What Happens in the Brain During a Migraine?

For a long time, migraine was thought to be a vascular condition. The throbbing pain, the way it pulsated with each heartbeat, pointed toward blood vessels as the culprit. Treatments were designed around that assumption. Some of them worked, but the explanation was incomplete.

Research over the past three decades has fundamentally changed how the medical community understands migraine. It is now recognized as a complex neurological event that involves the brain, the nervous system, and a cascade of biological processes that begin long before the headache arrives and continue after it ends. Understanding what actually happens during an attack does not make migraine easier to live with, but it does make it harder to dismiss.

The Brain Before the Attack

Migraine does not begin with pain. For many people, the first signs appear hours or even a full day before the headache phase. This is called the prodrome, and it reflects genuine neurological activity.

During the prodrome, people may experience mood changes, food cravings, increased yawning, neck stiffness, or heightened sensitivity to light and sound. These symptoms are not imagined and they are not unrelated to what follows. They reflect activity in the hypothalamus, a region of the brain that plays a central role in regulating sleep, appetite, and the body's internal clock. Research using neuroimaging has shown increased hypothalamic activation in the hours before a migraine attack begins, supporting the idea that this region may serve as a kind of pacemaker for the disorder.

Cortical Spreading Depression

In attacks that involve aura, a wave of electrical activity moves across the surface of the brain. This phenomenon is called cortical spreading depression, and it was first described in 1944 by the Brazilian physiologist Aristides Leao. It has since become one of the most studied mechanisms in headache research.

The wave begins in the occipital cortex, the region at the back of the brain responsible for processing visual information. It moves slowly forward, leaving a trail of suppressed neuronal activity in its wake. This is what produces the visual disturbances associated with migraine aura. The classic zigzag lines, the expanding arc of shimmering light, the blind spot that drifts across the visual field, all of these are the perceptual signature of cortical spreading depression moving across the visual cortex.

As the wave passes, it triggers the release of inflammatory substances and activates the trigeminal nerve, which becomes the primary pain pathway of the migraine attack.

The Trigeminal System and Pain

The trigeminal nerve is the largest cranial nerve. It carries sensation from the face, scalp, and the meninges, the protective membranes surrounding the brain, to the brainstem. During a migraine attack, this nerve becomes activated and inflamed. It releases a neuropeptide called calcitonin gene-related peptide (CGRP), which causes blood vessels to dilate and further amplifies the pain signal.

CGRP has become one of the most important targets in migraine research and treatment. Studies published in journals including Neurology and Cephalalgia have consistently shown that CGRP levels rise significantly during migraine attacks and return to baseline when the attack resolves. The development of CGRP antagonists and anti-CGRP monoclonal antibodies, now among the most effective treatments available for migraine prevention, is a direct result of this line of research.

The pain of a migraine attack is not simply the result of dilated blood vessels pressing on surrounding tissue. It is the product of a sensitized nervous system, inflamed meningeal blood vessels, and a pain signaling pathway that has become amplified in ways that make ordinary sensations feel unbearable.

Central Sensitization

One of the most clinically significant findings in migraine neuroscience is the phenomenon of central sensitization. As an attack progresses, the pain processing centers of the brain become increasingly sensitive. Signals that would not normally be painful begin to register as painful. This is why, during a migraine, even light touch on the scalp can hurt. This symptom, called allodynia, is reported by a substantial portion of migraine sufferers and is a marker of central sensitization.

Central sensitization also helps explain why treating migraine early in an attack is more effective than waiting. Once sensitization sets in, the pain becomes harder to interrupt. The window for effective acute treatment narrows as the attack progresses.

The Postdrome

The headache eventually ends, but the attack does not. The postdrome, sometimes called the migraine hangover, follows the pain phase and can persist for up to twenty-four hours. People in the postdrome commonly report fatigue, cognitive difficulties, mood changes, and a general sense of feeling depleted. Neuroimaging studies have shown continued changes in brain activity during this phase, confirming that what people describe is a real neurological state and not simply recovery from exertion.

What This Means for Treatment

Understanding migraine as a neurological disorder rather than a bad headache changes how it should be approached. It explains why standard pain relievers often provide inadequate relief. It explains why migraine-specific medications that target the trigeminal system and CGRP pathways tend to work better. It explains why prevention matters, because a brain that is repeatedly exposed to the migraine cascade becomes more sensitive over time, not less.

It also explains why tracking attacks is valuable. The triggers that initiate the cascade, the patterns that precede it, and the treatments that interrupt it most effectively are all individual. A migraine diary does not just document suffering. It maps the neurology of a person's specific condition in ways that inform better treatment decisions.