What Is Migraine?

Migraine is a chronic neurological disorder characterized by recurrent attacks of moderate to severe head pain, typically pulsating and one-sided, lasting from four to seventy-two hours and accompanied by nausea, vomiting, or heightened sensitivity to light and sound. It is classified as a primary headache disorder, meaning the headache is the condition itself rather than a symptom of separate structural disease. Diagnosis rests on symptom criteria published by the International Headache Society rather than on imaging or a laboratory marker, and imaging is used chiefly to exclude other causes. The World Health Organization counts headache disorders among the most common conditions of the nervous system, with migraine concentrated in the working years between puberty and midlife and roughly twice as prevalent in women as in men.

Attacks proceed through recognizable phases. A premonitory phase of yawning, food craving, mood change, or neck stiffness may precede pain by hours. About a third of patients experience aura, a reversible neurological disturbance that is usually visual, presenting as a slowly expanding scintillating arc, and less often sensory or aphasic. The headache phase follows, and a postdrome of fatigue and difficulty concentrating can persist for a further day.

Pathophysiology

Migraine is now understood as a disorder of brain excitability rather than a primary vascular event. Aura is attributed to cortical spreading depression, a slow wave of neuronal and glial depolarization that advances across the cortex at roughly three millimeters per minute and is followed by suppressed electrical activity. During the wave, extracellular potassium and glutamate rise by more than an order of magnitude while intracellular sodium and calcium increase, and the propagation speed matches the march of visual aura symptoms across the visual field. Reviews of cortical spreading depression and migraine and of the molecular and cellular neurobiology of spreading depolarization describe how the wave activates the trigeminovascular system, sensitizes meningeal afferents, and drives release of calcitonin gene-related peptide, the neuropeptide that has become the principal drug target in the field. Familial hemiplegic migraine, caused by mutations in ion channel and pump genes including CACNA1A, ATP1A2, and SCN1A, provides direct genetic evidence that altered ionic homeostasis lowers the threshold for these events.

Measurement and Monitoring

Because attacks are episodic and diagnosis is symptom based, quantitative characterization has depended on patient diaries, which are subject to recall error. Instrumented approaches have grown accordingly. Electroencephalography and magnetoencephalography measure cortical responses that habituate abnormally between attacks, functional and structural magnetic resonance imaging track brainstem and hypothalamic activation in the premonitory phase, and wearable sensors recording heart rate variability, skin conductance, actigraphy, and ambient light are used to test whether attacks can be forecast from physiological precursors. Direct intracranial recording during spontaneous aura is rare, so much of the mechanistic evidence comes from animal models and from monitoring in patients with traumatic brain injury or subarachnoid hemorrhage, where similar depolarization waves occur.

Device-Based Treatment

Pharmacological management combines acute agents, including triptans, gepants, and ditans, with preventive therapy such as beta blockers, topiramate, onabotulinumtoxinA, and monoclonal antibodies against calcitonin gene-related peptide or its receptor. Alongside these, several noninvasive neuromodulation devices have received regulatory clearance: single-pulse transcranial magnetic stimulation applied to the occiput, supraorbital transcutaneous stimulation of the trigeminal nerve, noninvasive vagus nerve stimulation at the neck, and remote electrical neuromodulation delivered through an armband that engages descending pain inhibition. Evidence summaries on neuromodulation in chronic migraine assess these devices against pharmacological alternatives, particularly for patients who cannot tolerate drug therapy.

Applications

Migraine research has applications in a range of fields, including:

• Neuromodulation device design and clinical validation
• Wearable sensing and attack forecasting algorithms
• Neuroimaging methods for episodic brain disorders
• Computational modeling of cortical spreading depolarization
• Drug discovery targeting neuropeptide signaling and ion channels
• Occupational health and disability burden assessment