Textbook Definition of Migraine
Migraine is defined by the International Classification of Headache Disorders (ICHD-3) as a recurrent headache disorder manifesting in attacks lasting 4-72 hours, characterized by at least two of the following: unilateral location, pulsating quality, moderate-to-severe pain intensity, or aggravation by routine physical activity, accompanied by either nausea/vomiting or both photophobia and phonophobia. 1
Core Diagnostic Criteria
The formal definition requires understanding three main subtypes:
Migraine Without Aura
This is the most common form and requires at least five attacks meeting all of the following 1:
Temporal criteria:
- Headache duration of 4-72 hours (untreated or unsuccessfully treated)
Pain characteristics (≥2 required):
- Unilateral location
- Pulsating quality
- Moderate or severe pain intensity
- Aggravation by or causing avoidance of routine physical activity (walking, climbing stairs)
Associated symptoms (≥1 required):
- Nausea and/or vomiting
- Photophobia AND phonophobia (both must be present together)
Exclusion:
- Not better accounted for by another ICHD-3 diagnosis
Migraine With Aura
Approximately one-third of migraine patients experience aura, defined as transient focal neurological symptoms that usually precede but sometimes accompany the headache 1. This requires at least two attacks with:
Aura symptoms (≥1 required):
- Visual (>90% of cases, classically fortification spectra)
- Sensory (31% of cases, typically unilateral paresthesia spreading gradually in face/arm)
- Speech and/or language
- Motor
- Brainstem
- Retinal
Temporal characteristics (≥3 of 6 required):
- At least one aura symptom spreads gradually over ≥5 minutes
- Two or more aura symptoms occur in succession
- Each individual aura symptom lasts 5-60 minutes
- At least one aura symptom is unilateral
- At least one aura symptom is positive (not just loss of function)
- Aura is accompanied by or followed by headache within 60 minutes
Critical distinction: Aura symptoms spread gradually over ≥5 minutes and occur in succession, whereas transient ischemic attack symptoms have sudden, simultaneous onset 1.
Chronic Migraine
Defined as ≥15 headache days per month for >3 months, with fulfillment of ICHD-3 criteria for migraine on ≥8 days per month 1. The patient must have had at least five previous attacks meeting criteria for migraine without aura and/or migraine with aura. On ≥8 days/month for >3 months, the headache must either meet criteria for migraine without aura, migraine with aura, or be believed by the patient to be migraine at onset and relieved by a triptan or ergot derivative.
Key Clinical Features
Prodromal symptoms (before pain onset):
- Depressed mood
- Yawning
- Fatigue
- Food cravings
Postdromal symptoms (after headache resolution, lasting up to 48 hours):
- Tiredness
- Concentration difficulties
- Neck stiffness
Important caveat: Bilateral pain occurs in approximately 40% of migraine patients, so unilateral location is not required for diagnosis 1.
Genetic Component
Migraine has a strong genetic component with higher prevalence among first-degree relatives, though family history may be under-reported by patients 1. Onset typically occurs at or around puberty 1.
Pathophysiology Context
While not part of the formal definition, migraine is understood as a neurovascular disorder involving cortical spreading depression (correlating with aura), brainstem and hypothalamic activation during the pain phase, and trigeminal nerve activation with CGRP release 2, 3. The disorder involves multiple neuronal systems functioning abnormally, creating a substrate for extreme sensitivity to homeostatic fluctuations 4.