Migraine and Neuroinflammation: How Inflammation Drives the Attack Cycle

Inflammation is not a concept commonly associated with migraine in popular understanding. The condition is most often framed in terms of pain, triggers, and vascular effects. But neuroinflammation, inflammation within the nervous system and its surrounding structures, is now recognized as a central mechanism in migraine pathophysiology. Understanding how inflammation contributes to migraine attacks, why it develops, what it produces, and how it can be interrupted provides a more complete picture of the condition than pain-focused models alone.

Neuroinflammation in migraine is distinct from the systemic inflammation associated with infections or autoimmune conditions. It is localized, primarily involving the meningeal tissues surrounding the brain, and it is driven by the activation of trigeminal nerve fibers rather than by immune system dysfunction. The inflammatory process that develops during a migraine attack is both a consequence of trigeminovascular activation and a contributor to the pain and sensitization that characterize the attack.

Neurogenic Inflammation in the Meninges

When the trigeminal nerve fibers that innervate the meningeal blood vessels are activated during a migraine attack, they release inflammatory neuropeptides including calcitonin gene-related peptide, substance P, and neurokinin A. These neuropeptides produce a cascade of inflammatory changes in the meningeal tissues surrounding their release sites.

Calcitonin gene-related peptide causes vasodilation of the meningeal blood vessels and increases their permeability, allowing plasma proteins to leak into the surrounding tissue. Substance P activates mast cells in the dura, causing them to release additional inflammatory mediators including histamine, serotonin, and prostaglandins. These inflammatory mediators further sensitize the trigeminal nerve endings surrounding the meningeal vessels, lowering their threshold for activation and amplifying the pain signal.

This process of neurogenic inflammation in the meninges is distinct from the inflammatory processes that occur in peripheral tissues during injury or infection. It does not involve immune cell infiltration or systemic markers of inflammation. It is a local, neuronally driven inflammatory response that both results from and perpetuates trigeminal activation during a migraine attack.

Central Neuroinflammation and Sensitization

Beyond the peripheral meningeal inflammation driven by trigeminal neuropeptide release, there is evidence that neuroinflammation extends to the central nervous system in migraine. Microglia, the resident immune cells of the brain, are activated in animal models of migraine and release pro-inflammatory cytokines that can sensitize central pain pathways.

Central neuroinflammation may contribute to the phenomenon of central sensitization, in which the pain-processing neurons of the brainstem and thalamus become sensitized during an attack, lowering their threshold for activation and producing the widespread pain hypersensitivity characteristic of severe migraine attacks. Allodynia, the perception of non-painful stimuli as painful during migraine attacks, is a clinical manifestation of central sensitization that reflects the contribution of neuroinflammation to the attack state.

The role of neuroinflammation in the transition from episodic to chronic migraine is an active area of research. Repeated episodes of neuroinflammation may contribute to the sensitization of pain pathways that characterizes chronic migraine, in which the nervous system remains in a state of heightened reactivity even between attacks.

Anti-inflammatory Mechanisms of Migraine Treatments

Several effective migraine treatments work in part through anti-inflammatory mechanisms. Nonsteroidal anti-inflammatory drugs, including ibuprofen and naproxen, inhibit cyclooxygenase enzymes that produce prostaglandins, reducing the inflammatory contribution to meningeal sensitization. Their effectiveness as acute migraine treatments reflects the role of prostaglandin-mediated inflammation in migraine pain.

Triptans, the most widely prescribed migraine-specific acute medications, inhibit the release of CGRP and other inflammatory neuropeptides from trigeminal nerve terminals, directly reducing neurogenic inflammation in the meninges. CGRP monoclonal antibodies prevent CGRP from binding to its receptor, blocking the vasodilatory and pro-inflammatory effects of CGRP in the meningeal tissues.

Corticosteroids, sometimes used to treat refractory migraine attacks or status migrainosus, work through broad anti-inflammatory mechanisms that reduce meningeal inflammation and may help break prolonged attack cycles.

Mast Cells and Dural Inflammation

Dural mast cells are increasingly recognized as important players in migraine-related neuroinflammation. Mast cells are resident immune cells in the dura that contain large quantities of inflammatory mediators including histamine, serotonin, and prostaglandins. When activated by substance P released from trigeminal nerve endings, mast cells degranulate, releasing their contents into the surrounding tissue.

The inflammatory mediators released by mast cell degranulation sensitize trigeminal nerve fibers, amplify the neurogenic inflammatory response, and may lower the threshold for subsequent attacks. The clustering of mast cells near meningeal blood vessels innervated by the trigeminal nerve positions them as amplifiers of the neuroinflammatory process during migraine attacks.

Dietary histamine, released by mast cells in the gut following ingestion of histamine-containing foods, may also influence dural mast cell activity through systemic mechanisms, providing one explanation for the observation that histamine-rich foods can trigger migraine attacks in susceptible individuals.