Headache brings more people to their GP and A&E than almost any other neurological symptom. The anxiety that accompanies it is understandable - the brain is involved, and we know that some headaches represent serious pathology. Brain tumours, bleeds, meningitis. The fear is not irrational.
But here is the reality that is worth stating clearly: the vast majority of headaches - well over 90% - are primary headaches. Tension type, migraine, or cluster. They are real, sometimes debilitating, but not dangerous in themselves. They will not cause brain damage and they will not kill you. The minority that do require urgent investigation have recognisable features - specific red flags that are worth knowing and responding to without hesitation.
The thunderclap headache - always an emergency
A thunderclap headache is defined as a severe headache that reaches its maximum intensity within 60 seconds of onset. It is often described as the worst headache of my life or like being hit on the head.
This presentation is a neurological emergency until proven otherwise. The primary concern is subarachnoid haemorrhage (SAH) - bleeding into the space around the brain from a ruptured cerebral aneurysm. SAH is fatal in approximately 40% of cases and causes significant disability in many survivors. But if caught quickly, the aneurysm can be treated before a second, often fatal, bleed occurs.
Do not wait to see if the pain settles. Do not take paracetamol and go to bed. Call 999.
A CT scan of the head is the first investigation. If normal, a lumbar puncture is performed to look for blood in the cerebrospinal fluid - the CT can miss early SAH in a small proportion of cases.
Other causes of thunderclap headache include cerebral venous sinus thrombosis, hypertensive emergency, reversible cerebral vasoconstriction syndrome, and pituitary apoplexy - all requiring urgent assessment.
Tension headache - the most common type
Tension-type headaches affect approximately 80% of adults at some point. They are characterised by a dull, aching, bilateral (both sides) pain - often described as a band or vice gripping the head. The pain builds gradually, is typically moderate in intensity, and lasts 30 minutes to several hours. There is no nausea or vomiting, and activity does not worsen it significantly.
Triggers include stress, poor posture (particularly prolonged screen use), dehydration, disrupted sleep, jaw clenching, and eyestrain. They are not dangerous and do not indicate brain disease.
Treatment: Simple analgesia - paracetamol 1g or ibuprofen 400mg at the first sign of a headache - is effective when taken promptly. Physiotherapy for neck and shoulder tension is helpful for recurrent tension headaches. If you are taking pain relief more than 10-15 days per month for headaches, read the medication overuse section below.
Prevention: Low-dose amitriptyline (10-25mg at night) taken daily reduces the frequency of chronic tension headache. It is not an antidepressant at these doses - it is used specifically for headache prevention.
Migraine - a neurological disorder, not just a bad headache
Migraine affects approximately 1 in 7 people and is the second most disabling neurological condition in the world. It is significantly more common in women than men. It is still dramatically undertreated, partly because it is often dismissed as a bad headache rather than recognised as the complex neurological disorder it is.
Classic migraine features: moderate to severe, typically unilateral (one side, though it can be bilateral), throbbing or pulsating pain lasting 4-72 hours without treatment. Associated with nausea or vomiting, and photophobia (sensitivity to light) or phonophobia (sensitivity to sound) that makes normal daily activity impossible. The diagnostic criterion is that the headache significantly impairs functioning - this is not a headache you can push through.
Migraine with aura: Approximately 30% of migraines are preceded by an aura - a neurological symptom lasting 20-60 minutes that develops gradually and then resolves completely before or as the headache begins. Visual aura is most common: zigzag lines, shimmering arcs (scintillating scotoma), blind spots, or flashing lights. Aura can also include unilateral tingling or numbness, speech difficulty, or rarely motor weakness. Aura symptoms are caused by cortical spreading depression - a wave of neuronal depolarisation and suppression spreading across the brain.
It is important to know that migraine with aura slightly increases the risk of ischaemic stroke, particularly in women who smoke and use the combined oral contraceptive pill. If you have migraine with aura and are on the pill, this combination needs discussion with your GP.
Acute migraine treatment: Triptans are the most effective acute treatment for migraine. They work by constricting the dilated cranial blood vessels and blocking pain signal transmission. Sumatriptan 50-100mg oral, or 6mg subcutaneous injection (fastest onset), or 20mg nasal spray. Rizatriptan 10mg oral wafers dissolve on the tongue without water - useful during an attack. Take as early as possible in the migraine attack. Do not use in people with cardiovascular disease.
NSAIDs (ibuprofen 400-600mg, naproxen 500mg) combined with an antiemetic (prochlorperazine, metoclopramide) are effective for mild-moderate migraine. Take at the very first sign of attack.
Paracetamol alone is often inadequate for migraine.
Migraine prevention: If you have more than 4 migraine days per month, preventive treatment significantly improves quality of life. Options include: topiramate (effective but has cognitive side effects at higher doses and is teratogenic - absolutely avoid in pregnancy or if pregnancy possible without reliable contraception); propranolol (a beta-blocker, well-tolerated, effective); amitriptyline; and the newer CGRP antagonists (erenumab/Aimovig, fremanezumab/Ajovy) which are highly effective with excellent tolerability and are available on NHS prescription for people who have failed two prior preventives.
Medication overuse headache (MOH): If you are taking any pain relief - including triptans - on more than 10-15 days per month for headache, you may have medication overuse headache. Paradoxically, the medication is now maintaining and worsening the headache cycle. The only treatment is withdrawal of the overused medication under GP supervision. This typically causes a temporary worsening before improvement. Discuss with your GP.
Cluster headache - the most severe primary headache
Cluster headaches are less common (affecting approximately 1 in 1,000) but are often described as the most severe pain in human experience. They cause excruciating, unilateral periorbital (around one eye) pain rated 10/10 by virtually everyone who has them. The ipsilateral eye is typically red, watering, and the eyelid may droop. The nostril on the same side runs or blocks. Unlike migraine sufferers who lie still, people with cluster headaches are agitated and restless.
They occur in clusters lasting weeks to months, typically at the same time of day (often waking people at 1-3am), then remit completely for months to years.
Acute treatment: subcutaneous sumatriptan 6mg (fastest effective treatment) or high-flow 100% oxygen (12-15 L/min for 15 minutes) via non-rebreather mask. Both are available on NHS prescription. Standard oral pain relief is largely ineffective due to the rapid onset and resolution of attacks.
Prevention during a cluster period: verapamil (a calcium channel blocker) is most effective. Refer to neurology for management.
Headache in African and Black patients - specific considerations
Uncontrolled hypertension is a more common cause of headache in Black patients given the higher rates of hypertension. Occipital headache (back of the head) that is worse in the morning and associated with a high blood pressure reading warrants blood pressure investigation and control.
Vitamin D deficiency - near-universal in dark-skinned UK residents - is associated with headache in some individuals. Worth checking and treating.
Sources: NICE Clinical Guideline CG150 - Headaches in over 12s (2012, updated 2021); British Association for the Study of Headache (BASH) guidelines 2019; Steiner TJ et al, Journal of Headache and Pain 2018; NHS - Headaches overview; Headache UK - Cluster Headache patient information; Dodick DW, NEJM 2018 (CGRP antagonists for migraine).
