Thunderclap Headache

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.

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.

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:

• A hemorrhagic stroke is bleeding from a blood vessel that bursts into the brain tissue.
• An ischemic stroke is when a blocked artery interrupts blood flow to the brain.
• Cervical artery dissection is a tear in the inner wall of one or more of the large arteries in the neck.
• Cerebral venous sinus thrombosis occurs when a blood clot forms within a large vein in the brain.
  
• Spontaneous intracranial hypotension is low pressure within the skull due to reduced cerebrospinal fluid (a clear fluid that cushions the brain and spinal cord).
• Meningitis is inflammation of the membranes surrounding the brain and spinal cord.

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.

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:

• Rebleeding
• Vasospasm (when arteries in the brain rapidly spasm and narrow, possibly leading to stroke)
• Elevated intracranial pressure (increased pressure in the skull)
• Low sodium levels (hyponatremia)

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.

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."

Summary

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.