Most common cause of episodic headache

Aetiology

• More common in females - 1:2.5
• Triggers: sleep, diet, stress, hormonal, physical exertion

Pathophysiology

Migraine without aura (80%)

• Both vascular and neural influences cause migraines in susceptible individuals
• Stress triggers changes in the brain which cause serotonin to be released
• Blood vessels constrict and dilate
• Chemicals including substance P irritate nerves and blood vessels causing pain

Migraine with aura (20%)

1. Cortical spreading depolarisation in the migraine centre of the brain (dorsal raphe nucleus, locus coeruleus)
2. Activation of the trigeminal vascular system causes dilation of blood vessels
3. Release of substance P, neurokinin A, CGRP

→ Increased sensitivity

• In both cases, the chemicals result in the sensitisation of trigeminal neurones and brainstem pain pathways
• This makes otherwise innocuous sensory stimuli (such as CSF pulsation and head movement) painful, and light and sound are perceived as uncomfortable

Clinical features

• Classically, a unilateral throbbing headache preceded by an aura, such as visual (eg. lines, zigzags) or sensory (paraesthesia spreading from fingers to face) symptoms
• The headache may last 4-72 hours and is associated with photophobia and phonophobia