Thunderclap headaches live up to their name, striking suddenly like a clap of thunder. The pain of these severe headaches peaks within 60 seconds.

Thunderclap headaches are uncommon, but they can warn of potentially life-threatening conditions — usually having to do with bleeding in and around the brain. Seek emergency medical attention for a thunderclap headache.

Thunderclap headaches are dramatic. Symptoms include pain that:

• Strikes suddenly and severely
• Peaks within 60 seconds
• Can be accompanied by nausea or vomiting

Thunderclap headaches might be accompanied by other signs and symptoms, such as:

• Altered mental state
• Fever
• Seizures

These signs and symptoms might reflect the underlying cause.

When to see a doctor

Seek immediate medical attention for any headache that comes on suddenly and severely.

There's no obvious cause for some thunderclap headaches. In other cases, a variety of potentially life-threatening conditions might be responsible, including:

• Bleeding between the brain and membranes covering the brain (subarachnoid hemorrhage)
• A rupture of a blood vessel in the brain
• A tear in the lining of an artery that supplies blood to the brain
• Leaking of cerebrospinal fluid — usually due to a tear of the covering around a nerve root in the spine
• Death of tissue or bleeding in the pituitary gland
• A blood clot in the brain
• Severe elevation in blood pressure (hypertensive crisis)
• Infection such as meningitis or encephalitis
• Ischemic stroke

The following tests are commonly used to try to determine the cause of a thunderclap headache.

• CT scan of the head. CT scans take X-rays that create slice-like, cross-sectional images of your brain and head. A computer combines these images to create a full picture of your brain. Sometimes an iodine-based dye is used to augment the picture.
• Spinal tap (lumbar puncture). The doctor removes a small amount of the fluid that surrounds your brain and spinal cord. The cerebrospinal fluid sample can be tested for signs of bleeding or infection.
• MRI. In some cases, this imaging study might be done for further assessment. A magnetic field and radio waves are used to create cross-sectional images of the structures within your brain.
• Magnetic resonance angiography. MRI machines can be used to map the blood flow inside your brain in a test called a magnetic resonance angiography (MRA).

Treatment is aimed at the cause of the headaches — if one can be found.

Thunderclap headaches are often diagnosed in an emergency room. However, if you call to set up an appointment with your own doctor, you might be referred immediately to a doctor who specializes in the brain and nervous system (neurologist).

If you have time to prepare for your appointment, here's some information to help you get ready.

What you can do

Make a list of:

• Your symptoms, including any that may seem unrelated to your headaches, and when they began
• Key personal information, including major stresses, recent life changes and medical history
• All medications, vitamins and other supplements you take, including doses
• Questions to ask your doctor

Take a family member or friend along, if possible, to help you remember the information you receive.

Some questions to ask your doctor include:

• What is likely causing my headaches?
• Are there other possible causes for my headaches?
• What tests do I need?
• Is my condition likely temporary or chronic?
• What is the best course of action?
• I have these other health conditions. How can I best manage them together?
• Are there restrictions I need to follow?
• Should I see a specialist?
• Are there brochures or other printed material I can take with me? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you questions, including:

• Have you had other thunderclap headaches?
• Do you have a history of other headaches?
• If you've had other headaches, have they been continuous or occasional?
• Describe your headaches and their symptoms
• How severe are your headaches?
• What, if anything, seems to improve your headaches?
• What, if anything, appears to worsen your headaches?