A migraine attack triggers a chain of electrical, chemical, and vascular changes that ripple across brain regions over hours or days. Cortical spreading depression, trigeminal nerve activation, and calcitonin gene-related peptide release converge to produce throbbing pain, sensory sensitivity, nausea, and lingering brain fog. The World Health Organization classifies migraine among the most disabling medical conditions worldwide, ranking it alongside active psychosis and dementia in years lost to disability.
You will find a phase-by-phase breakdown of the four stages of an attack and the brain mechanisms behind each one. It is written for anyone who has wondered whether their migraine is doing lasting damage, or struggled to explain an invisible neurological event to a coworker.
Migraine Is a Neurological Event, Not Just a Bad Headache
Migraine ranks second on the global list of years lived with disability, yet it remains widely mischaracterized as a stubborn headache. The distinction matters because a tension-type headache arises from muscle tension and stress, producing a tight, band-like ache on both sides of the head, while a cluster headache delivers brief, searing pain around one eye in cyclical bouts.
A migraine, by contrast, originates deep inside the brain itself, involving abnormal signaling between neurons, blood vessels, and pain-processing centers.
Three neurological features separate migraine from other primary headaches:
- Unilateral throbbing pain, often worsened by movement and lasting 4 to 72 hours if untreated.
- Sensory amplification, where ordinary light, sound, or smells become unbearable during an attack.
- Associated symptoms, including nausea, vomiting, and cognitive slowing that can disable daily functioning even after the headache fades.
The four-phase model gives a useful map of what happens in your brain during a migraine. The prodrome arrives hours or even a day before the headache, with yawning, food cravings, or mood changes. The aura phase, when present, brings visual zigzags or tingling sensations as a wave of altered electrical activity moves across the cortex. The headache phase is when trigeminal pain circuits and CGRP-driven inflammation peak.
The postdrome, sometimes called a migraine hangover, leaves fatigue and brain fog as the excitatory-inhibitory balance slowly resets.
That cascade leaves a clear neural fingerprint, beginning with the wave of depolarization that marks the aura phase.
The Electrical Storm: Cortical Spreading Depression and the Aura Phase
Cortical spreading depression is a slow wave of depolarization that sweeps across the brain’s surface at roughly 3 millimeters per minute, silencing neurons as it passes. First described in animal studies and later confirmed in humans using functional imaging, this wave is the leading explanation for migraine aura.
What Aura Actually Looks Like in the Brain
The wave often begins in the occipital lobe at the back of the head, which is why visual disturbances are the most common aura symptom. You might see shimmering arcs, blind spots, or zigzag lines expanding outward across your visual field. When the wave crosses the sensory cortex, it produces tingling or numbness, typically starting in one hand and marching up the arm. When it reaches language areas, words briefly become hard to find.
Tip: Noticing the speed and direction of an aura can help you recognize the earliest stage of an attack and move to a quiet, dark room before the headache peaks.
Aura can also occur without a subsequent headache, a pattern called silent migraine. The fact that the electrical wave appears independently of pain suggests that aura and headache are triggered by related but separable mechanisms, both rooted in the same hyperexcitable brain.
How the Electrical Wave Connects to Pain
As cortical spreading depression passes through pain-processing regions, it activates the trigeminal nerve fibers that wrap around the meninges. This downstream activation is the bridge from electrical disturbance to the throbbing pain that follows. The aura phase lights the fuse, and the trigeminovascular system carries the spark into the headache phase.
The Chemistry of Pain: Neurotransmitters, CGRP, and the Trigeminal Pathway
The headache phase is driven by a chemical storm centered on the trigeminovascular system. Once cortical spreading depression or other triggers activate trigeminal nerve endings around the meninges, those nerves release inflammatory molecules that dilate blood vessels and sensitize nearby pain fibers.
Serotonin and CGRP: The Two Key Molecules
Serotonin, also called 5-HT, is a neurotransmitter that helps regulate mood, sleep, and pain. During a migraine, serotonin levels fluctuate, causing cranial blood vessels to dilate and lowering the brain’s overall pain threshold. CGRP, or calcitonin gene-related peptide, is a signaling molecule that rises sharply during attacks, promoting vasodilation, meningeal inflammation, and pain signal amplification.
The trigeminovascular pathway is the wiring that connects these molecules to your conscious experience of pain. The pathway runs from the meninges to the brainstem, relays through the thalamus, and finally reaches the sensory cortex where pain is perceived. A signal that begins as irritation in the membranes around the brain becomes a full-blown, central pain event.
Why the Pain Often Localizes to One Side
A single branch of the trigeminal nerve usually fires on one side during an attack, which is why migraine pain so often stays localized. Bilateral migraine does occur, but the one-sided pattern remains a key diagnostic clue that the trigeminal nerve, rather than generalized muscle tension, is at the center of the attack.
Once the trigeminal pathway is firing, the brain’s sensory thresholds collapse, which is why ordinary light and sound cut so deep.
Why Light, Sound, and Smell Feel Agonizing During an Attack
During a migraine, stimuli that the brain normally filters out become loud, bright, or overwhelming. This is not a problem with your eyes or ears; it is a problem with how the brain processes sensory input.
The Thalamus Goes Into Overdrive
The thalamus acts as the brain’s relay station for sensory information. During a migraine, thalamic neurons become hyperresponsive, amplifying signals from light, sound, and touch far beyond their normal level. Photophobia and phonophobia are the direct consequences of this sensitized circuitry. Even gentle conversation or ordinary room lighting can feel like an assault.
Brainstem nuclei are caught in the same cascade. The nucleus tractus solitarius, a brainstem center that regulates nausea, becomes activated alongside pain pathways. That is why nausea and vomiting often arrive with the headache rather than after it.
Mood, Fog, and the Distributed Migraine Network
Cognitive symptoms are equally neurological. Word-finding difficulty, slowed thinking, and mood shifts reflect the fact that migraine affects distributed brain networks, not just isolated pain centers. Functional imaging studies show altered activity in the prefrontal cortex, basal ganglia, and cerebellum during attacks. The brain fog many people experience is a measurable change in how those regions communicate.
How Migraine Medications Intervene in the Brain’s Pain Circuitry
Treatments for migraine work because they interrupt specific steps in the neurological cascade described above. Understanding where each type of intervention acts can help you have more productive conversations with your neurologist.
Acute Abortives vs. Preventive Agents
Acute abortives, taken at the onset of an attack, are designed to halt the cascade once it has begun. Triptans act as serotonin receptor agonists, constricting dilated cranial blood vessels and blocking pain transmission in the trigeminal nucleus. NSAIDs work upstream by reducing prostaglandin-driven inflammation around the meninges.
Preventive agents aim to lower the brain’s baseline excitability so attacks are less frequent or less severe. Beta-blockers, certain antidepressants, and CGRP-targeting therapies all belong to this category, but they act at different points. CGRP monoclonal antibodies and gepants bind or block the CGRP molecule itself, preventing it from triggering vasodilation and pain signal amplification. Beta-blockers and antidepressants modulate neuronal excitability more broadly, reducing the brainstem and thalamic hyperresponsiveness that underlies the migraine tendency.
| Treatment Class | When Used | Where It Acts |
|---|---|---|
| Triptans | At onset of attack | Serotonin receptors on cranial vessels and trigeminal nucleus |
| NSAIDs | At onset of attack | Meningeal inflammation, prostaglandin pathways |
| CGRP antibodies / gepants | Prevention or acute | CGRP molecule and its receptor |
| Beta-blockers and certain antidepressants | Daily prevention | Brainstem and thalamic excitability |
Note: Your neurologist can help match the right preventive strategy to your attack pattern, frequency, and symptom profile.
The shared goal across all of these approaches is to lower the brain’s sensitivity to migraine triggers and shorten or prevent the cascade once it begins.
Lowering that sensitivity takes time, and repeated attacks reshape the brain in ways that make each one worth interrupting early.
Brain Recovery, Long-Term Effects, and Why Migraine Is Worth Taking Seriously
The postdrome is its own neurological phase, not just exhaustion after pain. During this stage, the brain is recalibrating its excitatory-inhibitory balance after hours of heightened activity. Fatigue, mood changes, and residual cognitive fog reflect that recalibration.
What Frequent Attacks May Mean for Brain Structure
Some studies using MRI have found small white matter lesions in people who experience migraine with aura or who have very frequent attacks. The clinical significance of these lesions is still debated, and they are not the same as the damage seen in stroke or dementia. What is clear is that uncontrolled, frequent migraine is a signal worth taking seriously, both for quality of life and for long-term brain health.
Warning Signs That Call for Urgent Evaluation
Some symptoms fall outside the typical migraine pattern and warrant immediate medical attention. Reach out to a healthcare professional right away if you experience any of the following:
- Sudden worst-ever headache, sometimes called a thunderclap headache, reaching peak intensity in seconds.
- New neurological deficits, such as weakness on one side, slurred speech, or vision loss that does not match a familiar aura.
- Fever, stiff neck, or confusion alongside the headache, which can indicate infection or other serious conditions.
- Headache after head injury, or a new headache pattern after age 50.
Understanding the brain mechanisms behind your attacks changes the kind of conversations you can have with a specialist. When you can describe prodrome, aura, sensory sensitivity, and postdrome in the language of cortical spreading depression and CGRP, your neurologist has more to work with. Informed self-knowledge is the foundation for better treatment choices.
Bottom Line
A migraine is a full-brain event, not a local pain problem. Electrical waves, neurotransmitter shifts, and inflammatory molecules move through cortical, brainstem, and vascular circuits in a predictable four-phase sequence. Knowing how those phases unfold puts you in a stronger position to recognize early warning signs, choose strategies that fit your pattern, and partner with your neurologist on prevention.
FAQ
What part of the brain is affected during a migraine?
Migraine affects multiple brain regions, including the cortex (where aura originates), the brainstem (where pain and nausea signals are amplified), the thalamus (where sensory input becomes overwhelming), and the trigeminal nerve endings around the meninges.
Why does a migraine cause nausea and light sensitivity?
Nausea arises because brainstem nuclei that control vomiting become activated during the migraine cascade. Light sensitivity arises because the thalamus and sensory cortex become hyperresponsive, amplifying normal visual input into pain.
How long does a migraine attack last in the brain?
A typical untreated attack lasts between 4 and 72 hours. The full neurological sequence, including prodrome and postdrome, can extend over several days.
Can migraines cause permanent brain damage?
Brain scans of people with frequent or aura-laden migraines sometimes reveal tiny white matter spots, but these rarely translate into lasting harm. These changes are not the same as stroke-related damage, and their long-term significance is still being studied.
What is cortical spreading depression in migraines?
A sluggish ripple of electrical change sweeps across the cortex at roughly 3 millimeters per minute, lighting up neurons and triggering the visual zigzags or tingling that herald an aura.
How do migraine medications work on the brain?
Acute medications like triptans constrict dilated cranial vessels and block pain signals in the trigeminal nucleus. Preventive therapies, including CGRP inhibitors, reduce the brain’s baseline excitability so attacks start less easily.
