Abstract
Chronic migraine is a highly disabling disease with a great impact on socioeconomic functioning and quality of life of migraine patients. Chronic migraine usually evolves from episodic migraine that gradually increases in attack frequency, supporting the view of migraine as a spectrum disorder. Pathophysiological mechanisms responsible for migraine chronification are not fully understood. Likewise episodic migraine, chronic migraine patients show widespread functional and structural alterations of cortical and subcortical pain-related brain areas. However, chronic migraine patients experience a more pronounced dysfunction of the pain inhibitory network and an increased sensitization of the central pain pathways, which might explain the higher susceptibility to migraine attacks. Imaging studies have highlighted that brain regions with a key role in migraine attack generation, like the pons and hypothalamus, might also be involved in migraine chronification. Whether brain alterations are biomarkers that predispose migraine patients to chronification or reflect adaptive or maladaptive responses to the increasing headache frequency is still a matter of debate. The central mechanisms of action of chronic migraine preventive treatments and imaging biomarkers that could predict patients' treatment response have also been explored. In this new era of migraine treatments, a better understanding of chronic migraine pathophysiology will pave the way for the development of new improved treatments specifically designed for chronic migraine patients.
Highlights
Chronic migraine is a highly disabling disease
At least 50% of patients with chronic migraine regularly overuse one Neuroimaging in Chronic Migraine or more drugs usually taken for acute migraine treatment, fulfilling the diagnosis of chronic migraine with medication overuse [2, 7, 8]
Significant advances in our understanding of chronic migraine pathophysiology have been made over the last years
Summary
Chronic migraine is a highly disabling disease. Relative to episodic migraine, patients with chronic migraine have greater headache-related impact on socioeconomic functioning and worse quality of life [1]. Chronic migraine usually evolves from episodic migraine that gradually increases in attack frequency, with an annual progression rate of about 3% [3, 4]. There is evidence that an altered balance between the facilitatory and inhibitory activity of pain-related brain regions might contribute to the development of symptoms commonly reported by chronic migraine patients, like cutaneous allodynia [12, 13]. Our understanding of the pathophysiology of chronic migraine has improved considerably with a series of imaging studies, which have provided insights into the function and structure of human brain networks that could be involved in migraine chronification. This review will focus the attention on neuroimaging studies in patients with chronic migraine, highlighting the evidence behind the involvement of key brain areas, such as the pons and hypothalamus, and the pain network in migraine chronification.
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