When to Go to the ER for a Headache

What is a thunderclap headache and why is it an emergency?

A thunderclap headache is a severe headache that reaches peak intensity within 60 seconds — sometimes described as being struck on the back of the head. It is the hallmark warning sign of a subarachnoid hemorrhage (SAH), a bleed around the brain most often caused by a ruptured aneurysm. SAH is life-threatening and time-sensitive: the sooner treatment begins, the better the outcome.

The ACEP clinical policy for emergency evaluation of acute headache identifies the thunderclap pattern as a critical indicator for immediate imaging and workup, even when the patient looks and feels otherwise well 1Ref 1Wolf SJ, et al. (ACEP Clinical Policies Subcommittee on Acute Headache) (2019).Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Acute Headache.Emergency evaluation for thunderclap headache; criteria warranting CT and lumbar puncture workup for subarachnoid hemorrhage.

Which headache warning signs mean call 911 right now?

Go to the ER or call 911 immediately for any of these:

• Thunderclap onset — worst headache of your life, maximum pain within 60 seconds
• Headache plus stroke signs — face drooping, arm weakness, slurred speech, sudden vision changes (use BE-FAST: Balance, Eyes, Face, Arm, Speech, Time to call) 2Ref 2Aroor S, Singh R, Goldstein LB (2017).BE-FAST (Balance, Eyes, Face, Arm, Speech, Time): Reducing the Proportion of Strokes Missed Using the FAST Mnemonic.BE-FAST mnemonic for recognizing stroke symptoms alongside headache
• Headache plus stiff neck and fever — suggests meningitis, which can be fatal within hours
• Headache plus confusion, loss of consciousness, or seizure
• Headache after a head injury, especially if you blacked out or the pain is worsening
• New severe headache in someone over 50 who has never had headaches before — can indicate giant cell arteritis or an intracranial lesion
• Headache with one-sided face or body numbness, double vision, or loss of coordination
• Headache that wakes you from sleep and progressively worsens over days or weeks — can indicate elevated pressure inside the skull

What happens in the ER for a headache like this?

Emergency evaluation for a dangerous headache typically includes:

• CT scan of the brain without contrast — can detect blood from a ruptured aneurysm within hours of onset 1Ref 1Wolf SJ, et al. (ACEP Clinical Policies Subcommittee on Acute Headache) (2019).Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Acute Headache.Emergency evaluation for thunderclap headache; criteria warranting CT and lumbar puncture workup for subarachnoid hemorrhage
• Lumbar puncture (spinal tap) — if CT is negative but SAH is still suspected, spinal fluid is checked for blood products (xanthochromia or red cells)
• Blood tests — to look for infection, clotting problems, or metabolic causes
• MRI or CT angiography — if a vascular malformation or stroke is suspected

Emergency clinicians do not send someone home after a thunderclap headache without a full workup, even if initial scans look normal.

What about headaches that are severe but not sudden?

Not every severe headache is an emergency. Migraines can be extremely painful and disabling without representing a threat to life. A headache that follows your usual pattern — same location, same triggers, same relieving factors — is much less likely to be dangerous than a completely new type.

If you have a bad headache that is not the worst of your life and has none of the red flags above, and you can safely get there, urgent care or a same-day clinician visit (rather than the ER) is often appropriate. A Gale clinician can help you assess whether your headache pattern warrants urgent evaluation or can be managed with a telehealth or in-person visit.

Among adults, head pain is the fifth leading cause of emergency department visits overall 3Ref 3Smitherman TA, Burch R, Sheikh H, Loder E (2013).The prevalence, impact, and treatment of migraine and severe headaches in the United States: a review of statistics from national surveillance studies.Head pain is the fifth leading cause of emergency department visits overall; migraine prevalence 11.7% plus 4.5% probable migraine in US adults.