Headache physiology !
- Mechanism
- Exam priority: medium
The brain itself feels no pain; headaches come from the meninges, blood vessels, nerves and muscles around it.
Updated 2026-11-01
Also called: Cephalalgia, Trigeminovascular system
See it in 3D: Dura mater · Trigeminal nerve (V) · Middle meningeal artery · Superior sagittal sinus · Tentorium · Trigeminal ganglion
What it is
Brain tissue has no nociceptors. Headache arises when pain-sensitive structures are stretched, inflamed or irritated: the dura near the venous sinuses, the large arteries at the base of the brain, meningeal arteries, cranial and cervical nerves, and scalp and neck muscles. Where the pain is felt depends on which nerve carries it.
How it works, step by step
- A trigger (stretch, inflammation, traction or chemical irritation) activates nociceptors in the dura or in vessel walls.
- Supratentorial afferents travel in the trigeminal nerve (mostly its ophthalmic branch) to the trigeminal nucleus in the brainstem.
- Infratentorial afferents travel in the C2–C3 roots and converge on the same trigeminocervical complex.
- In migraine, activated trigeminal endings release CGRP, causing meningeal vasodilation and neurogenic inflammation that sensitizes the pathway.
- Central sensitization explains throbbing, sensitivity to light and sound, and pain with routine movement.
- A slow wave of neuronal depolarization spreading across the cortex (a few mm per minute) produces the visual aura that marches across the field.
Headache patterns and their physiology
| Type | Mechanism | Telltale feature |
|---|---|---|
| Migraine | Trigeminovascular activation, CGRP, central sensitization; aura from cortical spreading depression | Unilateral, throbbing, nausea, photophobia; worse with activity |
| Tension-type | Pericranial muscle tenderness and central pain-processing changes | Bilateral band-like pressure, no nausea |
| Subarachnoid hemorrhage | Blood irritates the meninges and raises intracranial pressure | Sudden worst-ever headache, neck stiffness |
| Raised intracranial pressure | Traction on dura and vessels | Worse lying down and in the morning, vomiting, papilledema |
| Post-lumbar puncture | CSF leak lowers pressure, brain sags | Worse standing, relieved lying flat |
Clinical notes
- Red flags for a secondary headache: sudden onset, fever with neck stiffness, a new headache after age 50, neurological deficits, papilledema, or pattern change.
- Giant cell arteritis causes new temporal headache in older adults with jaw claudication; it threatens vision.
- Medication-overuse headache: frequent analgesic use can itself maintain daily headache.
Test yourself
Think of the answer, then tap the question to see it.
Why can a neurosurgeon cut brain tissue in an awake patient without causing pain?
Brain parenchyma lacks nociceptors. Pain comes only from the dura, vessels, nerves and scalp, which are anesthetized locally.
A posterior fossa lesion causes pain at the back of the head. Why there and not in the forehead?
Structures below the tentorium are supplied by upper cervical nerves (C2–C3), whose skin territory is the occiput and neck; supratentorial pain uses the trigeminal nerve and is felt in front.
What explains the visual aura that slowly spreads across the visual field before a migraine?
Cortical spreading depression: a slow wave of neuronal depolarization followed by suppression, moving a few millimetres per minute across the occipital cortex.
Why does headache after a lumbar puncture get worse when the patient stands up?
Leaking CSF lowers its pressure; upright, the brain loses buoyancy and sags, pulling on pain-sensitive meninges and bridging veins. Lying flat removes the traction.
See it in 3D
The structures of Durgical's 3D anatomy where it happens.
- Dura mater
- Trigeminal nerve (V)
- Middle meningeal artery
- Superior sagittal sinus
- Tentorium
- Trigeminal ganglion
Related topics
- Pain and temperature: pathways and modulation
- Cerebral blood flow, brain metabolism and intracranial pressure
- CSF and the blood–brain barrier
Related conditions
In Pharmacology
Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.
Sources: 13.3 Circulation and the Central Nervous System (OpenStax (Rice University), 2022); Migraine Headache (StatPearls (NCBI Bookshelf), 2024); Muscle Contraction Tension Headache (StatPearls (NCBI Bookshelf), 2024); Subarachnoid Hemorrhage (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 49). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).
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Representative model, for educational purposes only.