Most headaches are not dangerous. But a small set of "red flag" features should be treated as a medical emergency: thunderclap onset, fever with stiff neck, sudden severe headache after age 50, new neurological deficits that do not resolve, headache after head injury, or the worst headache of your life. If any of these are present, do not call your primary care provider. Go directly to the emergency room or call emergency services. Time-sensitive conditions including subarachnoid hemorrhage, stroke, meningitis, and brain abscess present this way.
Headache emergencies are rare but real. Headache specialists use a memory aid called SNNOOP10 to screen for them. Here is the patient version, organized so you can act on it.
The 7 absolute emergencies
If any of these are present, call emergency services or go to the nearest emergency room. Do not drive yourself.
1. Thunderclap headache
A headache that reaches maximum intensity in under 60 seconds, often described as "like being hit with a baseball bat." This is the classic presentation of subarachnoid hemorrhage from a ruptured aneurysm. Mortality without treatment is roughly 50%. Survival depends on imaging within hours.
2. Headache with fever and stiff neck
Especially if you cannot touch your chin to your chest. This is the classic triad for bacterial meningitis. Bacterial meningitis can kill in 24 hours and demands IV antibiotics within the first hour of presentation.
3. New neurological deficits
Weakness, numbness, slurred speech, vision loss, or facial droop that does not resolve within an hour. This can be a stroke. The "FAST" rule (Face, Arms, Speech, Time) applies. Tissue plasminogen activator (tPA) must be given within 3 to 4.5 hours of symptom onset to be effective.
People with hemiplegic migraine can have stroke-like symptoms that are not strokes. But the only safe assumption when symptoms are new is stroke until proven otherwise.
4. Headache after head injury
Especially if it worsens over hours, or comes with confusion, vomiting, or loss of consciousness. Subdural and epidural hematomas can present hours to days after impact.
5. The worst headache of your life
If you have a long migraine history and this attack is qualitatively different and more severe than anything you have had, take it seriously. Do not assume it is "just a bad migraine."
6. Sudden new headache after age 50
New-onset headache after 50, especially with scalp tenderness, jaw pain when chewing, or vision changes, can be giant cell arteritis. Untreated, this causes permanent vision loss. Diagnosis requires same-day blood work (ESR, CRP) and high-dose steroids before biopsy.
7. Headache with cancer history, HIV, or immunosuppression
In these populations, new headaches require imaging to rule out metastases, abscess, or opportunistic infection. The threshold for ER evaluation is lower.
The 6 "urgent but not 911" red flags
These warrant a same-day or next-day call to your neurologist, urgent care, or telehealth:
- New aura after 50, especially without prior migraine history
- Aura that lasts more than an hour per symptom
- Aura on the same side every single attack (so-called "always-right" or "always-left" pattern can suggest a structural lesion)
- Headache that wakes you from sleep consistently, or is worst on first waking
- Headache worsened by coughing, sneezing, or straining, which can indicate raised intracranial pressure
- Progressive headache that has gotten steadily worse over weeks
These are not necessarily emergencies, but they require evaluation rather than self-management.
Red flags during pregnancy and postpartum
Pregnant or postpartum patients have a uniquely elevated risk profile. A new severe headache in the third trimester or first 6 weeks postpartum may signal preeclampsia, cerebral venous sinus thrombosis, or reversible cerebral vasoconstriction syndrome. Blood pressure check and same-day evaluation are warranted. See pregnancy and headaches.
When your "usual" migraine looks unusual
Your migraine is a known pattern. Any new feature deserves attention:
- New location (always-left becomes right)
- New character (throbbing becomes stabbing)
- New trigger that has never bothered you before
- Steady increase in frequency over a few weeks
- Loss of medication response that used to work
These are not necessarily dangerous, but they warrant a neurology visit, not a wait-and-see.
What to bring to the ER
If you do go to the emergency room, bring:
- A list of your usual migraine medications and last doses
- Your tracking history (peak severity, frequency, prior treatments)
- Allergies and other medications, especially blood thinners
- A trusted person to advocate for you, because severe pain makes you a poor reporter
The bottom line: trust your gut. If something feels qualitatively different, get evaluated. The worst case of a needless ER visit is reassurance. The worst case of ignoring a red flag is permanent.
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