Headache and Migraine

Headache disorders are among the most common nervous-system conditions, and migraine is one of the leading causes of disability worldwide. This topic covers how headaches are classified into primary disorders such as migraine and tension-type headache and secondary headaches attributable to another cause, with particular attention to migraine as a recurrent, often disabling headache syndrome.

Definition

Headache disorders are conditions in which headache is the principal feature; they are divided into primary headaches (such as migraine, tension-type headache, and cluster headache), in which the headache is the disorder itself, and secondary headaches caused by an underlying condition, following the International Classification of Headache Disorders.

Scope

The entry summarises the classification of headache disorders, the clinical features and phases of migraine, the mechanisms thought to underlie migraine attacks, and the concept of chronic migraine and medication-overuse headache. It is a reference overview and does not provide diagnostic protocols or treatment recommendations.

Key concepts

• Primary vs secondary headache
• Migraine with and without aura
• Tension-type headache and cluster headache
• Trigeminovascular system
• Calcitonin gene-related peptide (CGRP)
• Chronic migraine and medication-overuse headache

Mechanisms

Migraine is understood as a disorder of the brain involving the trigeminovascular system. Activation and sensitisation of trigeminal sensory pathways that innervate cranial blood vessels and the meninges, together with release of neuropeptides such as calcitonin gene-related peptide (CGRP), are central to the headache phase. Cortical spreading depression — a slowly propagating wave of neuronal and glial depolarisation — is the substrate thought to underlie the aura. Migraine attacks unfold through phases (premonitory, aura, headache, and postdrome), and the role of CGRP has become a focus of mechanistic understanding of the condition.

Clinical relevance

Because migraine is highly prevalent and a major cause of years lived with disability, recognising headache patterns and distinguishing primary from secondary headaches is important across clinical settings. This entry describes headache disorders and migraine mechanisms as reference material; it is not a basis for individual diagnosis or treatment, and warning features that may indicate secondary headache are assessed clinically.

Epidemiology

Headache disorders affect a large share of the adult population, and migraine in particular is one of the leading global causes of disability, with a marked female predominance during the reproductive years, as summarised in current reviews of migraine.

History

Headache has been described since antiquity, but systematic classification advanced substantially with the International Headache Society's International Classification of Headache Disorders, first published in 1988 and revised through its third edition. The identification of the trigeminovascular system and of calcitonin gene-related peptide as key elements of migraine biology reshaped the modern understanding of the disorder.

Debates

Is migraine primarily a vascular or a neuronal disorder?

Earlier vascular theories of migraine have given way to a view of migraine as a primarily neuronal disorder of brain excitability and the trigeminovascular system, though the relative contributions of neural and vascular components continue to be discussed.

Key figures

• Messoud Ashina
• Jes Olesen
• Peter Goadsby

Seminal works

• ichd3-2018
• ashina-2020

Frequently asked questions

What is the difference between primary and secondary headache?

A primary headache, such as migraine or tension-type headache, is the disorder itself, whereas a secondary headache is a symptom caused by an underlying condition such as infection, trauma, or a vascular problem.

What is chronic migraine?

Chronic migraine is defined in the headache classification as headache occurring on 15 or more days per month for more than three months, with features of migraine on at least eight of those days.