General trigeminospinal central sensitization and impaired descending pain inhibitory controls contribute to migraine progression

Cilostazol induces C-fos expression in the trigeminal nucleus caudalis and behavioural changes suggestive of headache with the migraine-like feature photophobia in female rats

Introduction

Research in development of new migraine therapeutics is hindered by the lack of suitable, predictive animal models. Cilostazol provokes headache in healthy humans and migraineurs by increasing intracellular cAMP levels. We aimed to investigate whether cilostazol could provoke headache-like behaviours and c-fos expression in rats. In order to evaluate the predictive validity of the model, we examined the response to the migraine specific drug sumatriptan.

Methods

The effect of cilostazol (125 mg/kg p.o.) in female Sprague Dawley rats was evaluated on a range of spontaneous behavioural parameters, light sensitivity and mechanical sensitivity thresholds. We also measured c-fos expression in the trigeminal nucleus caudalis.

Results

Cilostazol increased light sensitivity and grooming behaviour. These manifestations were not inhibited by sumatriptan. Cilostazol also induced c-fos expression in the trigeminal nucleus caudalis. Furthermore, trigeminal – but not hind paw hyperalgesia was observed.

Conclusion

The altered behaviours are suggestive of cilostazol induced headache with migraine-like features, but not specific. The presence of head specific hyperalgesia and the c-fos response in the trigeminal nucleus caudalis imply that the model involves trigeminal nociception. The model will be useful for studying mechanisms related to the cAMP pathway in headache, but its predictive properties appear to be more limited due to the lack of response to sumatriptan.

The Chemokine Receptor CXCR2 Supports Nociceptive Sensitization after Traumatic Brain Injury

Abstract

Chronic pain after traumatic brain injury (TBI) is very common, but the mechanisms linking TBI to pain and the pain-related interactions of TBI with peripheral injuries are poorly understood. Chemokine receptors play an important role in both pain and brain injury. In the current work, we pursued the hypothesis that the epigenetically regulated CXC chemokine receptor 2 (CXCR2) is a crucial modulator of nociceptive sensitization induced by TBI. For these studies, we used the rat lateral fluid percussion model of TBI. Histone actyltransferase activity was blocked using anacardic acid beginning immediately following injury, or delayed for seven days prior to administration. The selective CXCR2 antagonist SCH527123 administered systemically or intrathecally was used to probe the role of chemokine signaling on mechanical hindpaw sensitization after TBI. The expression of the CXCR2 receptor was accomplished using real-time PCR, immunohistochemistry, and Western blotting, while epigenetic regulation was assessed using chromatin immunoprecipitation assay. The spinal levels of several pain-related mediators including CXCL1, an endogenous ligand for CXCR2, as well as brain-derived neurotrophic factor and prodynorphin were measured by enzyme-linked immunosorbent assay. We observed that anacardic acid potently blocked and reversed mechanical hindpaw sensitization after TBI. The same drug was able to prevent the upregulation of CXCR2 after TBI, but did not affect the spinal expression of other pain mediators. On the other hand, both systemically and intrathecally administered SCH527123 reversed hindpaw allodynia after TBI. Most of the spinal CXCR2 appeared to be expressed by spinal cord neurons. Chromatin immunoprecipitation experiments demonstrated TBI-enhanced association of the CXCR2 promoter with acetylated-H3K9 histone protein that was also reversible using anacardic acid. Taken together, our findings suggested that TBI causes the upregulation of spinal CXCR2 through an epigenetic mechanism ultimately supporting nociceptive sensitization. The use of CXCR2 antagonists may, therefore, be useful in pain resulting from TBI.

Trigeminal nervous system sensitization by infraorbital nerve injury enhances responses in a migraine model

Background

Although the peripheral and central sensitizations of trigeminal nervous system may be one of the important factors of migraine, the precise mechanism is not fully understood. In this study, we examined the influence of the sensitization of the second division of the trigeminal nerve (V2) by chronic constriction injury (CCI) of the infraorbital nerve (ION) on migraine headache, using the capsaicin-induced migraine model.

Methods

Male Sprague-Dawley rats were assigned to four groups: (a) sham surgery and topical-dural vehicle application (Sham + Vehicle) group, (b) CCI-ION and topical-dural vehicle application (CCI-ION + Vehicle) group, (c) sham surgery and topical-dural capsaicin application (Sham + Capsaicin) group, (d) CCI-ION and topical-dural capsaicin application (CCI-ION + Capsaicin) group. Behavioral testing and immunohistochemical staining were performed.

Results

In the behavioral test, the Sham + Capsaicin group showed significantly longer duration of immobilization and shorter duration of exploration compared with the Sham + Vehicle group, which is similar to clinical features of migraine patients. Moreover, CCI-ION enhanced these effects in the CCI-ION + Capsaicin group. Immunohistochemical staining for phospho-extracellular signal-related kinase (pERK) in the trigeminal ganglion (TG) containing first and second divisions of the trigeminal nerve and the trigeminocervical complex (TCC) revealed that pERK expression was significantly increased in the CCI-ION + Capsaicin group compared with the other groups. However, comparing between effects of the peripheral and central sensitizations (in the TG and TCC), from our results, peripheral sensitization would play a much less or not significant role.

Conclusions

These data demonstrate that the sensitization of V2 could influence the activation and the sensitization of the first division of the trigeminal nerve in the TCC, subsequently exacerbating pain sensation and pain-related behaviors. We have shown for the first time that the existence of the central sensitization of V2 can be an exacerbating factor for migraine related nociceptive thresholds/activation.

Different processing of meningeal and cutaneous pain information in the spinal trigeminal nucleus caudalis

Introduction

Within superficial trigeminal nucleus caudalis (Sp5C) (laminae I/II), meningeal primary afferents project exclusively to lamina I, whereas nociceptive cutaneous ones distribute in both lamina I and outer lamina II. Whether such a relative absence of meningeal inputs to lamina II represents a fundamental difference from cutaneous pathways in the central processing of sensory information is still unknown.

Methods

We recorded extracellular field potentials in the superficial Sp5C of anesthetised rats evoked by electrically stimulating the dura mater, to selectively assess the synaptic transmission between meningeal primary afferents and second-order Sp5C neurons, the first synapse in trigeminovascular pathways. We tested the effect of systemic morphine and local glycinergic and GABAAergic disinhibition.

Results

Meningeal stimulation evokes two negative field potentials in superficial Sp5C. The conduction velocities of the activated primary afferents are within the Aδ- and C-fibre ranges. Systemic morphine specifically suppresses meningeal C-fibre-evoked field potentials, and this effect is reversed by systemic naloxone. Segmental glycinergic or GABAAergic disinhibition strongly potentiates meningeal C-fibre-evoked field potentials but not Aδ-fibre ones. Interestingly, the same segmental disinhibition conversely potentiates cutaneous Aδ-fibre-evoked field potentials and suppresses C-fibre ones.

Conclusion

These findings reveal that the different anatomical organization of meningeal and cutaneous inputs into superficial Sp5C is associated with a different central processing of meningeal and cutaneous pain information within Sp5C. Moreover, they suggest that the potentiation upon local disinhibition of the first synapse in trigeminovascular pathways may contribute to the generation of headache pain.

High Frequency Migraine Is Associated with Lower Acute Pain Sensitivity and Abnormal Insula Activity Related to Migraine Pain Intensity, Attack Frequency, and Pain Catastrophizing

Migraine is a pain disorder associated with abnormal brain structure and function, yet the effect of migraine on acute pain processing remains unclear. It also remains unclear whether altered pain-related brain responses and related structural changes are associated with clinical migraine characteristics. Using fMRI and three levels of thermal stimuli (non-painful, mildly painful, and moderately painful), we compared whole-brain activity between 14 migraine patients and 14 matched controls. Although, there were no significant differences in pain thresholds nor in pre-scan pain ratings to mildly painful thermal stimuli, patients did have aberrant suprathreshold nociceptive processing. Brain imaging showed that, compared to controls, patients had reduced activity in pain modulatory regions including left dorsolateral prefrontal, posterior parietal, and middle temporal cortices and, at a lower-threshold, greater activation in the right mid-insula to moderate pain vs. mild pain. We also found that pain-related activity in the insula was associated with clinical variables in patients, including associations between: bilateral anterior insula and pain catastrophizing (PCS); bilateral anterior insula and contralateral posterior insula and migraine pain intensity; and bilateral posterior insula and migraine frequency at a lower-threshold. PCS and migraine pain intensity were also negatively associated with activity in midline regions including posterior cingulate and medial prefrontal cortices. Diffusion tensor imaging revealed a negative correlation between fractional anisotropy (a measure of white matter integrity; FA) and migraine duration in the right mid-insula and a positive correlation between left mid-insula FA and PCS. In sum, while patients showed lower sensitivity to acute noxious stimuli, the neuroimaging findings suggest enhanced nociceptive processing and significantly disrupted modulatory networks, particularly involving the insula, associated with indices of disease severity in migraine.

Expression of artemin and GFRα3 in an animal model of migraine: possible role in the pathogenesis of this disorder

BACKGROUND

Neurotrophic factors have been implicated in hyperalgesia and peripheral levels of these molecules are altered in migraine pathophysiology. Artemin, a vasculature-derived neurotrophic factor, contributes to pain modulation and trigeminal primary afferent sensitization through binding its selective receptor GFRα3. The distribution of artemin and GFRα3 in the dura mater raises an anatomy supports that they may be involved in migraine. In this study we evaluated the expression of artemin and GFRα3 in an animal migraine model that may be relevant for migraine.

METHODS

In this study, using a rat migraine model by administration of nitroglycerin (NTG), we investigated the expression of artemin in the dura mater and GFRα3 in the trigeminal ganglia (TG) by means of quantitative reverse transcription-polymerase chain reaction, western blot and immunofluorescence labeling.

RESULTS

Artemin immunoreactivity was found in the smooth muscle cells of dural vasculature and GFRα3 was present in cytoplasm of TG neurons. The mRNA levels of artemin and GFRα3 were significantly elevated after NTG treatment at 2 and 4 h respectively (P < 0.05). The expression of artemin protein was increased at 4 h and continually up to 8 h in the dura mater following NTG administration (P < 0.05). The expression of GFRα3 protein was elevated at 4 h and continually up to 10 h in the TG following NTG administration (P < 0.05).

CONCLUSION

The findings suggest that artemin and GFRα3 play an important role in the pathogenesis of migraine and may represent potential therapeutic targets for the treatment of migraine.

A Framework for Understanding the Relationship between Descending Pain Modulation, Motor Corticospinal, and Neuroplasticity Regulation Systems in Chronic Myofascial Pain

Myofascial pain syndrome (MPS) is a leading cause of chronic musculoskeletal pain. However, its neurobiological mechanisms are not entirely elucidated. Given the complex interaction between the networks involved in pain process, our approach, to providing insights into the neural mechanisms of pain, was to investigate the relationship between neurophysiological, neurochemical and clinical outcomes such as corticospinal excitability. Recent evidence has demonstrated that three neural systems are affected in chronic pain: (i) motor corticospinal system; (ii) internal descending pain modulation system; and (iii) the system regulating neuroplasticity. In this cross-sectional study, we aimed to examine the relationship between these three central systems in patients with chronic MPS of whom do/do not respond to the Conditioned Pain Modulation Task (CPM-task). The CPM-task was to immerse her non-dominant hand in cold water (0-1°C) to produce a heterotopic nociceptive stimulus. Corticospinal excitability was the primary outcome; specifically, the motor evoked potential (MEP) and intracortical facilitation (ICF) as assessed by transcranial magnetic stimulation (TMS). Secondary outcomes were the cortical excitability parameters [current silent period (CSP) and short intracortical inhibition (SICI)], serum brain-derived neurotrophic factor (BDNF), heat pain threshold (HPT), and the disability related to pain (DRP). We included 33 women, (18-65 years old). The MANCOVA model using Bonferroni's Multiple Comparison Test revealed that non-responders (n = 10) compared to responders (n = 23) presented increased intracortical facilitation (ICF; mean ± SD) 1.43 (0.3) vs. 1.11 (0.12), greater motor-evoked potential amplitude (μV) 1.93 (0.54) vs. 1.40 (0.27), as well a higher serum BDNF (pg/Ml) 32.56 (9.95) vs. 25.59 (10.24), (P < 0.05 for all). Also, non-responders presented a higher level of DRP and decreased HPT (P < 0.05 for all). These findings suggest that the loss of net descending pain inhibition was associated with an increase in ICF, serum BDNF levels, and DRP. We propose a framework to explain the relationship and potential directionality of these factors. In this framework we hypothesize that increased central sensitization leads to a loss of descending pain inhibition that triggers compensatory mechanisms as shown by increased motor cortical excitability.

Diagnosis and treatment for chronic migraine

Migraine is a debilitating headache disorder that is underdiagnosed and undertreated worldwide, partially attributable to misdiagnosis and expectations of poor treatment outcomes. This article provides a review of chronic migraine, including pathophysiology, burden, diagnosis, and management, with special emphasis on the role of NPs.

Migraine is a debilitating headache disorder that is underdiagnosed and undertreated worldwide, partially attributable to misdiagnosis and expectations of poor treatment outcomes. This article provides a review of chronic migraine, with special emphasis on the role of NPs.

Empirically Supported Use of Psychiatric Medications in Adolescents and Adults with IBD

BACKGROUND

The use of psychotropic medications, particularly antidepressants, is common in patients with inflammatory bowel disease (IBD) in spite of a lack of their robust efficacy in this population. This review provides an overview of the use trends of different classes of antidepressant and anti-anxiety medication and their effects on mood, nervous system function, gastrointestinal physiology and immunity drawing from the literature available in the general population, other medical conditions, and when available, patients with IBD. It also covers the evidence base for the actions, efficacy, and potential complications of antidepressants organized by different classes.

METHODS

We conducted a PubMed search of articles relating the different drug classes probed to the terms above in different populations of interest. All types of articles were accepted including case reports and series, open and randomized trials, reviews, and expert opinion. We also examined the reference lists of the publications found.

RESULTS

Selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) are the most commonly prescribed agents for anxiety and depression in patients with IBD, though their efficacy for these conditions in the general population are mild to moderate at best. SSRIs are generally well tolerated, though at higher doses, they, like most antidepressant classes, can be associated with activation, serotonergic syndrome, and increased suicidal ideation. TCAs have many more serious side effects but have some shown efficacy for functional GI symptoms. A newer class, the serotonin noradrenergic reuptake inhibitors (SNRIs), can be effective for refractory depression, anxiety and chronic pain syndromes with a side effect profile similar to both SSRIs and more mild manifestations of TCAs. Mirtazapine has moderate efficacy for depression if sedation and weight gain side effects are tolerated and some small support for use in nausea and vomiting. Bupropion targets dopamine and noradrenaline reuptake and has moderate efficacy for depression, and some small support for use in fatigue and smoking cessation. Buspirone has an indication for generalized anxiety disorder though studies show only a minimal benefit. It has some growing evidence for use in functional dyspepsia. Most of these agents have physiological effects on the brain, immune system, and gastrointestinal tract (with the exception of bupropion) hence their therapeutic and side effects manifested in these systems.

CONCLUSION

Antidepressant medications are frequently prescribed for depression, anxiety disorders, and chronic pain syndromes, but overall support for their efficacy is modest at best. Psychological interventions have growing support for having much more robust effects without the side effects of antidepressants and should be considered first-line treatment or at least an adjunct to psychotropic medications for these conditions.

Functional interictal changes of pain processing in migraine with ictal cutaneous allodynia

Objective

A prospective clinical imaging study has been conducted to investigate pain processing functional pathways during trigeminal heat stimulation (THS) in patients with migraine without aura experiencing ictal cutaneous allodynia (CA) (MwoA CA+).

Methods

Using whole-brain BOLD-fMRI, functional response to THS at three different intensities (41°, 51° and 53℃) was investigated interictally in 20 adult MwoA CA+ patients compared with 20 MwoA patients without ictal CA (MwoA CA−) and 20 healthy controls (HCs). Secondary analyses evaluated associations between BOLD signal change and clinical features of migraine.

Results

During moderate-noxious THS (51℃), we observed a significantly greater activation in (a) the anterior cingulate cortex in MwoA CA+ patients compared to HCs and (b) the middle frontal gyrus in MwoA CA+ patients compared to both MwoA CA− patients and HCs. Furthermore, during high-noxious THS (53℃) a significantly decreased activation in the secondary somatosensory cortices was observed in (a) MwoA CA− patients compared to both MwoA CA+ patients and HCs and (b) MwoA CA+ patients compared to HCs. CA severity was positively correlated with the secondary somatosensory cortices activation.

Conclusions

Our findings suggest that CA may be subtended by both a dysfunctional analgesic compensatory mechanism and an abnormal internal representation of pain in migraine patients.

Effect of electroacupuncture pretreatment at GB20 on behaviour and the descending pain modulatory system in a rat model of migraine

BACKGROUND

While electroacupuncture (EA) pretreatment has been found to ameliorate migraine-like symptoms, the underlying mechanisms remain poorly understood. Emerging evidence suggests that the brainstem descending pain modulatory system, comprising the periaqueductal grey (PAG), raphe magnus nucleus (RMg), and trigeminal nucleus caudalis (TNC), may be involved in migraine pathophysiology. We hypothesised that EA would ameliorate migraine-like symptoms via modulation of this descending system.

METHODS

We used a conscious rat model of migraine induced by repeated electrical stimulation of the dura. Forty male Sprague-Dawley rats were randomly assigned to one of four groups: an EA group, which received EA at GB20 following dural stimulation; a sham acupuncture (SA) group, which received manual acupuncture at a non-acupuncture point following dural stimulation; a Model group, which received dural stimulation but no acupuncture; and a Control group, which received neither dural stimulation nor acupuncture (electrode implantation only). HomeCageScan was used to measure effects on behaviour, and immunofluorescence staining was used to examine neural activation (c-Fos immunoreactivity) in the PAG, RMg, and TNC.

RESULTS

Compared to the Model group, rats in the EA group showed a significant increase in exploratory, locomotor and eating/drinking behaviour (p<0.01) and a significant decrease in freezing-like resting and grooming behaviour (p<0.05). There was a significant increase in the mean number of c-Fos neurons in the PAG, RMg, and TNC in Model versus Control groups (p<0.001); however, this was significantly attenuated by EA treatment (p<0.001). There were no significant differences between the SA and Model groups in behaviour or c-Fos immunoreactivity.

CONCLUSIONS

EA pretreatment ameliorates behavioural changes in a rat model of recurrent migraine, possibly via modulation of the brainstem descending pathways.

A touchy subject: an assessment of cutaneous allodynia in a chronic migraine population

Background

Cutaneous allodynia (CA) is a common feature of migraine, which has a complex underlying pathophysiology that is not well understood. In addition to pain, photophobia, phonophobia, osmophobia, nausea, and vomiting, CA can contribute to the overall disability caused by migraine. The presence of CA can be established via a validated questionnaire. Validated questionnaires and other tests are rarely performed in clinical practice. As such, current prevalence estimates for CA may be an underestimation.

Methods

Utilizing a validated questionnaire, we assessed the presence of CA in consecutive patients (n=44) presenting with chronic migraine at a tertiary headache center.

Results

CA appears to be quite prevalent, at ~90%, among female patients with chronic migraine.

Conclusion

CA prevalence in chronic migraine may be underestimated in the literature, and larger studies may better demonstrate a more accurate estimate of its prevalence.

Laser-evoked potential habituation and central sensitization symptoms in childhood migraine

Objectives

Few studies have addressed central sensitization symptoms and pain processing in childhood migraine. Our aims were to examine pain sensitivity and responses, including habituation, evoked by CO2 laser stimuli (laser-evoked potentials (LEPs)) in a cohort of children with migraine compared to non-migraine controls and to determine the correlation between LEP features and signs of central sensitization.

Methods

Thirty-five patients 8–15 years of age with migraines without aura were evaluated during the inter-critical phase and were compared to 17 controls. LEPs were analyzed, and their main features were correlated with clinical symptoms including allodynia and pericranial tenderness.

Results

The laser-evoked pain threshold was lower and the N2P2 vertex complex amplitude was higher in children with migraines. Furthermore, habituation of vertex waves of LEPs clearly showed a tendency toward progressive amplitude enhancement in the migraine group. Acute allodynia and inter-critical pericranial tenderness correlated with trigeminal LEP features, particularly with the abnormal habituation pattern.

Discussion

Abnormalities of pain processing and symptoms of central sensitization appear to be characteristics of children with migraine. Reduced habituation and progressive amplification of cortical responses to laser stimuli indicate an overactive nociceptive system at the onset of migraine, and this hyperactivity may subtend allodynia and pericranial tenderness. Future prospective trials may aid in the early identification of clinical phenotypes that display a tendency to develop into the chronic form of migraine, warranting a timely therapeutic approach.

Transcutaneous supraorbital neurostimulation in "de novo" patients with migraine without aura: the first Italian experience

BACKGROUND

Transcutaneous supraorbital neurostimulation (tSNS) has been recently found superior to sham stimulation for episodic migraine prevention in a randomized trial. We evaluated both the safety and efficacy of a brief period of tSNS in a group of patients with migraine without aura (MwoA).

METHODS

We enrolled 24 consecutive patients with MwoA experiencing a low frequency of attacks, which had never taken migraine preventive drugs in the course of their life. Patients performed a high frequency tSNS and were considered "compliant" if they used the tSNS for ≥ 2/3 of the total time expected. For this reason, four patients were excluded from the final statistical analysis. Primary outcome measures were the reduction migraine attacks and migraine days per month (p < 0.05). Furthermore, we evaluated the percentage of patients having at least 50% reduction of monthly migraine attacks and migraine days. Secondary outcome measures were the reduction of headache severity during migraine attacks and HIT-6 (Headache Impact Test) rating as well as in monthly intake of rescue medication (p < 0.05). Finally, compliance and satisfaction to treatment and potential adverse effects related to tSNS have been evaluated.

RESULTS

Between run-in and second month of tSNS treatment, both primary and secondary endpoints were met. Indeed, we observed a statistically significant decrease in the frequency of migraine attacks (p < 0.001) and migraine days (p < 0.001) per month. We also demonstrated at least 50% reduction of monthly migraine attacks and migraine days in respectively 81 and 75% of patients. Furthermore, a statistically significant reduction in average of pain intensity during migraine attacks (p = 0.002) and HIT-6 rating (p < 0.001) and intake of rescue medication (p < 0.001) has been shown. All patients showed good compliance levels and no relevant adverse events.

CONCLUSION

In patients experiencing a low frequency of attacks, significant improvements in multiple migraine severity parameters were observed following a brief period of high frequency tSNS. Therefore, tSNS may be considered a valid option for the preventive treatment of migraine attacks in patients who cannot or are not willing to take daily medications, or in whom low migraine frequency and/or intensity would not require pharmacological preventive therapies.

Clinical Pain Catastrophizing in Women With Migraine and Obesity

OBJECTIVE/BACKGROUND

Obesity is related to migraine. Maladaptive pain coping strategies (eg, pain catastrophizing) may provide insight into this relationship. In women with migraine and obesity, we cross-sectionally assessed: (1) prevalence of clinical catastrophizing; (2) characteristics of those with and without clinical catastrophizing; and (3) associations of catastrophizing with headache features.

METHODS

Obese women migraineurs seeking weight loss treatment (n = 105) recorded daily migraine activity for 1 month via smartphone and completed the Pain Catastrophizing Scale (PCS). Clinical catastrophizing was defined as total PCS score ≥30. The six-item Headache Impact Test (HIT-6), 12-item Allodynia Symptom Checklist (ASC-12), Headache Management Self-Efficacy Scale (HMSE), and assessments for depression (Centers for Epidemiologic Studies Depression Scale) and anxiety (seven-item Generalized Anxiety Disorder Scale) were also administered. Using PCS scores and body mass index (BMI) as predictors in linear regression, we modeled a series of headache features (ie, headache days, HIT-6, etc) as outcomes.

RESULTS

One quarter (25.7%; 95% confidence interval [CI] = 17.2-34.1%) of participants met criteria for clinical catastrophizing: they had higher BMI (37.9 ± 7.5 vs 34.4 ± 5.7 kg/m(2) , P = .035); longer migraine attack duration (160.8 ± 145.0 vs 97.5 ± 75.2 hours/month, P = .038); higher HIT-6 scores (68.7 ± 4.6 vs 64.5 ± 3.9, P < .001); more allodynia (7.0 ± 4.1 vs 4.5 ± 3.5, P < .003), depression (25.4 ± 12.4 vs 13.3 ± 9.2, P < .001), and anxiety (11.0 ± 5.2 vs 5.6 ± 4.1, P < .001); and lower self-efficacy (80.1 ± 25.6 vs 104.7 ± 18.9, P < .001) compared with participants without clinical catastrophizing. The odds of chronic migraine were nearly fourfold greater in those with (n = 8/29.6%) vs without (n = 8/10.3%) clinical catastrophizing (odds ratio = 3.68; 95%CI = 1.22-11.10, P = .021). In all participants, higher PCS scores were related to more migraine days (β = 0.331, P = .001), longer attack duration (β = 0.390, P < .001), higher HIT-6 scores (β = 0.425, P < .001), and lower HMSE scores (β = -0.437, P < .001). Higher BMI, but not higher PCS scores, was related to more frequent attacks (β = -0.203, P = .044).

CONCLUSIONS

One quarter of participants with migraine and obesity reported clinical catastrophizing. These individuals had more frequent attacks/chronicity, longer attack duration, higher pain sensitivity, greater headache impact, and lower headache management self-efficacy. In all participants, PCS scores were related to several migraine characteristics, above and beyond the effects of obesity. Prospective studies are needed to determine sequence and mechanisms of relationships between catastrophizing, obesity, and migraine.

Sensitization of the trigeminovascular system following environmental irritant exposure

BACKGROUND

Air pollution is linked to increased emergency room visits for headache, and migraine patients frequently cite chemicals or odors as headache triggers, but the association between air pollutants and headache is not well understood. We previously reported that nasal administration of environmental irritants acutely increases meningeal blood flow via a TRPA1-dependent mechanism involving the trigeminovascular system. Here, we examine whether chronic environmental irritant exposure sensitizes the trigeminovascular system.

METHODS

Male rats were exposed to acrolein, a TRPA1 agonist, or room air by inhalation for four days prior to meningeal blood flow measurements. Some animals were injected daily with a TRPA1 antagonist, AP-18, or vehicle prior to inhalation exposure. Trigeminal ganglia were isolated following blood flow measurements for immunocytochemistry and/or qPCR determination of TRPV1, TRPA1 and CGRP levels.

RESULTS

Acrolein inhalation exposure potentiated blood flow responses both to TRPA1 and TRPV1 agonists compared to room air. Acrolein exposure did not alter TRPV1 or TRPA1 mRNA levels or TRPV1 or CGRP immunoreactive cell counts in the trigeminal ganglion. Acrolein sensitization of trigeminovascular responses to a TRPA1 agonist was attenuated by pre-treatment with AP-18.

INTERPRETATION

These results suggest trigeminovascular sensitization as a mechanism for enhanced headache susceptibility after chemical exposure.

Altered cognition-related brain activity and interactions with acute pain in migraine

Little is known about the effect of migraine on neural cognitive networks. However, cognitive dysfunction is increasingly being recognized as a comorbidity of chronic pain. Pain appears to affect cognitive ability and the function of cognitive networks over time, and decrements in cognitive function can exacerbate affective and sensory components of pain. We investigated differences in cognitive processing and pain–cognition interactions between 14 migraine patients and 14 matched healthy controls using an fMRI block-design with two levels of task difficulty and concurrent heat (painful and not painful) stimuli. Across groups, cognitive networks were recruited in response to a difficult cognitive task, and a pain–task interaction was found in the right (contralateral to pain stimulus) posterior insula (pINS), such that activity was modulated by decreasing the thermal pain stimulus or by engaging the difficult cognitive task. Migraine patients had less task-related deactivation within the left dorsolateral prefrontal cortex (DLPFC) and left dorsal anterior midcingulate cortex (aMCC) compared to controls. These regions have been reported to have decreased cortical thickness and cognitive-related deactivation within other pain populations, and are also associated with pain regulation, suggesting that the current findings may reflect altered cognitive function and top-down regulation of pain. During pain conditions, patients had decreased task-related activity, but more widespread task-related reductions in pain-related activity, compared to controls, suggesting cognitive resources may be diverted from task-related to pain-reduction-related processes in migraine. Overall, these findings suggest that migraine is associated with altered cognitive-related neural activity, which may reflect altered pain regulatory processes as well as broader functional restructuring.

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Migraine patients had blunted task-related deactivations in DLPFC, aMCC, and cerebellum in the absence of pain, vs. controls.

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Unlike in healthy controls, these task-related deactivations were not modulated by the presence of an acute pain stimulus.

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Migraine patients had less task-related activity during pain, compared to controls.

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Acute pain disturbs cognitive processing more in patients than controls.