Refractory migraine and chronic migraine: pathophysiological mechanisms

Predictors of galcanezumab response in a real-world study of Korean patients with migraine

To assess factors associated with galcanezumab response in a real-world study of Korean patients with migraine. Predictors of the efficacy of monoclonal antibodies targeting calcitonin gene-related peptide (CGRP) or its receptor (anti-CGRP(-R) mAb) have been rarely investigated in Asians. We prospectively recruited and followed up patients with migraine who received monthly galcanezumab treatment in a single university hospital from June 2020 to October 2021. We defined the treatment response with ≥ 50% reduction in moderate/severe headache days in the 3rd month of treatment compared to baseline. Responders and non-responders were compared in terms of demographics, disease characteristics and severity, and previous response to migraine prophylactic treatments. Potential predictors of anti-CGRP(-R) mAb response were tested by using the univariable and multivariable logistic regression analyses. Among 104 patients (81.7% female; mean age 42.0 ± 13.02; 76.9% chronic migraine; and 45.5% medication overuse headache) included, 58 (55.7%) were responders. Non-responders had more chronic migraine, medication overuse headache, monthly headache days, days with acute medication, and daily headaches (i.e. chronic migraine persisting everyday without remission). The multivariable logistic analysis showed chronic migraine (OR 0.05 [95% CI 0.00-0.82], p = 0.036) and the number of previously failed preventive medication classes (OR 0.55 [95% CI 0.33-0.92], p = 0.024] were independently associated with treatment response. Chronic migraine and multiple failures from preventive medication are associated with poor galcanezumab response. Further studies are needed to investigate if earlier treatment before disease chronification or multiple failures may lead to a greater therapeutic gain from anti-CGRP(-R) mAb treatment.

The evolving classifications and epidemiological challenges surrounding chronic migraine and medication overuse headache: a review

Changes in diagnostic criteria, for example, the various International Classification of Headache Disorders criteria, would lead to changes in the outcomes of epidemiological studies. International Classification of Headache Disorders-1 was based mainly on expert opinion, yet most of the diagnostic criteria were reliable and valid, but it did not include chronic migraine. In its second version, the classification introduced chronic migraine, but this diagnosis resembled more a high-frequency migraine rather than the actual migraine transformation process. It also introduced medication overuse headache, but it necessitated analgesic withdrawal and subsequent headache improvement to be diagnosed as such. Hence patients having medication overuse headache could only be diagnosed in retrospect, which was an awkward situation. Such restrictive criteria for chronic migraine and medication overuse headache omitted a high proportion of patients. International Classification of Headache Disorders-3 allows a diagnosis of medication overuse headache due to combination analgesics if taken for at least 10 days per month for more than three months. Hence the prevalence rate of medication overuse headache and chronic migraine can increase compared to the previous version of the headache classification. Different criteria have been used across studies to identify chronic migraine and medication overuse headache, and therefore the information acquired from previous studies using earlier criteria becomes uncertain. Hence much epidemiological research would need to be interpreted cautiously or repeated with the most updated criteria, since the subjects in studies that apply the latest criteria may be phenotypically different from those in older studies.

Beyond the Raskin Protocol: Ketamine, Lidocaine, and Other Therapies for Refractory Chronic Migraine

PURPOSE OF REVIEW

The purpose of this review is to discuss the available evidence and therapeutic considerations for intravenous drug therapy for refractory chronic migraine.

RECENT FINDINGS

In carefully monitored settings, the inpatient administration of intravenous lidocaine and ketamine can be successful in treating refractory chronic migraine. Many patients with refractory chronic migraine have experienced treatment failure with the Raskin protocol. The use of aggressive inpatient infusion therapy consisting of intravenous lidocaine or ketamine, along with other adjunctive medications, has become increasingly common for these patients when all other treatments have failed. There is a clear need for prospective studies in this population comprised of patients who have largely been excluded from other studies.

Dysregulation of the peripheral glutamatergic system: A key player in migraine pathogenesis?

Background

Although the role of glutamate in migraine pathogenesis remains uncertain, there has been significant interest in the development of drug candidates that target glutamate receptors. Activation of trigeminovascular afferent fibers is now recognized as a crucial step to the onset of a migraine episode. New evidence suggests a dysfunction in peripheral glutamate regulation may play a role in this process.

Objective

To provide a narrative review of the role of peripheral glutamate dysfunction in migraine.

Method

A review of recent literature from neurobiological, pharmacological and genomic studies was conducted to support peripheral glutamate dysfunction as a potential element in migraine pathogenesis.

Results

Studies in rats suggest that elevated blood glutamate mechanically sensitizes trigeminal afferent fibers and stimulates the release of calcitonin-gene related peptide and other neuropeptides to promote and maintain neurogenic inflammation. These effects may be driven by upregulation of glutamate receptors, and modifications to reuptake and metabolic pathways of glutamate. Furthermore, genome wide association studies have found polymorphisms in glutamate receptor and transporter genes that are associated with migraine.

Conclusion

The role of peripheral glutamate signalling in the onset and maintenance of migraine is not completely elucidated and future studies are still needed to confirm its role in migraine pathogenesis.

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.

Animal Models of Chronic Migraine

PURPOSE OF REVIEW

Chronic migraine (CM) is a recalcitrant subtype of migraine which causes high degrees of disability, poor treatment responses, and frequent recurrences in sufferers. However, the pathophysiological mechanisms underlying the development and chronification of migraine attacks remain incompletely understood. A validated animal model could help to decipher the pathogenic mechanism of the disease, facilitating the development of possible therapeutic strategies for CM. In this review, we aimed to summarize current animal models of CM and discuss the validity of these models.

RECENT FINDINGS

Several methods have been available to induce recurrent headache-like behaviors or biochemical changes in rodents, including repeated dural application of inflammatory soup, chronic systemic infusion of nitroglycerin, repeated administration of acute migraine abortive treatment to simulate medication overuse headache, or genetic modification. These models exhibit some features that are believed to be associated with migraine; however, none of the model can recapitulate all the clinical phenotypes found in humans and each has its own weakness. The complex features of CM increase the difficulty of constructing a proper animal model. Nonetheless, currently available models are valid to certain degrees. Future directions might consider simulating the spontaneity and chronicity of migraine by combining known genetic substrates and allostatic loads into the same model.

Chronic migraine: Classification and comparisons

Objective: The objective of our study was to field test different chronic migraine (CM) criteria and compare CM epidemiological profiles, which include demographic, personal, and lifestyle characteristics, with high-frequency episodic migraine (HFEM) and low-frequency episodic migraine (LFEM).

Methods: Questionnaires were mailed to a random sample of 18,000 18–65-year-olds in demographically diverse regions of Germany. The epidemiological data for the three classifications of CM, LFEM and HFEM were assessed using descriptive statistics, Pearson Chi-square, and analysis of variance tests.

Results: Among 9350 respondents, CM_I was the most restrictive ( N = 37, 0.4%), followed by CM_II ( N = 45, 0.5%) and CM_III ( N = 185, 2.0%). CM groups did not differ in distribution by age, gender, body mass index, education or smoking and alcohol consumption. Compared to those with LFEM and HFEM, those with CM (CM_III) had significantly different epidemiological profiles.

Conclusions: CM prevalence varies by case definition. The epidemiological profiles of the three CM groups are similar but differ significantly from those of HFEM and LFEM. Optimal definitions for clinical practice and epidemiological research require additional field testing.

Chronic pain disorders and headache chronification

It is estimated that nearly half of the global adult population suffers from an active headache disorder, most of whom experience attacks on an episodic basis. The transition from episodic to chronic headache is a poorly understood process. Epidemiological findings demonstrating comorbidity and common risk factors suggest that headache progression or prognosis may be related to the presence of other chronic pain disorders. This review highlights findings from population-based studies on headache and other pain disorders and how they relate to each other, with a focus on understanding headache chronification. We also consider the limitations and methodological challenges in understanding how two different chronic pain disorders may be related.