How Migraines Work: Triggers, Phases, Neurological Mechanisms, and Treatment

This article is for informational purposes only. Consult a qualified healthcare professional for medical advice, diagnosis, or treatment.

What Is a Migraine?

A migraine is a complex neurological disorder characterized by recurrent episodes of moderate-to-severe headache, typically unilateral and pulsating, that last between 4 and 72 hours. It is the third most prevalent illness in the world, affecting roughly 1 billion people, and consistently ranks among the top causes of years lived with disability globally. Despite its prevalence, migraine remains significantly underdiagnosed and undertreated. Women are three times more likely than men to experience migraines, a disparity linked to hormonal fluctuations.

Neurological Mechanism: What Actually Happens in the Brain

For decades migraines were dismissed as a vascular phenomenon caused by dilation of cerebral blood vessels. Modern neuroimaging has revealed a far more nuanced picture involving several interacting brain systems.

Cortical Spreading Depression (CSD): The migraine aura—when it occurs—is produced by a wave of intense neuronal firing followed by prolonged suppression that sweeps across the cortex at approximately 3–5 mm per minute. This phenomenon, called cortical spreading depression, explains the characteristic visual disturbances (flickering lights, zigzag fortification spectra) that march across the visual field over 20–30 minutes.

Trigeminal Activation: CSD and other initiating events activate the trigeminal nerve, the primary sensory nerve of the head and face. Trigeminal fibers release neuropeptides—most importantly calcitonin gene-related peptide (CGRP)—that cause neurogenic inflammation in the meningeal blood vessels, producing the throbbing pain characteristic of migraine.

Central Sensitization: During prolonged attacks, central pain-processing pathways become sensitized, which explains allodynia (pain from normally non-painful stimuli, such as light touch on the scalp) and why head movement worsens the pain.

The Four Phases of Migraine

Common Triggers

Triggers do not cause migraines directly; rather, they lower the threshold for an attack in susceptible individuals. The brain of a migraineur is fundamentally more excitable and less able to habituate to sensory stimuli. Common triggers include:

• Hormonal changes: Estrogen withdrawal before menstruation is the most potent trigger for many women; oral contraceptives can worsen migraine with aura.
• Sleep disruption: Both sleep deprivation and excessive sleep are strongly linked to attacks.
• Dietary factors: Skipping meals, dehydration, alcohol (especially red wine), caffeine withdrawal, and—in susceptible individuals—tyramine-rich foods like aged cheese.
• Sensory stimuli: Bright or flickering lights, loud sounds, strong odors.
• Psychological stress and its aftermath: The "let-down" migraine after stress resolves is well documented.
• Weather and barometric pressure changes: Frequently reported but difficult to control.
• Medications: Overuse of acute headache medications (opioids, triptans, NSAIDs) can paradoxically cause chronic migraine—medication overuse headache (MOH).

Diagnosis

Migraine is diagnosed clinically using the International Classification of Headache Disorders (ICHD-3) criteria. There is no definitive biomarker or imaging test for primary migraine. Red flag features—sudden thunderclap onset, fever, neurological deficits, papilledema, or age over 50 at first onset—warrant urgent neuroimaging to rule out secondary causes such as subarachnoid hemorrhage, meningitis, or intracranial mass.

Acute and Preventive Treatments

Chronic Migraine and Disability

When headache occurs on 15 or more days per month for at least three months (with migraine features on at least 8 days), the condition is classified as chronic migraine. This affects roughly 1–2% of the general population and is associated with significant occupational, social, and psychological impairment. Medication overuse headache—a common complication—must be addressed by gradually withdrawing the offending analgesic, a process that initially worsens headache before improving it.

Living with Migraines

Effective migraine management involves a partnership between patient and clinician. Keeping a headache diary to track frequency, severity, duration, and potential triggers helps guide treatment decisions. Emerging wearable neuromodulation devices (transcranial magnetic stimulation, external trigeminal nerve stimulators) offer non-pharmacological options with favorable safety profiles. With optimal treatment, most patients can significantly reduce attack frequency and improve quality of life.