A brain aneurysm is a weak, bulging spot on the wall of a blood vessel in the brain. If this weakened spot ruptures, it releases blood into the space surrounding the brain, causing a subarachnoid hemorrhage (SAH). This is a life-threatening medical emergency. The first and most common symptom of a ruptured aneurysm is a sudden, extremely severe headache. The duration of the pain varies significantly depending on whether the aneurysm has fully burst or is simply leaking.
Recognizing the Thunderclap Headache
The hallmark of a ruptured brain aneurysm is a specific type of pain known as a thunderclap headache. This term describes the speed at which the pain reaches its maximum intensity, which is a key feature distinguishing it from other types of head pain. The headache progresses from normalcy to excruciating pain in less than 60 seconds, often peaking within 30 seconds of onset.
Patients frequently describe a thunderclap headache as the “worst headache of their life.” The pain is typically diffuse, affecting the entire head, and is often accompanied by nausea and vomiting. This instant onset of extreme pain results from blood suddenly flooding the space around the brain, causing immediate irritation and pressure. The severity and speed of this pain signal the underlying subarachnoid hemorrhage.
How Long the Peak Pain Persists
While the pain of a thunderclap headache reaches its peak intensity instantly, the severe pain does not immediately resolve. The initial peak is reached within seconds, but the debilitating pain associated with the hemorrhage persists for a much longer period. The headache lasts for a minimum of five minutes, but the severe pain often remains intense for several hours or even days.
The lingering pain is caused by the continued presence of blood and its breakdown products irritating the meninges, the membranes covering the brain and spinal cord. Symptoms like a stiff neck and sensitivity to light often develop as the blood irritates these membranes. Without medical intervention, the headache will continue until the underlying issue is addressed.
Headaches from Aneurysms That Have Not Ruptured
Not all headaches related to a brain aneurysm indicate a full rupture. An unruptured aneurysm may cause pain if it is large enough to press on nearby nerves or brain tissue, sometimes called a mass-effect headache. These headaches are often chronic and localized to one area. They can be accompanied by symptoms like pain above or behind one eye, double vision, or a drooping eyelid.
Another specific type of pain is the “sentinel headache,” which occurs when a small amount of blood leaks from the aneurysm before a major rupture. This warning leak causes a sudden, intense headache that is worse than a typical headache but less severe than a full thunderclap event. Sentinel headaches can precede a major rupture by days or even weeks. Up to 60% of people who experience an aneurysmal rupture report having a sentinel headache beforehand.
When to Seek Emergency Medical Care
Any headache that is sudden and severe, described as the “worst ever,” demands immediate emergency medical evaluation, regardless of how long it lasts after the initial onset. The defining characteristic is the speed and intensity of the pain, not its duration. A ruptured aneurysm is a time-sensitive medical emergency where delays in treatment can have serious consequences.
The need for emergency care is amplified if the sudden, severe headache is accompanied by other neurological symptoms. These associated signs include a stiff neck, sudden nausea or vomiting, confusion, sensitivity to light, or any change in consciousness. Other concerning symptoms are sudden visual changes, weakness, or numbness on one side of the face or body. Recognizing these combined symptoms and calling emergency services immediately is the most important action.