evaluation of LY573144 (lasmiditan) in a preclinical model of medication overuse headache

BACKGROUND

Medication overuse is a significant issue that complicates the treatment of headache disorders. The most effective medications for the acute treatment of migraine all have the capacity to induce medication overuse headache (MOH). Novel acute migraine-specific treatments are being developed. However, because the mechanism(s) underlying medication overuse headache are not well understood, it is difficult to predict whether any particular acute medication will induce MOH in susceptible individuals. LY573144 (lasmiditan), a 5-HT_1F receptor agonist, has recently been shown to be effective in the acute treatment of migraine in phase 3 trials. The aim of this study is to determine whether frequent administration of lasmiditan induces behaviors consistent with MOH in a pre-clinical rat model.

METHODS

Sprague Dawley rats were administered six doses of lasmiditan (10 mg/kg), sumatriptan (10 mg/kg), or sterile water orally over 2 weeks and cutaneous allodynia was evaluated regularly in the periorbital and hindpaw regions using von Frey filaments. Testing continued until mechanosensitivity returned to baseline levels. Rats were then submitted to bright light stress (BLS) or nitric oxide (NO) donor administration and were again evaluated for cutaneous allodynia in the periorbital and hindpaw regions hourly for 5 hours.

RESULTS

Both lasmiditan and sumatriptan exhibited comparable levels of drug-induced cutaneous allodynia in both the periorbital and hindpaw regions, which resolved after cessation of drug administration. Both lasmiditan and sumatriptan pre-treatment resulted in cutaneous allodynia that was evoked by either BLS or NO donor.

CONCLUSIONS

In a pre-clinical rat model of MOH, oral lasmiditan, like sumatriptan, induced acute transient cutaneous allodynia in the periorbital and hindpaw regions that after resolution could be re-evoked by putative migraine triggers. These results suggest that lasmiditan has the capacity to induce MOH through persistent latent peripheral and central sensitization mechanisms.

Signaling Interaction between Facial and Meningeal Inputs of the Trigeminal System Mediates Peripheral Neurostimulation Analgesia in a Rat Model of Migraine

Peripheral neurostimulation within the trigeminal nerve territory has been used for pain alleviation during migraine attacks, but the mechanistic basis of this non-invasive intervention is still poorly understood. In this study, we investigated the therapeutic role of peripheral stimulation of the trigeminal nerve, which provides homosegmental innervation to intracranial structures, by assessing analgesic effects in a nitroglycerin (NTG)-induced rat model of migraine. As a result of neurogenic inflammatory responses in the trigeminal nervous system, plasma protein extravasation was induced in facial skin by applying noxious stimulation to the dura mater. Noxious chemical stimulation of the dura mater led to protein extravasation in facial cutaneous tissues and caused mechanical sensitivity. Trigeminal ganglion (TG) neurons were double-labeled via retrograde tracing to detect bifurcated axons. Extracellular recordings of wide dynamic range (WDR) neurons in the spinal trigeminal nucleus caudalis (Sp5C) demonstrated the convergence and interaction of inputs from facial tissues and the dura mater. Peripheral neurostimulation of homotopic facial tissues represented segmental pain inhibition on cephalic cutaneous allodynia in the migraine model. The results indicated that facial territories and intracranial structures were directly connected with each other through bifurcated double-labeled neurons in the TG and through second-order WDR neurons. Homotopic stimulation at the C-fiber intensity threshold resulted in much stronger inhibition of analgesia than the same intensity of heterotopic stimulation. These results provide novel evidence for the neurological bases through which peripheral neurostimulation may be effective in treating migraine in clinical practice.

Impact of Therapeutic Interventions on Pain Intensity and Endogenous Pain Modulation in Knee Osteoarthritis: A Systematic Review and Meta-analysis

OBJECTIVE

To study the impact of therapeutic interventions on pain analgesia and endogenous pain modulation in knee osteoarthritis (KOA).

DESIGN

Systematic review and meta-analysis.

METHODS

We searched for KOA randomized clinical trials and observational studies with data on therapeutic interventions comparing pain intensity, temporal summation (TS), and conditioned pain modulation (CPM) scores relative to control. These data were pooled as Hedge's g. To study the relationship between pain intensity and TS/CPM, we performed metaregression with 10,000 Monte-Carlo permutations.

RESULTS

We reviewed 11 studies (559 participants). On studying all the interventions together, we found no significant changes in pain modulation, TS, or CPM. Our findings show that this lack of difference is likely because surgical and nonsurgical interventions resulted in contrary effects. Metaregression significantly correlated pain reduction with normalization of TS and CPM.

CONCLUSIONS

We demonstrate an association between pain reduction and TS/CPM normalization. Though we cannot directly compare these interventions, the results allow us to draw hypotheses on potential practice schemas. Recovering defective endogenous pain modulation mechanisms may help establish long-term analgesia. However, to validate these paradigms as robust clinical biomarkers, further investigation into their mechanisms would be necessary. The registration number for this review is CRD42017072066.

Calcitonin gene-related peptide (CGRP): role in migraine pathophysiology and therapeutic targeting

Introduction: The neuropeptide calcitonin gene-related peptide (CGRP) is recognized as a critical player in migraine pathophysiology. Excitement has grown regarding CGRP because of the development and clinical testing of drugs targeting CGRP or its receptor. While these drugs alleviate migraine symptoms in half of the patients, the remaining unresponsive half of this population creates an impetus to address unanswered questions that exist in this field.Areas covered: We describe the role of CGRP in migraine pathophysiology and CGRP-targeted therapeutics currently under development and in use. We also discuss how a second CGRP receptor may provide a new therapeutic target.Expert opinion: CGRP-targeting drugs have shown a remarkable safety profile. We speculate that this may reflect the redundancy of peptides within the CGRP family and a second CGRP receptor that may compensate for reduced CGRP activity. Furthermore, we propose that an inherent safety feature of peptide-blocking antibodies is attributed to the fundamental nature of peptide release, which occurs as a large bolus in short bursts of volume transmission. These facts support the development of more refined CGRP therapeutic drugs, as well as drugs that target other neuropeptides. We believe that the future of migraine research is bright with exciting advances on the horizon.

Studies on the Mechanism of Glutamate Metabolism in NTG-Induced Migraine Rats Treated with DCXF

Objective

To explore the mechanism of the antimigraine effect by active components extracted from the Dachuanxiong prescription (DCXF), nitroglycerin- (NTG-) induced migraine rats were used to detect the change of glutamate metabolism and the overall metabolic profile at different time points in the serum and Trigeminocervical complex(TCC) samples.

Method

The biological samples that were obtained at 30 minutes, 60 minutes, and 90 minutes after model establishment or drug administration were tested by GC-TOF-MS. Then, real-time PCR and western blot were applied to detect changes in the expression of some substances involved in glutamate metabolism.

Result

DCXF could improve the metabolic profile of serum and TCC in migraine rats and showed the time trend of treatment, mainly involved by amino acid metabolism (glutamate, aspartic acid, and alanine metabolism). In addition, DCXF could increase the expressions of GS at 60 min and 90 min and EAAT1 at 90 min. The results of GS protein were similar to that of mRNA.

Conclusion

The antimigraine effect of DCXF could be achieved by improving the metabolic profile and increasing the expressions of GS and EAAT1 to promote the glutamate cycle of TCC and serum samples in NTG-induced migraine rats to a certain extent.

TRPM8 genetic variant is associated with chronic migraine and allodynia

Background

Many single nucleotide polymorphisms (SNPs) have been reported to be associated with migraine susceptibility. However, evidences for their associations with migraine endophenotypes or subtypes are scarce. We aimed to investigate the associations of pre-identified migraine susceptibility loci in Taiwanese with migraine endophenotypes or subtypes, including chronic migraine and allodynia.

Methods

The associations of six SNPs identified from our previous study, including TRPM8 rs10166942, LRP1 rs1172113, DLG2 rs655484, GFRA1 rs3781545, UPP2 rs7565931, and GPR39 rs10803531, and migraine endophenotypes, including chronic migraine and allodynia were tested. Significant associations in the discovery cohort were validated in the replication cohort. The adjusted odds ratios (aOR) were calculated after controlling for confounders.

Results

In total, 1904 patients (mean age 37.5 ± 12.2 years old, female ratio: 77.7%) including 1077 in the discovery cohort and 827 in the replication cohort were recruited. Of them, 584 (30.7%) had chronic migraine. Of the 6 investigated SNPs, TRPM8 rs10166942 T allele-carrying patients were more likely to have chronic migraine than non-T allele carriers in both discovery and replication cohorts and combined samples (33.7% vs. 25.8%, p = 0.004, aOR = 1.62). In addition, T allele carriers reported more allodynic symptoms than non-T allele carriers (3.5 ± 3.7 vs. 2.6 ± 2.8, p < 0.001). However, allodynia severity did not differ between episodic and chronic migraine patients. No further correlations between genetic variants and endophenotypes were noted for the other SNPs.

Conclusions

TRPM8 may contribute to the pathogenesis of chronic migraine. However, our study did not support allodynia as a link between them. The underlying mechanisms deserve further investigations.

CGRP in Animal Models of Migraine

With the approval of calcitonin gene-related peptide (CGRP) and CGRP receptor monoclonal antibodies by the Federal Drug Administration, a new era in the treatment of migraine patients is beginning. However, there are still many unknowns in terms of CGRP mechanisms of action that need to be elucidated to allow new advances in migraine therapies. CGRP has been studied both clinically and preclinically since its discovery. Here we review some of the preclinical data regarding CGRP in animal models of migraine.

Atypical functional connectivity between the anterior cingulate cortex and other brain regions in a rat model of recurrent headache

We explored the atypical functional connectivity between the anterior cingulate cortex and other brain areas in rats subjected to repeated meningeal nociception. The rat model was established by infusing an inflammatory soup through supradural catheters in conscious rats. Rats were subdivided according to the frequency of the inflammatory soup infusions. Functional connectivity analysis seeded on the anterior cingulate cortex was performed on rats 21 days after inflammatory soup infusion. Glyceryl trinitrate was injected following baseline scanning in the low-frequency inflammatory soup group and magnetic resonance imaging data were acquired 1 h after the injection. The rats exhibited nociceptive behavior after high-frequency inflammatory soup infusion. The anterior cingulate cortex showed increased functional connectivity with the cerebellum in the inflammatory soup groups. The medulla showed increased functional connectivity with the anterior cingulate cortex in the ictal period in the low-frequency inflammatory soup rats. Several areas showed increased functional connectivity with the anterior cingulate cortex in the high-frequency inflammatory soup group, including the pontine tegmentum, midbrain, thalamus, corpus callosum, hippocampus, and retrosplenial, visual, sensory, and motor cortices. This study indicated that the medulla participates in the early stage of a migraine attack and may be associated with the initiation of migraine. Sensitization of the trigeminal nociceptive pathway might contribute to the cutaneous allodynia seen in chronic migraine. Brain areas important for memory function may be related to the chronification of migraine. Electrophysiological studies should examine those migraine-related areas and provide new targets for migraine treatment and prevention.

Associated Factors and Clinical Implication of Cutaneous Allodynia in Patients with Cluster Headache: A Prospective Multicentre Study

Cutaneous allodynia (CA) is an abnormal pain in response to non-painful stimuli. In the present study, we sought to investigate the presence of CA, its associated factors, and its clinical implications in patients with cluster headache (CH). In this cross-sectional study, we analysed data from a prospective multicentre registry enrolling consecutive patients with CH. We identified CA during and between headache attacks using the 12-item Allodynia Symptom Checklist (ASC) administered during the CH bout period. Comorbid depression and anxiety were ascertained using the Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder (GAD-7) scales. Headache impact was evaluated using the Headache Impact Test-6 (HIT-6). Of 119 eligible patients, 48 and two (40.3% and 1.7%) had CA during and between headache attacks, respectively. In univariable analyses, total CH duration, major depressive disorder (MDD), and generalized anxiety disorder (GAD) were associated with CA during headache attack. They remained significantly associated with CA during headache attack in multivariable analyses. Patients with CA during headache attack had higher headache impact (P = 0.002). A “50% responder” analysis showed no difference in outcome of acute and preventive treatment between patients with and without CA during headache attack. Patients with CH commonly experienced CA during headache attack, but not between headache attacks. CA during headache attack was associated with disease duration, depression, and anxiety.

Predictors of allodynia in persons with migraine: Results from the Migraine in America Symptoms and Treatment (MAST) study

Background

Cutaneous allodynia is a common clinical feature of migraine that has been associated with reduced efficacy of acute migraine treatments and an increased risk of disease progression.

Objective

Identify factors associated with allodynia in a sample of adults with migraine.

Methods

An online survey panel was used to identify adults with migraine who averaged at least 1 monthly headache day over the previous 3 months. Data on sociodemographics, headache frequency, headache pain intensity, migraine symptom severity, medication use, depression and anxiety, and cutaneous allodynia (via the Allodynia Symptom Checklist) were obtained. Binary logistic modeling predicted the presence of allodynia. Odds ratios and 95% confidence intervals (CI) were calculated.

Results

In total, 15,133 individuals with migraine met the eligibility criteria. Mean age was 43.1 years, 73.0% were female, and 81.0% were Caucasian. Allodynia was present in 39.9%. The fully adjusted model, controlling for sociodemographics and headache features, demonstrated that allodynia was significantly associated with a higher migraine symptom severity score (odds ratio 1.17, confidence interval 1.15, 1.19) and more severe pain intensity (odds ratio 1.11, confidence interval 1.08, 1.14); probable depression and/or anxiety (odds ratio 1.83, confidence interval 1.67, 2.00); and overuse of acute medication (odds ratio 1.23, confidence interval 1.09, 1.38). A higher number of monthly headache days increased the likelihood of allodynia, but the effect was attenuated in the fully adjusted model.

Conclusion

In a representative sample of US adults with migraine, there were significant associations between allodynia and headache frequency and intensity, anxiety and/or depression, symptom severity, and acute medication overuse.

Acute treatment of migraine with external trigeminal nerve stimulation: A pilot trial

Objective:

The main objective of this study was to obtain efficacy data for external trigeminal nerve stimulation (e-TNS) in the acute treatment of migraine in patients using the device at home.

Methods:

This was a single-center, open-label trial conducted at the Rochester Clinical Research Center (Rochester, NY, USA). Patients who met International Classification of Headache Disorders, Third Edition, criteria for migraine with and without aura for ≥1 year and having between 2 and 8 moderate or severe attacks per month were recruited. Patients were advised to treat one migraine attack of moderate to severe intensity that started less than 4 h earlier and was not treated with an acute migraine medication, with a 2-h e-TNS session. Primary outcome measures were pain freedom at 2 h and most bothersome migraine-associated symptom (MBS) freedom at 2 h. Secondary outcome measures were pain relief at 2 h, the absence of migraine-associated symptoms at 2 h, the use of rescue medication between 2 and 24 h, and sustained pain freedom at 24 h.

Results:

Fifty-nine subjects were included in the study, and among them, 48 subjects were eligible for the modified intention-to-treat analysis. After 2 h of e-TNS, 35.4% of the subjects were pain-free, 60.4% were MBS-free, 70.8% had pain relief, and 45.8% were free from all migraine-associated symptoms. Half of the subjects took rescue medication between 2 h and 24 h, and sustained pain freedom at 24 h was achieved for 25.0% of the subjects. Regarding safety, 15 patients reported adverse events, all minor and fully reversible, mainly forehead paresthesia.

Conclusions:

This study shows that e-TNS with the Cefaly® Acute Device is effective, well-tolerated, and safe for the acute treatment of migraine in patients using the device at home. A large, multicenter, randomized, sham-controlled trial is needed to confirm this finding.

Acute migraine therapy with external trigeminal neurostimulation (ACME): A randomized controlled trial

OBJECTIVE

To assess the safety and efficacy of external trigeminal nerve stimulation for acute pain relief during migraine attacks with or without aura via a sham-controlled trial.

METHODS

This was a double-blind, randomized, sham-controlled study conducted across three headache centers in the United States. Adult patients who were experiencing an acute migraine attack with or without aura were recruited on site and randomly assigned 1:1 to receive either verum or sham external trigeminal nerve stimulation treatment (CEFALY Technology) for 1 hour. Pain intensity was scored using a visual analogue scale (0 = no pain to 10 = maximum pain). The primary outcome measure was the mean change in pain intensity at 1 hour compared to baseline.

RESULTS

A total of 109 participants were screened between February 1, 2016 and March 31, 2017. Of these, 106 patients were randomized and included in the intention-to-treat analysis (verum: n = 52; sham: n = 54). The primary outcome measure was significantly more reduced in the verum group than in the sham group: -3.46 ± 2.32 versus -1.78 ± 1.89 ( p < 0.0001), or -59% versus -30% ( p < 0.0001). With regards to migraine subgroups, there was a significant difference in pain reduction between verum and sham for 'migraine without aura' attacks: mean visual analogue scale reduction at 1 hour was -3.3 ± 2.4 for the verum group versus -1.7 ± 1.9 for the sham group ( p = 0.0006). For 'migraine with aura' attacks, pain reduction was numerically greater for verum versus sham, but did not reach significance: mean visual analogue scale reduction at 1 hour was -4.3 ± 1.8 for the verum group versus -2.6 ± 1.9 for the sham group ( p = 0.060). No serious adverse events were reported and five minor adverse events occurred in the verum group.

CONCLUSION

One-hour treatment with external trigeminal nerve stimulation resulted in significant headache pain relief compared to sham stimulation and was well tolerated, suggesting it may be a safe and effective acute treatment for migraine attacks.

STUDY PROTOCOL

ClinicalTrials.gov Identifier: NCT02590939.

Migraine in America Symptoms and Treatment (MAST) Study: Baseline Study Methods, Treatment Patterns, and Gender Differences

OBJECTIVES

To summarize the baseline methods for the Migraine in America Symptoms and Treatment (MAST) Study and evaluate gender differences in sociodemographics and headache features; consultation and diagnosis patterns; and patterns of acute and preventive treatment use for migraine among study participants.

BACKGROUND

The MAST Study is a longitudinal, internet-based panel study of symptoms, approaches to management, and unmet treatment needs among US adults with migraine. This analysis focuses on the initial cross-sectional survey, conducted beginning in 2016, and is intended to update results from earlier national epidemiologic surveys of people with migraine in the United States.

METHODS

Respondents to the MAST Study were recruited from a US nationwide online research panel. Stratified random sampling identified a representative cohort of adults (aged ≥18 years). We administered a validated diagnostic screener based on modified ICHD-3 beta criteria to identify individuals with migraine averaging at least 1 monthly headache day (MHD) over the previous 3 months. A baseline assessment evaluated sociodemographic and headache features, patterns of consultation and diagnosis, and use of acute and preventive medications for migraine. Frequency data and chi-square contrasts (P < .05) were used to compare respondents based on gender.

RESULTS

Baseline survey data (N = 95,821) identified 18,353 respondents who met criteria for migraine, including 15,133 (women n = 11,049, men n = 4084) reporting at least 1 MHD for the preceding 3 months. The mean age of the sample was 43.1 (13.6) years; 73.0% of respondents were women, and 81.0% were Caucasian. Compared with men, women were younger (46.1 vs 42.0 years; P < .001); had more MHDs (5.6 vs 5.3; P < .001); and were more likely to report moderate or severe headache-related disability (45.9% vs 35.8%; P < .001) and cutaneous allodynia (43.7% vs 29.5%; P < .001). The lifetime rate of medical consultation for headache was 79.8% overall and slightly higher in women than in men. Women were more likely than men to have been diagnosed with migraine (48.3% vs 38.8%, P < .001). While 95.1% of people with migraine currently used acute treatment, the majority (58.9%) used over-the-counter (OTC) drugs to the exclusion of prescription drugs, while 11.3% used exclusively prescription drugs, and 20.5% used both. Among acute prescription medication users, women were more likely than men to take triptans (17.7% vs 14.3%, P < .001), while men were more likely than women to take opioids (14.5% vs 9.2%, P < .001). Oral formulations were used predominately (92.7% of the medication users), but men were more likely to use nasal sprays (13.6% vs 9.4%, P < .001) and injectables (7.9% vs 3.4%, P <  .001). Men (14.5%) were also significantly more likely than women (10.4%) to be taking daily oral preventive medication (P < .001).

CONCLUSIONS

The MAST Study identified a large sample of women and men with migraine from a sampling frame that broadly resembles the US population. Low participation rate increases the risk of response bias, however, comparisons with Census data and prior population studies for the demographic and headache characteristics of the current sample suggest that findings are generalizable to the population of people with migraine. Women had more MHDs than men, and they were more likely to report migraine-related disability and cutaneous allodynia. The lifetime consultation rate for headache was relatively high, but many with migraine symptoms reported never having received a diagnosis of migraine from a healthcare professional. Acute prescription and preventive migraine treatments are underused. Migraine persists as an underdiagnosed and undertreated public health problem in 2018, and there are many opportunities to improve the diagnosis and treatment of people with this painful, disabling condition.

Factors associated with acute medication overuse in people with migraine: results from the 2017 migraine in America symptoms and treatment (MAST) study

Background

The MAST Study is a longitudinal, cross-sectional survey study of US adults with migraine. These analyses were conducted to estimate rates of acute medication overuse (AMO) and determine associations of AMO with individual and headache characteristics.

Methods

Eligible respondents had ICHD-3-beta migraine, reported ≥3 monthly headache days (MHDs) in the past 3 months, ≥1 MHD in the past 30 days, and currently took acute headache medication. AMO was defined according to ICHD-3-beta thresholds for monthly days of medication taking when diagnosing medication overuse headache.

Results

Eligible respondents (N = 13,649) had a mean age of 43.4 ± 13.6 years; most were female (72.9%) and Caucasian (81.9%). Altogether, 15.4% of respondents met criteria for AMO. Compared with those not overusing medications, respondents with AMO were significantly more likely to be taking triptans (31.3% vs 14.2%), opioids (23.8% vs 8.0%), barbiturates (7.8% vs 2.7%), and ergot alkaloids (3.1% vs 0.6%) and significantly less likely to be taking NSAIDs (63.3% vs 69.8%) (p < 0.001 for all comparisons). Respondents with AMO had significantly more MHDs (12.9 ± 8.6 vs 4.3 ± 4.3, p  <  0.001); higher migraine symptom severity (17.8 ± 2.7 vs 16.4 ± 3.0, p  <  0.001), higher pain intensity scores (7.4 vs 6.5, p  <  0.001); and higher rates of cutaneous allodynia (53.7% vs 37.5%, p  <  0.001). Adjusted for MHDs, the odds of AMO were increased by each additional year of age (OR 1.02, 95% CI 1.02, 1.03); being married (OR 1.19, 95% CI 1.06, 1.34); smoking (OR 1.54, 95% CI 1.31, 1.81); having psychological symptoms (OR 1.62, 95% CI 1.43, 1.83) or cutaneous allodynia (OR 1.22, 95% CI 1.08, 1.37); and greater migraine symptom severity (OR 1.06, 95% CI 1.04, 1.09) and pain intensity (OR 1.27, 95% CI 1.22, 1.32). Cutaneous allodynia increased the risk of AMO by 61% in males (OR 1.61, 95% CI 1.28, 2.03) but did not increase risk in females (OR 1.08, 95% CI 0.94, 1.25).

Conclusions

AMO was present in 15% of respondents with migraine. AMO was associated with higher symptom severity scores, pain intensity, and rates of cutaneous allodynia. AMO was more likely in triptan, opioid, and barbiturate users but less likely in NSAID users. Cutaneous allodynia was associated with AMO in men but not women. This gender difference merits additional exploration.

Non-headache symptoms in migraine patients

Migraine is one of the most common neurological disorders. In addition to severe headaches, non-headache symptoms associated with migraine attacks as well as co-morbid disorders frequently aggravate the disabling of migraine patients. Some of these symptoms are related to poor outcomes. In this review, we update the advances of studies on certain non-headache symptoms, including visual disturbance, gastrointestinal symptoms, allodynia, vestibular symptoms, and symptoms of co-morbid restless legs syndrome and psychiatric disorders.

Volumetric abnormalities of the brain in a rat model of recurrent headache

Voxel-based morphometry is used to detect structural brain changes in patients with migraine. However, the relevance of migraine and structural changes is not clear. This study investigated structural brain abnormalities based on voxel-based morphometry using a rat model of recurrent headache. The rat model was established by infusing an inflammatory soup through supradural catheters in conscious male rats. Rats were subgrouped according to the frequency and duration of the inflammatory soup infusion. Tactile sensory testing was conducted prior to infusion of the inflammatory soup or saline. The periorbital tactile thresholds in the high-frequency inflammatory soup stimulation group declined persistently from day 5. Increased white matter volume was observed in the rats three weeks after inflammatory soup stimulation, brainstem in the in the low-frequency inflammatory soup-infusion group and cortex in the high-frequency inflammatory soup-infusion group. After six weeks’ stimulation, rats showed gray matter volume changes. The brain structural abnormalities recovered after the stimulation was stopped in the low-frequency inflammatory soup-infused rats and persisted even after the high-frequency inflammatory soup stimulus stopped. The changes of voxel-based morphometry in migraineurs may be the result of recurrent headache. Cognition, memory, and learning may play an important role in the chronification of migraines. Reducing migraine attacks has the promise of preventing chronicity of migraine.

Inhibition of toll-like receptor 4 alleviates hyperalgesia induced by acute dural inflammation in experimental migraine

Objective Although nociceptive sensitisation is an important pathophysiological process in migraine and migraine chronification, its underlying mechanisms remain unclear. Toll-like receptor 4 (TLR4), a pattern-recognition molecule, has a critical role in both neuropathic pain and morphine tolerance. The present study examined whether elements of the TLR4 pathway contribute to hyperalgesia induced by dural inflammation in rats. Methods A rat model of migraine was established by infusing a dural inflammatory soup. A group pretreated with TAK-242 was used to inhibit the activation of TLR4. The protein levels of TLR4 and its downstream molecules in the trigeminal pathway were examined by Western blot and immunofluorescence. The expression of activated microglia and astrocytes was also analysed. Levels of interleukin-1 beta, tumour necrosis factor-alpha, and brain-derived neurotrophic factor were measured by enzyme-linked immunosorbent assay. Results Acute inflammatory soup infusion induced time-dependent facial mechanical hyperalgesia, which was blocked by TAK-242 pretreatment. The inflammatory soup stimulus increased the production of TLR4 downstream molecules and interleukin-1 beta. Higher levels of microglia activation and brain-derived neurotrophic factor release were observed following the administration of the inflammatory soup but were alleviated by TAK-242. Conclusions These data suggest that the TLR4 signalling pathway promotes hyperalgesia induced by acute inflammatory soup delivery by stimulating the production of proinflammatory cytokines and activating microglia.

Characterization of migraineurs presenting interictal widespread pressure hyperalgesia identified using a tender point count: a cross-sectional study

BACKGROUND

Migraineurs exhibit pain hypersensitivity throughout the body during and between migraine headaches. Migraine is classified as a central sensitivity syndrome, typified by fibromyalgia showing widespread pressure hyperalgesia determined by a tender point. This study was performed to examine whether: 1) there is a subgroup of episodic migraineurs with widespread pressure hyperalgesia during and between attacks; 2) if such a subgroup exists, what is the prevalence and what is the difference between groups with interictal widespread hyperalgesia and acute allodynia regarding the demographic and clinical characteristics of migraine.

METHODS

This was a cross-sectional study. A total of 176 consecutive episodic migraineurs and 132 age- and sex-matched controls were recruited. The presence of widespread pressure hyperalgesia was investigated using manual tender point survey. To classify a subject's response as widespread pressure hyperalgesia, the cutoff value for responders was defined as the positive tender point count below which 95% of controls responded.

RESULTS

Based on the number of positive tender points in controls, the cutoff value of tender point count for pressure hyperalgesia responders was 7. Of the 176 subjects, interictal widespread pressure hyperalgesia and acute allodynia were observed in 74 (42%) and 115 (65.3%) patients, respectively. Univariate analysis indicated that risk factors associated with interictal widespread pressure hyperalgesia were female gender, younger age at migraine onset, higher frequency of migraine attacks, severe headache impact, cutaneous allodynia and depression. Multivariate logistic regression analysis confirmed that independent risk factors associated with interictal widespread pressure hyperalgesia were female gender, higher frequency of migraine attack and younger age at onset.

CONCLUSION

Interictal widespread pressure hyperalgesia was common (42%) in the episodic migraineurs and was associated with younger age at onset, female gender, and higher frequency of headache, but not duration of migraine illness. Presence of interictal widespread pressure hyperalgesia is assumed to be an indicator of genetic susceptibility to migraine attacks. We expect that a tender point count, as an alternative to quantitative sensory testing, will become useful as a diagnostic indicator of interictal hyperalgesia in migraineurs to predict susceptibility to migraine attacks and to permit tailored treatment.

Anti-migraine effect of ∆9-tetrahydrocannabinol in the female rat

Current anti-migraine treatments have limited efficacy and many side effects. Although anecdotal evidence suggests that marijuana is useful for migraine, this hypothesis has not been tested in a controlled experiment. Thus, the present study tested whether administration of ∆⁹-tetrahydrocannabinol (THC) produces anti-migraine effects in the female rat. Microinjection of the TRPA1 agonist allyl isothiocyanate (AITC) onto the dura mater produced migraine-like pain for 3h as measured by depression of home cage wheel running. Concurrent systemic administration of 0.32 but not 0.1mg/kg of THC prevented AITC-induced depression of wheel running. However, 0.32mg/kg was ineffective when administered 90min after AITC. Administration of a higher dose of THC (1.0mg/kg) depressed wheel running whether rats were injected with AITC or not. Administration of a CB₁, but not a CB₂, receptor antagonist attenuated the anti-migraine effect of THC. These data suggest that: 1) THC reduces migraine-like pain when administered at the right dose (0.32mg/kg) and time (immediately after AITC); 2) THC's anti-migraine effect is mediated by CB₁ receptors; and 3) Wheel running is an effective method to assess migraine treatments because only treatments producing antinociception without disruptive side effects will restore normal activity. These findings support anecdotal evidence for the use of cannabinoids as a treatment for migraine in humans and implicate the CB₁ receptor as a therapeutic target for migraine.

Identification of Allodynic Migraine Patients with the Turkish Version of the Allodynia Symptom Checklist: Reliability and Consistency Study

INTRODUCTION

Cutaneous allodynia is regarded as an expression of central sensitization in migraine. Although the gold standard is quantitative sensory testing, several practical assessment questionnaires have been developed to assess allodynia in migraine. We aimed to establish the first valid Turkish allodynia assessment questionnaire based on a 12-item allodynia symptom checklist and to evaluate the associated factors.

METHODS

The first part of the study included the translation and cultural adaptation of a Turkish version of the checklist. The Turkish version of the questionnaire was administered to 344 episodic and chronic migraine patients, who were chosen according to the International Classification of Headache Disorders -III beta criteria.

RESULTS

The total checklist score showed excellent test-retest reliability (r=0.821). The internal consistency of the checklist was assessed using Cronbach alpha values and was found to be acceptable (Cronbach alpha for the checklist=0.767). Data analysis revealed that 10 items of the questionnaire adequately identified allodynic subjects. Cutaneous allodynia was present in 218 (63.4%) migraine patients. Allodynia was more prominent in patients experiencing migraine with aura (p=0.008) and in females (p<0.001). Multiple logistic regression analysis found that female gender, aura existence, longer headache duration, and higher attack frequency were the major determinants of cutaneous allodynia.

CONCLUSION

Allodynia is common and has clinical significance in migraine; therefore, establishing a validated Turkish questionnaire for the assessment of allodynia was necessary. In this study, a Turkish version of the allodynia symptom checklist was validated and found to be convenient for the identification of allodynia in migraine patients.

Allodynia Is Associated With Initial and Sustained Response to Acute Migraine Treatment: Results from the American Migraine Prevalence and Prevention Study

OBJECTIVE

In a population sample of persons with migraine treating with a single category of acute migraine medication, to identify rates and factors associated with acute treatment outcomes, including 2-hour pain freedom (2hPF), 24-hour pain response (24hPR), and 24-hour sustained pain response (24hSPR). Key predictors include acute treatment type (triptans and other medication categories), the influence of allodynia on response to medication, and the interaction between medication category and presence of allodynia in response to treatment among people with migraine.

BACKGROUND

Cutaneous allodynia was previously associated with inadequate 2hPF, 24hPR, and 24hSPR (sustained response at 24 hours among those with adequate 2hPF) among people with migraine in the American Migraine Prevalence and Prevention (AMPP) Study.

METHODS

The AMPP Study obtained data from a representative US sample of persons with migraine by mailed questionnaire. The 2006 survey included 8233 people with migraine aged 18 or over who completed the Migraine Treatment Optimization Questionnaire (mTOQ). mTOQ was used to assess acute treatment outcomes including 2hPF, 24hPR, and 24hSPR. Eligible individuals used only a single category of acute prescription migraine treatments (n  =  5236, 63.6%). This sample was stratified into 5 categories of type of acute prescription headache medication used (triptans, nonsteroidal anti-inflammatory drugs, barbiturate-combinations, opioids, and opioid combinations and ergot alkaloids). Separate binary logistic regression models evaluated: (1) triptans vs other medication types; (2) presence of allodynia vs no allodynia; and (3) the interaction of medication category with allodynia. Sociodemographic variables, health insurance status, over-the-counter and preventive medication use were included as covariates. Odds ratios (OR) and 95% confidence intervals (CI) were generated for each acute treatment outcome.

RESULTS

Among eligible participants, the mean age was 46 years, and 82.5% were women. The triptan use group had better outcomes than other medication groups for 2hPF (OR range: 2.00-2.63, all significant except ergot alkaloids) and 24hPR (OR range: 2.10-6.22, all significant). No significant medication effects were found for the 24hSPR outcome. The presence of allodynia was associated with significantly worse outcomes for both 2hPF (OR range: 1.42-1.55, all significant) and 24hPR (OR range: 1.30-1.32, all significant, except for ergot alkaloids, P  =  .051). Allodynia effects were not significant for the 24hSPR. The interaction between medication and allodynia was also not significant (OR range for 2hPF: .68-2.02; OR range for 2hPR: .35-1.34; OR range for 24hSPR: 1.21-2.72) in any of the models, suggesting allodynia is an important predictor of treatment response regardless of the medication group prescribed.

CONCLUSIONS

The use of triptan medication was associated with significantly better 2hPF (except vs ergot alkaloids) and significantly better 24hPR outcomes compared with other acute medication categories. The presence of allodynia significantly increased the likelihood of an inadequate treatment response for both of these outcomes. Triptan use was generally associated with the best outcomes. Because allodynia was associated with inadequate outcomes for all medication groups, we suggest that allodynia is an area of unmet treatment need.

The effects of repeated nitroglycerin administrations in rats; modeling migraine-related endpoints and chronification

BACKGROUND

Rodent models typically use a single nitroglycerin injection to induce migraine, yet migraine in clinical populations presents as recurrent episodes. Further, these models quantify behavioral endpoints that do not align with the clinical features of episodic migraine or migraine chronification and therefore may limit translational relevance.

NEW METHOD

Rats received 5 nitroglycerin (10mg/kg/2ml), propylene glycol/ethanol vehicle, or saline injections every third day over 15days. Behavioral endpoints were assessed 110min post nitroglycerin administration and included time spent light/dark chambers for photophobia as well as activity, facial pain expressions, and tactile allodynia.

RESULTS

Animals administered nitroglycerin displayed photophobia, decreased activity, and increased facial pain expression. Similar alterations in photophobia and activity were seen in the vehicle treated animals, but these tended to diminish by the 4th or 5th injection. The presentation of spontaneous tactile allodynia was observed in the nitroglycerin group by the 5th episode.

COMPARISON WITH EXISTING METHODS

Most NTG migraine models entail a single NTG administration and quantification of evoked allodynia. This paradigm employs recurring NTG episodes and clinically-relevant measures of photophobia, hypoactivity and facial grimace endpoints as well as introduces a novel arena apparatus to quantify spontaneous allodynia.

CONCLUSIONS

This repeated NTG procedure and endpoint measures aligns with the frequency and clinical presentation of episodic migraine and its chronification, respectively. Further, propylene glycol ethanol vehicle contributes to migraine endpoints.

Characterization of Migraineurs Having Allodynia: Results of a Large Population-based Study

OBJECTIVE

Allodynia reflects the clinical correlate of central sensitization, but it is usually neglected in clinical headache management. We aimed to report the prevalence and previously unnoticed associations of allodynia in migraineurs by a nationwide face-to-face questionnaire-based study by physicians.

METHODS

A total of 5323 households were examined for headache according to the diagnostic criteria of International Classification of Headache Disorders-II. Detailed headache features, premonitory signs, demographics, socio-economic status, and hormonal status of female individuals were analyzed with regard to the presence of allodynia in patients with definite migraine.

RESULTS

Allodynia was present in 61.1% of migraineurs in the general population of Turkey. The duration and severity of attacks (P<0.0001), photophobia (P=0.001), phonophobia, and also osmophobia (P<0.0001), as well as premonitory signs (P=0.018), showed significant associations with allodynia. Migraineurs with aura or family history of migraine more often reported allodynia in comparison with those without (P=0.001 and 0.028, respectively). Allodynic migraineurs had a higher rate of physician consults and high levels on the Migraine Disability Assessment questionnaire, reflecting increased burden of headache. Furthermore, migraineurs with allodynia had high probability of attacks close to menses. Migraine improved during pregnancy, but it worsened after menopause or during oral contraceptive use in individuals experiencing allodynia when compared with those without allodynia.

DISCUSSION

The duration, severity, and disability of migraine attacks, photophobia, phonophobia, and osmophobia, as well as premonitory signs, showed significant associations with allodynia in the general population. Moreover, migraineurs with aura or family history of migraine more often reported allodynia, and allodynic migraneurs were more sensitive to hormonal changes. Allodynia, which seems to indicate higher tendency to central sensitization, should be implemented in daily headache practice to predict the prognosis and high levels of migraineous involvement.

Depression of home cage wheel running: a reliable and clinically relevant method to assess migraine pain in rats

BACKGROUND

The development of new anti-migraine treatments is limited by the difficulty inassessing migraine pain in laboratory animals. Depression of activity is one of the few diagnostic criteria formigraine that can be mimicked in rats. The goal of the present study was to test the hypothesis thatdepression of home cage wheel running is a reliable and clinically relevant method to assess migraine painin rats.

METHODS

Adult female rats were implanted with a cannula to inject allyl isothiocyanate (AITC) onto the dura to induce migraine pain, as has been shown before. Rats recovered from implantation surgery for 8 days in cages containing a running wheel. Home cage wheel running was recorded 23 h a day. AITC and the migraine medication sumatriptan were administered in the hour prior to onset of the dark phase.

RESULTS

Administration of AITC caused a concentration-dependent decrease in wheel running that lasted 3 h. The duration and magnitude of AITC-induced depression of wheel running was consistent following three repeated injections spaced 48 h apart. Administration of sumatriptan attenuated AITC-induced depressionof wheel running when a large dose (1 mg/kg) was administered immediately following AITC administration. Wheel running patterns did not change when sumatriptan was given to naïve rats.

CONCLUSIONS

These data indicate that home cage wheel running is a sensitive, reliable, and clinically relevant method to assess migraine pain in the rat.

Deficient prepulse inhibition of blink reflex in migraine and its relation to allodynia

OBJECTIVE

Prepulse inhibition (PPI) of the blink reflex (BR) is a reduction in BR excitability due to a conditioning stimulus, reflecting sensory gating by brainstem structures. We aimed to analyze PPI changes during a painful episode in chronic or episodic migraine and its relation to allodynia, since abnormal brainstem filtering has been hypothesized in migraine pathophysiology.

METHODS

We included 20 patients with migraine during headache episode, and age- and gender-matched 22 healthy subjects. We recorded BR after unconditioned and conditioned supraorbital stimuli. For conditioned stimuli, we applied preceding subthreshold stimulus to the median nerve at wrist. The presence of PPI was compared between the two groups, as well as the specific BR parameters (latency, amplitude or area of R1 and R2 components) in unconditioned (test) and conditioned (PPI) paradigms.

RESULTS

In the patient group, seven (35%) patients did not have R2-PPI whereas all healthy subjects had R2-PPI (P=0.003). Healthy subjects displayed significantly increased R1 amplitude and reduced R2 amplitude and area after conditioned stimuli. In migraine patients, we observed significant reduction only in R2 amplitude. Logistic regression demonstrated that allodynia was independently related with the presence of PPI (beta: -0.535, P=0.021).

CONCLUSIONS

Our study provides evidence for sensory gating impairment at brainstem level in migraine headache, related to the presence of allodynia.

Myofascial Trigger Points, Neck Mobility and Forward Head Posture in Unilateral Migraine

This paper describes the differences in the presence of myofascial trigger points (TrPs) in the upper trapezius, sternocleidomastoid, temporalis and suboccipital muscles between unilateral migraine subjects and healthy controls, and the differences in the presence of TrPs between the symptomatic side and the nonsymptomatic side in migraine subjects. In addition, we assess the differences in the presence of both forward head posture (FHP) and active neck mobility between migraine subjects and healthy controls and the relationship between FHP and neck mobility. Twenty subjects with unilateral migraine without side-shift and 20 matched controls participated. TrPs were identified when there was a hypersensible tender spot in a palpable taut band, local twitch response elicited by the snapping palpation of the taut band and reproduction of the referred pain typical of each TrP. Side-view pictures were taken in both sitting and standing positions to measure the cranio-vertebral angle. A cervical goniometer was employed to measure neck mobility. Migraine subjects showed a significantly greater number of active TrPs ( P < 0.001), but not latent TrPs, than healthy controls. Active TrPs were mostly located ipsilateral to migraine headaches ( P < 0.01). Migraine subjects showed a smaller cranio-vertebral angle than controls ( P < 0.001), thus presenting a greater FHP. Neck mobility in migraine subjects was less than in controls only for extension ( P = 0.02) and the total range of motion in flexion/extension ( P = 0.01). However, there was a positive correlation between the cranio-vertebral angle and neck mobility. Nociceptive inputs from TrPs in head and neck muscles may produce continuous afferent bombardment of the trigeminal nerve nucleus caudalis and, thence, activation of the trigeminovascular system. Active TrPs located ipsilateral to migraine headaches might be a contributing factor in the initiation or perpetuation of migraine.

Prevalence of Fibromyalgia Syndrome in Migraine Patients

Fibromyalgia syndrome (FMS) is a chronic pain syndrome of unknown aetiology characterized by diffuse pain over more than 3 months and tenderness in specific sites named tender points. The aim of this study was to assess the prevalence and severity of FMS among patients suffering from episodic migraine. Ninety-two consecutive patients (20 male, 72 female) fulfilling the International Headache Society criteria for migraine with and without aura from a tertiary headache clinic were evaluated. A headache and generalized pain history was recorded, tender points were evaluated by thumb palpation. The diagnosis of FMS was made based on the 1990 American College of Rheumatology classification criteria for FMS. Sixteen (22.2%) of the female patients and none of the male patients were diagnosed as suffering from FMS. Migraine severity and characteristics were similar to other female migraine patients. Patients suffering from migraine-FMS had lower quality of life scores and higher levels of mental distress. A high incidence of FMS was found among female migraine patients but not in males. The coexistence of FMS should be considered when choosing a prophylactic migraine therapy.

Quantitative Sensory Testing in Cluster Headache: Increased Sensory Thresholds

To determine if recently reported changes in sensory thresholds during migraine attacks can also be seen in cluster headache (CH), we performed quantitative sensory testing (QST) in 10 healthy subjects and in 16 patients with CH. Eight of the patients had an episodic CH and the other eight a chronic CH. The tests were performed on the right and left cheeks and on the right and left side of the back of the hands to determine the subjects' perception and pain thresholds for thermal (use of a thermode) and mechanical (vibration, pressure pain thresholds, pin prick, von Frey hairs) stimuli. Six patients were examined in the attack-free period. Three were also willing to repeat the tests a second time during an acute headache attack, which was elicited with nitroglycerin. The healthy subjects performed the experiments in the morning and evening of the same day to determine if sensory thresholds are independent of the time of day. If they were, this would allow estimation of the influence of the endogenous cortisone concentration on these thresholds. The control group showed no influence of the time of day on the thresholds. There was a significant difference in pain sensitivity between the back of the hands and the cheeks ( P < 0.05): higher thresholds were found on the back of the hands. The thresholds generally exhibited little intersubject variability, indicating that QST is a reliable method. There was also a significant difference between the test areas in the patient group ( P < 0.001): the cheeks were also more sensitive than the back of the hands. In comparison with reference data of healthy volunteers, the detection thresholds were increased in the patients on both test areas. These were statistically significant for warmth, thermal sensory limen (TSL), heat and pressure on the back of the hands ( P < 0.04) and for the warmth and TSL thresholds on the cheeks ( P < 0.05). There were no differences in the thresholds regardless of whether the patients were examined in or outside of a cluster bout. Furthermore, we found no cutaneous allodynia in the three patients tested during an attack. The increased sensory thresholds on the cheeks as well as on the back of the hands are in agreement with an increased activation of the patients' antinociceptive system. The seasonal variation and the temporal regularity of single attacks as well as the findings in imaging studies indicate that the hypothalamus is involved in the pathophysiology of CH. In view of the strong connectivity between the hypothalamus and areas involved in the antinociceptive system in the brainstem, we hypothesize that this connection is the reason for the increased sensory thresholds in CH patients found in our study.