Thunderclap Headache

A Sudden, Explosive Headache, Like a Clap of Thunder

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Thunderclap Headache Is a Medical Emergency

If you are experiencing a thunderclap headache, call 911 immediately.

A thunderclap headache strikes suddenly, causing severe, explosive head pain that rapidly peaks in intensity within one minute and lasts at least five minutes. While not common, thunderclap headaches are warning signs of potentially fatal conditions, like bleeding within or around the brain.

This article will review the symptoms, causes, diagnosis, and treatment of a thunderclap headache. It will also explain why a thunderclap headache is a medical emergency that's almost always considered dangerous.

Bald person with beard in hospital scrubs experiencing a headache

The Good Brigade / Getty Images

Symptoms of Thunderclap Headache

Individuals with a thunderclap headache often describe it as the worst headache they have ever experienced. The headache is excruciatingly painful and begins abruptly and unexpectedly, like a clap of thunder.

A thunderclap headache may exist alone or be accompanied by other symptoms, depending on its cause.

Such symptoms may include:

  • Neck stiffness and light sensitivity
  • Loss of consciousness
  • Confusion or changes in speech or thinking
  • Seizure
  • Nausea
  • Weakness or numbness of a body part
  • Fever
  • Worsening headache when standing up
  • Cranial nerve palsies (malfunction of nerves in the head), like impaired eye movements with third cranial nerve palsy

Causes of Thunderclap Headache

Thunderclap headache is classified as either a primary or secondary headache.

Primary Thunderclap Headache

Primary thunderclap headaches do not have an underlying medical cause and are believed to be benign (harmless) and not dangerous. This rare primary headache disorder may occur on its own or be triggered by cough, exercise, or sexual activity.

Diagnosis of Exclusion

Diagnosis of a primary thunderclap is one of exclusion. This means an exhaustive approach to rule out secondary causes must be performed first.

Secondary Thunderclap Headache

An underlying health factor within the brain causes secondary thunderclap headaches, such as a blood vessel problem, an unusual structural abnormality, trauma, or an infection.

The most common secondary cause of a thunderclap headache is subarachnoid hemorrhage. Subarachnoid hemorrhage is a dangerous, potentially life-threatening brain bleed in which blood pools in the space between the brain and the tissue layer covering it.

Subarachnoid hemorrhage is usually caused by head trauma or a ruptured brain aneurysm (a bulging blood vessel in the brain that bursts open).

Another common cause of a thunderclap headache is reversible cerebral vasoconstriction syndrome (RCVS). With RCVS, the blood vessels in the brain suddenly tighten, and a person experiences multiple thunderclap headaches over a few days to weeks.

Thunderclap headaches caused by RCVS are often triggered by exercise, sex, emotional stress, the Valsalva maneuver (bearing down while holding your breath), or bathing.

Less common but still serious causes of a thunderclap headache include:

Uncommon or rare secondary causes of a thunderclap headache include:

  • Acute sinusitis (particularly with barotrauma) is nasal passage inflammation associated with rapid changes in air pressure.
  • A colloid cyst of the third ventricle is a benign growth in the third ventricle (narrow cavity in the brain's center).
  • Pituitary apoplexy is when a tumor (growth) within the pituitary gland (located deep within your brain) bleeds or outgrows its blood supply.
  • A brain tumor is a collection of abnormal cells that grows uncontrollably in the brain (very rare cause).

How to Treat a Thunderclap Headache

The treatment of a thunderclap headache depends on whether it's a primary or secondary headache.

Primary Thunderclap Headache

A primary thunderclap headache is treated with a nonsteroidal anti-inflammatory drug (NSAID), commonly Indocin (indomethacin).

Secondary Thunderclap Headache

The treatment of a secondary thunderclap headache involves addressing the underlying cause.

For example, individuals with subarachnoid hemorrhage are treated in a hospital's intensive care unit (ICU).

In the ICU, medications are given to control blood pressure and seizure activity. Blood-thinning medicines like aspirin and Jantoven (warfarin) are also discontinued to help stop bleeding.

A surgical procedure prevents rebleeding if a ruptured aneurysm causes a subarachnoid hemorrhage.

Surgery for Ruptured Aneurysm

One of the following surgeries is performed for a ruptured aneurysm:

  • Surgical clipping: A neurosurgeon (a doctor who performs surgery on the brain and spinal cord) removes a part of the skull and places a small clip on the neck of the aneurysm to stop its blood supply.
  • Endovascular coiling: An interventional neuroradiologist (a doctor who uses imaging/catheter-based techniques) places a catheter into the groin artery, threading it through the body to the brain. Small thin metal coils are passed through the catheter and released into the aneurysm to stop blood flow.

Examples of treatments for other conditions include:

  • Reversible cerebral vasoconstriction syndrome: Treatment is supportive, focusing on managing blood pressure and the pain of the headache. Avoiding potential triggers (e.g., exercise, sexual activities) is also advised.
  • Ischemic stroke: Treatment with tissue plasminogen activator, or tPA, when given within three hours of symptom onset, can help reopen clogged arteries.
  • Meningitis: Medications directed against the pathogen (bug) causing the infection (e.g., antibiotics, antivirals) are given through an IV (needle in your vein).

Complications Associated With a Thunderclap Headache

Various complications may arise depending on the underlying cause of a thunderclap headache.

For instance, people with a subarachnoid hemorrhage typically stay in the intensive care unit (ICU) for several days or weeks to stabilize and be monitored for complications.

Possible complications of a subarachnoid hemorrhage include:

Examples of possible complications for other conditions include:

  • Reversible cerebral vasoconstriction syndrome: Most people have a favorable outcome, although stroke leading to death occurs in up to 2% of cases. Also, more than 50% of individuals with RCVS develop mild or moderate chronic headaches. Long-term anxiety and depression are also common.
  • Stroke: Depending on the location and severity of the stroke, various brain-related problems may occur, such as problems speaking, moving, thinking, or swallowing. Depression after a stroke is also common.

Are There Tests to Diagnose the Cause of a Thunderclap Headache?

Diagnosing the cause of a thunderclap headache requires prompt medical action.

The first test is almost always a computed tomography (CT) scan of the brain to check for subarachnoid hemorrhage, the most common and catastrophic cause.

What Is a CT Scan?

A CT scan is an imaging test that uses X-rays and a computer to create pictures of the inside of the body.

If the CT scan is negative for bleeding around the brain, a lumbar puncture (spinal tap) is performed. Excess red blood cells in the cerebrospinal fluid support a diagnosis of subarachnoid hemorrhage.

Other diagnostic tests used to investigate a thunderclap headache include:

  • Magnetic resonance imaging (MRI) of the brain (uses magnetic fields and radio waves to create three-dimensional images of the body's soft tissues)
  • Computed tomography angiography (CTA) of the brain (a CT of the brain's blood vessels)
  • Magnetic resonance angiography (MRA) of the brain (an MRI of the brain's blood vessels)
  • Magnetic resonance venography (MRV) of the brain (an MRI of the brain's veins)

When to See a Healthcare Provider

A thunderclap headache always warrants emergency medical investigation. Call 911 if your headache is severe, begins suddenly, and/or feels like the "worst headache of your life."


A thunderclap headache is a sudden, explosive headache that reaches its maximum pain intensity within one minute. Most thunderclap headaches are secondary headaches with an attributable cause, like bleeding or a blood vessel problem within the brain.

CT scans, a spinal tap, and other imaging tests are used to diagnose the underlying cause of most thunderclap headaches. Treatment involves addressing the root cause, often including intensive care, intravenous medications, or surgery.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Colleen Doherty, MD
 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.