Thunderclap headaches come on quickly without warning and are extremely painful—and they can be a sign of something serious. Learn how to spot a thunderclap headache and what to do if you experience one.
A thunderclap headache feels like a sudden, severe headache that comes on within less than a minute. This extremely abrupt onset and head pain unlike any you’ve experienced before can be a terrifying experience, and most often requires urgent medical attention. Although many times no cause is found, the first occurrence of a thunderclap headache can be a sign of something very serious.
What Is a Thunderclap Headache?
Thunderclap headaches are severe headaches coming on full force in less than a minute, lasting at least 5 minutes, and often appearing without any trigger. The pain may be felt anywhere in the head and may in some cases extend down the back of the neck.
In some cases, a thunderclap headache may be accompanied by fever, weakness, confusion, loss of vision or sensation, or changes in speech or thinking. If you experience any of these symptoms alongside a thunderclap headache, you should seek immediate medical attention.
What Causes a Thunderclap Headache?
Thunderclap headaches can be divided broadly into two groups:
- Those caused by vascular or blood vessel problems, injury, or uncommon structural problems in the brain
- Those that have no clear cause and, following medical evaluation, are felt to be benign (not dangerous)
Abrupt, severe headaches triggered by activity—including sexual activity or straining to have a bowel movement—or headaches coming on after an injury have especially high potential to be dangerous.
There is a broad range of possible injuries and underlying conditions that can result in thunderclap headaches, and the consequences can be severe. Below we cover many of the potential causes of a thunderclap headache.
Blood Vessel Tear (Dissection), Rupture, or Blockage
A decrease in blood flow to the brain can cause a severe headache, and is often accompanied by weakness, numbness, or changes in vision or sensation. Sudden decreases in blood flow can come from blood vessels narrowing (spasming), rupturing, a stroke, a head injury, or a structural weakening of blood vessel walls, as can occur with an aneurysm. It is not clear when a thunderclap headache occurs whether it is due to one of these potentially dangerous causes, and for this reason, urgent medical evaluation is recommended.
Dissection (a tear in the wall of a blood vessel) and aneurysm (a weakening in the wall of a blood vessel) can both cause sudden, painful headaches. Dissection can be triggered by an injury, including a fall or neck whiplash. Dissection or aneurysm bleeding can come on after exertion, such as lifting weights. Both conditions can also occur in individuals who have an inherited weakness in their blood vessels that increases the likelihood of such a dissection or aneurysm. However, sometimes a dissection or aneurysm can occur for no known reason.
Stroke Caused by Bleeding
The rupture of a blood vessel in the brain can result in a hemorrhagic stroke. These strokes are more likely to occur in people with uncontrolled high blood pressure. However, an otherwise healthy weight lifter can develop a sudden headache that does not go away after they stop activity, coming from a brain bleed called a subarachnoid hemorrhage related to rupture of an aneurysm, or from the tear in the blood vessels of the neck resulting in a dissection. A person who develops a severe headache with sexual activity or orgasm can also have a bleed, aneurysm, or dissection. If headaches occur repeatedly with sexual activity over a long period, this problem is much less likely to be dangerous.
Stroke Caused by Blockage
A sudden blood vessel blockage caused by a blood clot or thrombosis, or from a cholesterol build-up, can result in a different kind of stroke. Ischemic strokes are caused by a lack of blood flow, but they do not include bleeding. Any stroke can cause immediate severe head pain, often with other symptoms such as weakness, problems with speech, sensation, consciousness, or vision. A thrombosis can occur in the veins surrounding the brain and be brought on by an injury or fall, or made more likely by certain medications (such as estrogen or testosterone) or an inherited tendency to form blood clots.
Head Injury Causing the Later Onset of a Severe Headache
Depending on the age of the individual, a severe headache can occur hours to days after a mild-to-moderate head injury. This can result in what is called an epidural hemorrhage or bleed (most common in younger patients) or a subdural hematoma or bleed (more common in older people).
A thrombosis, or clot in the veins surrounding the brain, can also be triggered by an injury. This is why even people who have already been to the emergency room, had a CT, and had normal neurological examinations will need to be re-evaluated immediately if they develop a new or worsening headache in the days following an injury. Additionally, you should follow up with your doctor if you find yourself developing any new weakness, decreased awareness, speech problems, or unusual symptoms after being injured.
Reversible Cerebral Vasoconstriction Syndrome
In this often difficult-to-diagnose disorder, there is a temporary narrowing or spasming of a blood vessel surrounding the brain. The resulting loss of blood flow, although not usually permanent, causes a sudden, very painful headache. This is often, but not always, accompanied by other symptoms such as temporary changes in vision, consciousness, strength, or sensation.
The cause of this phenomenon may be related to an individual’s blood vessels being prone to spasm, or the spasm may come from a medication like or from marijuana, cocaine, or stimulants. Reversible cerebral vasoconstriction syndrome (RCVS) can be difficult to diagnose without immediate magnetic resonance angiography (MRA)—really an MRI of the blood vessels—or CT angiogram (CTA)—basically a CT of the blood vessels.
Once the problem has resolved, the blood vessels can appear completely normal. Medications may be used to decrease the tendency for blood vessels to spasm, but the effectiveness of these treatments is not completely known. Avoiding substances that increase the likelihood of spasm may be the best option.
Inflammation of a Blood Vessel (Vasculitis)
Vasculitis, or blood vessel inflammation, comes from an autoimmune attack—that is, the body attacking its own blood vessels. The onset of this type of headache typically takes a little longer than the usual thunderclap headache, but there can be a similarly abrupt loss of vision or other sudden neurological symptoms.
If a person is over the age of 50 and has new pain on one side of their head or behind the eye, or if it hurts to chew, it is important to have these symptoms evaluated promptly. The most common form of vasculitis—giant cell arteritis, sometimes called temporal arteritis—is diagnosed through blood testing and a biopsy, and is treatable with steroid medications. Not treating giant cell arteritis can result in permanent loss of sight.
Sudden New Headaches in Pregnancy and Pituitary Apoplexy
In pregnancy, sudden new headaches may signal a number of different disorders, particularly late in pregnancy. Dangerous and unexpected elevations in blood pressure can signal a condition called eclampsia, which requires immediate evaluation and treatment.
During pregnancy or soon after delivery, the pituitary gland—which controls many important hormones—can bleed and cause changes in blood pressure, vision, and severe pain. This cause of thunderclap headache is called pituitary apoplexy.
Evaluating New Headache Pain: When Is a Sudden Headache Serious?
Sudden, extreme head pain—even without other symptoms—can serve as a warning of a larger bleed or stroke to come. Clues that this is a dangerous headache include neurological changes such as weakness, visual changes, trouble thinking, or unusual sensations. However, the biggest clue is the onset of a thunderclap headache.
If a patient is evaluated promptly, the problem can often be diagnosed with a CAT scan and a spinal tap or lumbar puncture, in which a sample of spinal fluid is withdrawn from the back and analyzed for the presence of blood. Alternatively, MRI and MRA or CTA imaging may be used during the later stages of a headache.
Healthcare providers will use these types of brain imaging technology to look for signs of anything wrong with the blood vessels in the brain. Problems may include any of those listed above, such as an outpouching of a blood vessel (aneurysm), a tear in a vessel (dissection), an inflammation of blood vessels (vasculitis), a small amount of blood in the brain (sentinel bleed) or other irregularities. With blockages, the part of the brain surrounding the clot will have an absence of blood flow and will be a different color.
How Do You Treat Thunderclap Headaches?
A new, sudden headache does not always signal a dangerous underlying disorder. If doctors find no specific cause after a medical examination, they may then start treatment for what is called primary thunderclap headache, which is considered benign.
If these headaches occur predictably at certain times, such as with sexual activity, then treating them with medication such as a non-steroidal anti-inflammatory (NSAID)—in particular, indomethacin—may be all that is needed. If the headaches are more frequent, a preventive medication taken on a daily basis may be useful. In the latter case, your doctor may prescribe something from the antihypertensive (blood pressure) class of medications.
Migraine With Aura vs. Stroke
Some patients with migraine may experience aura, which is typically temporary numbness, changes in vision, and, in a smaller number of people, weakness that comes before or during a migraine attack. The first time this occurs, it may be confused with a possible stroke, as the symptoms often mimic a blood vessel blockage or bleed. When this new, sudden and severe migraine occurs—and particularly if it is accompanied by neurologic changes—individuals will require immediate medical evaluation to rule out the possibility of a stroke.
It is difficult to know whether or not a sudden, severe headache is a sign of a dangerous underlying condition. For this reason, all first-time thunderclap headaches should be dealt with by seeking immediate medical evaluation to look for signs of more serious problems.
The American Migraine Foundation is committed to improving the lives of those living with this debilitating disease. For more of the latest news and information on migraine, visit the AMF Resource Library. For help finding a healthcare provider, check out our Find a Doctor tool. Together, we are as relentless as migraine.
