Looking to the Future: Research Designs for Study of Headache Disease Progression

Migraine Progression: A Systematic Review

BACKGROUND

Migraine is a common and often debilitating neurological disease. It can be divided into episodic and chronic subforms based on the number of monthly headache days. Because only a subset of individuals with episodic migraine (EM) progress to chronic migraine (CM) over any given time period, understanding the factors that predict the new onset of CM or "migraine progression" may provide insights into the mechanisms, pathophysiology, prevention, and treatment of CM. In this review, we identify and summarize studies that report risk factors associated with the new onset of CM or related chronic headache diagnoses, group these risk factors and report the strength of evidence for the identified risk factors.

OBJECTIVE

To conduct a systematic review of studies that identify risk factors for the new onset of CM or related chronic headache diagnoses such as transformed migraine (TM) and chronic daily headache (CDH).

METHODS

Herein we summarize the findings of studies of risk factors associated with the new onset of CM/TM, CDH, or related diagnoses from the English language literature published before March 2018. The PubMed database was searched for relevant studies. Longitudinal studies with follow-up data and case-control studies were included in this qualitative synthesis. We report methodology, analytic criteria, and results for each manuscript and for the parent study. Next, we review the strength of evidence for each of the identified risk factors using a modified version of AB Hill's criteria for causation and rank evidence as fair, moderate, or strong. We categorized risk factors as nonmodifiable, modifiable and based on putative mechanisms. We further categorized risk factors into sociodemographics, lifestyle factors and habits, headache features, comorbid and concomitant diseases and conditions and pharmacologic treatment-related. Finally, we review theories of the pathophysiology underlying the development of new onset chronic migraine or increasing attack frequency.

RESULTS

The PubMed search yielded 1870 records after duplicates were removed. Nine additional records were identified through expert consultation and other methods (eg, citations found as references in manuscripts identified in the literature review and through communication with the authors of manuscripts included in the review). The 1879 manuscripts were screened against the inclusion and exclusion criteria and 109 were found to be potentially eligible. Of 109 full-text articles, 17 studies were identified as meeting the prespecified criteria based on the consensus of all authors. Of the 17 full texts, 13 were longitudinal cohort studies and 4 were case-controlled studies. We found strength of evidence ranging from fair to strong for the identified risk factors. The strongest data were found for increased headache day frequency, depression, and medication overuse/high-frequency use. Risk factors for new onset CM and CDH in children and adolescents were similar to those identified in adults.

CONCLUSIONS

A range of risk factors for the new onset of CM/TM, CDH, or related chronic headache diseases were identified with the strongest data supporting increased headache day frequency, acute medication overuse/high-frequency use and depression, which are potentially modifiable risk factors. Modifiable risk factors may provide targets for intervention. The lack of strong evidence or any evidence does not imply that there is not a relationship between a particular risk factor and new onset CM or related disease; but may indicate little or no research or that research did not have sufficient methodological rigor. In addition, it is likely that additional risk factors exist which have not yet been identified. Putative factors include pro-inflammatory states and pro-thrombotic states. Development of central sensitization and increased activation of the trigeminal nociceptive pathways may be drivers of the new onset of CM or CDH. Future research may include the systematic testing of interventions targeting modifiable risk factors to determine if progression can be prevented as well as continued exploration of the benefits of treating these risk factors among people with CM in an effort to increase rates of remission. Future work should also consider the natural fluctuations in headache day frequency and examine progression in terms of continuous definitions rather than or in addition to a dichotomous boundary.

A systematic literature review of observational studies of the bidirectional association between metabolic syndrome and migraine

AIMS

To evaluate all epidemiological evidence in the literature linking the metabolic syndrome (MetS) and migraine in adults.

METHODS

Database (Medline, Embase; published reports up to November 2017) and manual searches were performed. Information on data collection, sample characteristics, study design, MetS and migraine assessment, and results was extracted from each relevant publication. The methodological quality of each study was also assessed.

RESULTS

A total of 15 observational epidemiological studies in adults, published between 2009 and 2017, were retrieved. Of these, one employed a prospective design, while the rest had a cross-sectional (13 studies) or case-control (one study) design. Five studies assessed the presence of migraine in individuals with MetS, whereas 10 studies assessed the presence or risk of MetS in migraineurs. Most participants were female hospital outpatients. The sole prospective cohort study reported 11-year MetS incidence of 21.8% in migraineurs with aura, 16.8% in migraineurs without aura and 14.5% in subjects without headaches. Most studies (60%) provided no statistical estimates of association. Methodological flaws included selection biases, lack of power analysis, unsuitable research plans and no multivariable analyses. Meta-analysis was not feasible with the available data.

CONCLUSION

Our systematic review has identified major gaps in knowledge and weaknesses in research that should provide an impetus for future epidemiological investigations using more rigorous methodology, large general-population prospective cohorts, and substantial data on dietary behaviours and lifestyle.

Chronic Migraine: An Update on Physiology, Imaging, and the Mechanism of Action of Two Available Pharmacologic Therapies

Several lines of research support the hypothesis that migraine is a spectrum of illness, with clinical symptoms that vary along a continuum from episodic migraine to chronic migraine. Physiologic changes may result in episodic migraine evolving into chronic migraine over months to years in susceptible individuals. With chronification, headache frequency increases, becoming more disabling and less responsive to therapy. Neurophysiologic and functional imaging research has reported that chronic migraine may be associated with severity‐specific metabolic, functional, and structural abnormalities in the brainstem. Without longitudinal studies, it is unclear whether these changes may represent a continuum of individual progression and/or are reversible. Furthermore, chronic migraine is associated with larger impairments in cortical processing of sensory stimuli when compared with episodic migraine, possibly caused by more pronounced cortical hyperexcitability.

Progressive changes in nociceptive thresholds and subsequent central sensitization due to recurrent migraine attacks in vulnerable individuals contribute to the chronic migraine state. This may result in changes to baseline neurologic function between headache attacks, evident in both electrophysiological and functional imaging research. Patients experiencing migraine chronification may report increased non‐headache pain, fatigue, psychiatric disorders (eg, depression, anxiety), gastrointestinal complaints, and other somatic conditions associated with their long‐term experience with migraine pain.

Recent research provides a foundation for differentiating episodic and chronic migraine based on neurophysiologic and neuroimaging tools. In this literature review, we consider these findings in the context of models designed to explain the physiology and progression of episodic migraine into chronic migraine, and consider treatment of chronic migraine in susceptible individuals. Advances in pharmacotherapy provide treatment options for chronic migraine. Of the currently available treatment options, only onabotulinumtoxinA and topiramate have received regulatory approval and have demonstrated efficacy in patients with chronic migraine, although the exact mechanisms of action are not fully elucidated.

Validation of the Headache Impact Test (HIT-6) in patients with chronic migraine

Background

The Headache Impact Test (HIT)-6 was developed and has been validated in patients with various types of headache. The objective of this study was to report the psychometric properties of the HIT-6 among patients with chronic migraine.

Methods

Data came from two international, multicenter, randomized, double-blind, placebo-controlled clinical trials of chronic migraine patients (N = 1,384) undergoing prophylaxis therapy. Confirmatory factor analysis and differential item functioning (DIF) analysis were used to test the latent structure and cross-cultural comparability of the HIT-6. Reliability, construct validity, and responsiveness were assessed. Two sets of criterion groups were used: (1) 28-day headache frequency: <10, 10–14, and ≥15 days; (2) sample quartiles of the total cumulative hours of headache: <140, 140 to <280, 280 to <420, and ≥420 hours. Two sets of responsiveness categories were defined as reduction of <30%, 30% to <50%, or ≥50% in (1) number of headache days and (2) cumulative hours of headache.

Results

Measurement invariance tests supported the stability of the HIT-6 latent structure across studies. DIF analysis supported cross-cultural comparability. Good reliability was observed across studies (Cronbach’s α: 0.75–0.92; intraclass correlation coefficient: 0.76–0.80). HIT-6 scores correlated strongly (−0.86 to −0.59) with scores of the Migraine-Specific Quality-of-Life Questionnaire. Analysis of variance indicated that HIT-6 scores discriminated across both types of criterion groups (P<0.001), across studies and time points. HIT-6 change scores were significantly higher in magnitude in groups experiencing greater improvement (P<0.001).

Conclusion

All measurement properties were consistently verified across the two studies, supporting the validity of the HIT-6 among chronic migraine patients.

Trial registration

NCT00156910 and NCT00168428 on www.ClinicalTrials.gov.

Chronic migraine in women is associated with insulin resistance: a cross-sectional study

BACKGROUND AND PURPOSE

Migraine is a common neurological disorder. It can be divided into episodic migraine (EM) and chronic migraine (CM), based on headache frequency. Some studies have shown that insulin sensitivity is impaired in migraine; moreover, hypertension, diabetes and obesity are common in patients with CM. The aim of this study was to assess serum glucose, insulin levels and insulin resistance (IR) in a sample of episodic migraineurs, chronic migraineurs and non-pain healthy controls.

METHODS

Eighty-three women with EM, 83 with CM and 83 healthy controls were recruited. Headache was diagnosed according to the latest International Classification of Headache Disorders 2 criteria. Waist circumference, body mass index (BMI) and blood pressure were measured. Checked metabolic parameters included fasting glucose, the 2 h 75 g oral glucose tolerance test (2 h OGTT), serum HbA1c, blood lipid profile, C-reactive protein and prolactin. The homeostasis model assessment formula was used to calculate IR.

RESULTS

A significant prevalence of IR in CM was observed (P = 0.002). No significant associations were found with fasting glycaemia, the 2 h OGTT, HbA1c, blood lipid profile, C-reactive protein, prolactin and waist circumference. Obesity (BMI >30 kg/m(2)) was associated with an increased risk of CM [odds ratio (OR) 2.4]. When the outcome of interest was the association between IR and obesity, the OR was significantly increased compared with IR alone (OR = 13.2).

CONCLUSION

This may suggest that CM is associated with IR status, particularly when it is in partnership with obesity.

Reduced Frontal P3a Amplitude in Migraine Patients during the Pain-Free Period

BACKGROUND AND PURPOSE

Neuropsychological and neuroimaging studies both suggest that frontal lobe dysfunction is present in migraineurs. Since P3a abnormalities manifest in other diseases associated with attention problems, such as attention deficit hyperactivity disorder, we hypothesized that migraine patients have P3a abnormalities, particularly in the frontal region.

METHODS

Event-related potentials were measured using a passive auditory oddball paradigm in 16 female migraineurs (aged 22.9±2.0 years, mean±SD) during the interictal period and in 16 age-matched healthy females (22.6±2.0 years). The amplitudes and latencies were analyzed independently using repeated-measures analysis of variance. Nonparametric statistical testing using a cluster-level randomization method was performed to localize the abnormalities.

RESULTS

The mean P3a amplitude at frontal areas during the third trials was significantly lower in migraineurs (1.06 µV) than in controls (1.69 µV, p=0.026). P3a amplitudes were negatively correlated with the duration of the migraine history (r=-0.618, p=0.014). Cluster-based nonparametric statistical analysis showed that the amplitudes over left frontal areas were significantly lower in migraine patients than in controls.

CONCLUSIONS

A reduced P3a amplitude of migraineurs reflects attentional deficits and frontal dysfunction. The negative correlation between P3a amplitude and the duration of the migraine history suggests that attentional deficits and frontal dysfunction are either the cause or the result of headache.

Mechanism of chronic migraine

Chronic migraine typically evolves from episodic migraine over months to years in susceptible individuals. Headaches increase in frequency over time, becoming less intense but more disabling and less responsive to treatment. Results of electrophysiologic and functional imaging studies indicate that chronic migraine is associated with abnormalities in the brainstem that may be progressive. Additionally, chronic migraine is associated with a greater degree of impairment in cortical processing of sensory stimuli than is episodic migraine, perhaps due to a more pervasive or persistent cortical hyperexcitability. These findings fit with the model of migraine as a spectrum disorder, in which the clinical and pathophysiological features of migraine may progress over time. This progression is postulated to result from changes in nociceptive thresholds and ensuing central sensitization caused by recurrent migraine in susceptible individuals, for whom a variety of risk factors have been described. This may lead to changes in baseline neurologic function between episodes of headache, evident not only in electrophysiologic and functional imaging studies, but also as an increase in depression, anxiety, nonhead pain, fatigue, gastrointestinal disorders, and other somatic complaints that may occur after years of episodic migraine. From the current research and migraine models, a conceptualization of chronic migraine, in which relatively permanent and pervasive central changes that warrant novel and tolerable treatments have occurred, is emerging. This model also implies that prevention of chronic migraine is an important goal in the management of episodic migraine, particularly in individuals who exhibit risk factors for chronic transformation.

Chronic migraine: epidemiology and disease burden

Chronic migraine is a common and disabling complication of migraine with a population prevalence of about 2%. Emerging evidence suggests that episodic migraine and chronic migraine differ not only in degree, but also in kind. Compared with patients with episodic migraine, those with chronic migraine have worse socioeconomic status, reduced health-related quality of life, increased headache-related burden (including impairment in occupational, social, and family functioning), and greater psychiatric and medical comorbidities. Each year, approximately 2.5% of patients with episodic migraine develop new-onset chronic migraine (ie, chronification). Understanding the natural disease course, improving treatment and management, and preventing the onset could reduce the enormous individual and societal burden of chronic migraine, and thus, have become important goals of headache research. This review provides a summary of the history of nomenclature and diagnostic criteria, as well as recent studies focusing on the epidemiology, natural history, and burden of chronic migraine.

Validation of the Headache Impact Test (HIT-6™) across episodic and chronic migraine

OBJECTIVE

The purpose of this study was to assess psychometric properties of the six-item Headache Impact Text (HIT-6™) across episodic and chronic migraine.

METHODS

Using a migraine screener and number of headache days per month (HDPM), participants from the National Survey of Headache Impact (NSHI) study and the HIT-6 validation study (HIT6-V) were selected for this study. Eligible participants were categorized into three groups: chronic migraine (CM: ≥ 15 HDPM); episodic migraine (EM: < 15 HDPM); non-migraine headaches. Reliability and validity of the HIT-6 were evaluated.

RESULTS

A total of 2,049 survey participants met the inclusion/exclusion criteria for this study. Participants were identified as 6.4% CM; 42.1% EM; 51.5% non-migraine, with respective mean HIT-6 scores: 62.5 ± 7.8; 60.2 ± 6.8; and 49.1 ± 8.7. High reliability was demonstrated with internal consistency (time1/time2) of 0.83/0.87 in NSHI, and 0.82/0.92 in HIT6-V. Intra-class correlation for test-retest reliability was very good at 0.77. HIT-6 scores correlated significantly (p < .0001) with total Migraine Disability Assessment Scale scores (r = 0.56), headache pain severity (r = 0.46), and HDPM (r = 0.29). Discriminant validity analysis showed significantly different HIT-6 scores (F = 488.02, p < .0001) across the groups.

CONCLUSION

Results from these analyses confirm that the HIT-6 is a reliable and valid tool for discriminating headache impact across episodic and chronic migraine.

Greater occipital nerve block in chronic migraine

Headache syndromes often involve occipital and neck symptoms suggesting a functional connectivity between nociceptive trigeminal and cervical afferents. Several studies have suggested that pain relief in migraine and other types of headache can be achieved by local injections of steroids, local anaesthetics or a mixture of both in the area of greater occipital nerve (GON). Usually greater occipital nerve block (GONB) is performed by using local anaesthetics alone or with steroid. The rationale of performing a GONB for the treatment of chronic headache states is on the anatomical connections between trigeminal and upper cervical sensory fibres at the level of the trigeminal nucleus caudalis. However, the reason for the improvement after GONB in primary headache is unknown. The objective of this study is to determine whether adding triamcinolone to local anaesthetics increased the efficacy of GONB and trigger point injections (TPIs) for chronic migraine (TM). Patients with TM were randomized to receive GONB and TPIs using lidocaine 2% and bupivacaine 0.5% + either saline or triamcinolone 40 mg. Particularly, a 10-ml syringe containing 4.5 ml of lidocaine 2%, 4.5 ml of bupivacaine 0.5% and 1 ml of either saline (group A) or triamcinolone 40 mg/ml (group B) was prepared for each patients. Patients were given bilateral GONB and TPIs in the cervical paraspinal and trapezius muscles bilaterally. 2 ml were injected into each GON at the medial third of the distance between the occipital protuberance and the mastoid process. In addition, 0.5 ml was injected into each of the 12 trigger points. The total injected volume was 10 ml. The primary outcome measure was the change in mean headache severity from before injection to 20 min after in the two groups. Secondary outcome measures were the change in mean neck pain, photophobia and phonofobia severity from before injection to 20 min after in the two groups. Patients documented headache and severity of associated symptoms for 4 weeks after injection. Changes in symptom severity were compared between the two groups. Thirty-seven patients were included. Twenty minutes after injection, mean headache severity decreased by 3.2 points in group A (p < 0.01) and by 3.1 points in group B (p < 0.01). Mean neck pain severity decreased by 1.5 points in group A (p < 0.01) and by 1.7 points in group B (p < 0.01). Mean duration of being headache-free was 2.7 +/- 3.8 days in group A and 1.0 +/- 1.1 days in group B (p = 0.67). None of the outcome measures differed significantly between the two groups. Both treatments were full tolerated. In our study, adding triamcinolone to local anaesthetic when performing GONB and TPIs was not associated with improved outcome in the sample of patients with TM. In both groups, the procedure resulted in significant and rapid relief of headache, neck pain, photophobia and phonofobia.

Topiramate intervention to prevent transformation of episodic migraine: the topiramate INTREPID study

OBJECTIVE

The study sought to evaluate whether topiramate prevents development of chronic daily headache (CDH, ≥15 headache days per month) in adult subjects with high-frequency episodic migraine (HFEM, 9-14 migraine headache days/month). A secondary objective was to assess the efficacy of topiramate as preventive migraine treatment in this population.

METHODS

This was a multicenter, randomized, double-blind, placebo-controlled study comparing topiramate 100 mg/day and placebo for 26 weeks. The primary efficacy variable was new-onset CDH at month 6. Secondary efficacy measures included migraine and headache days. Adverse events (AEs) were evaluated.

RESULTS

A total of 159 topiramate subjects and 171 placebo subjects were efficacy-evaluable. At month 6, 1.4% of topiramate subjects versus 2.3% of placebo subjects had CDH (p = .589). Compared with placebo, topiramate treatment was associated with statistically significant reductions in mean number of migraine days (6.6 vs. 5.3/28 days; p = .001) and headache days (6.6 vs 5.3/28 days; p = .001). Most commonly reported AEs in the topiramate versus placebo group included paresthesia (32.4% vs. 7.0%), fatigue (14.8% vs. 8.6%), dizziness (11.4% vs. 7.6%) and nausea (10.8% vs. 9.2%).

CONCLUSION

Topiramate 100 mg/day did not prevent the development of CDH at six months in subjects with HFEM. Topiramate was effective in reducing headache days and migraine headache days and generally well tolerated.

Psychiatric comorbidities and migraine chronification

A growing body of literature has implicated comorbid psychopathology as a potential risk factor for the chronification of migraine. Of the psychiatric disorders, depressive and anxiety disorders have been most consistently associated with the chronification of migraine. A shared dysfunction of the serotonergic system, medication overuse, and psychological factors have been proposed to mediate this relationship, although the responsible mechanisms are still largely unclear. This article overviews literature on psychiatric comorbidities and migraine chronification, considers mechanisms underlying this relationship, and notes directions for future clinical and empirical work.

Is Chronic Migraine One End of a Spectrum of Migraine or a Separate Entity?

Chronic migraine is associated with abnormalities in the periaqueductal grey that may be progressive. The condition is also associated with a greater degree of impairment in cortical processing of sensory stimuli than episodic migraine, perhaps due to more pervasive or persistent cortical hyperexcitability These findings fit with the model of migraine as a spectrum disorder, in which the clinical and pathophysiological features may progress over time. This progression may result from changes in nociceptive thresholds and ensuing central sensitization caused by recurrent migraine in susceptible individuals. This may lead to changes in baseline neurological function between headaches, evident not only in electrophysiological and functional imaging studies, but also as psychological and somatic complaints that occur after years of episodic migraine. From current research and migraine models, a conceptualization of chronic migraine is emerging in which relatively permanent and pervasive central changes have occurred that warrant novel and tolerable treatments.

Chronic headache and potentially modifiable risk factors: screening and behavioral management of sleep disorders

Sleep-related variables have been identified among risk factors for frequent and severe headache conditions. It has been postulated that migraine, chronic daily headache, and perhaps other forms of chronic headache are progressive disorders. Thus, sleep and other modifiable risk factors may be clinical targets for prevention of headache progression or chronification. The present paper is part of the special series of papers entitled "Chronification of Headache" describing the empirical evidence, future research directions, proposed mechanisms, and risk factors implicated in headache chronification as well as several papers addressing individual risk factors (ie, sleep disorders, medication overuse, psychiatric disorders, stress, obesity). Understanding the link between risk factors and headache may yield novel preventative and therapeutic approaches in the management of headache. The present paper in the special series reviews epidemiological research as a means of quantifying the relationship between chronic headache and sleep disorders (sleep-disordered breathing, insomnia, circadian rhythm disorders, parasomnias) discusses screening for early detection and treatment of more severe and prevalent sleep disorders, and discusses fundamental sleep regulation strategies aimed at headache prevention for at-risk individuals.

Headache chronification: screening and behavioral management of comorbid depressive and anxiety disorders

A growing body of literature implicates comorbid psychopathology as a risk factor for chronification of headache. Despite their prevalence, comorbid psychiatric conditions are not routinely assessed among headache patients. Consequently, efforts to manage such conditions are not commonplace either. The present article briefly reviews a variety of strategies and measures for psychiatric screening among headache patients, focusing primarily on those that have been validated in medical settings, that can be administered quickly, and that involve minimal associated costs. We also describe basic strategies for behavioral management of comorbid depression and anxiety in headache patients.