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.

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