What is a thunderclap headache and what does it feel like?

What is a thunderclap headache?

When you experience a headache, deciding whether it's worth a trip to the doctors can be a bit of a headache in itself. One of the most important indicators is how severe and incapacitating your headache is.

A thunderclap headache comes on very suddenly and is very painful. GP and mental health coach Dr Hana Patel explains why you should see a doctor if you think you have one:

"This may be a sign of a life-threatening headache, and this should be investigated - especially when the headache develops over a few minutes and in people with no previous history of having headaches." In these cases, you should call an emergency ambulance.

What causes thunderclap headaches?

For some people who have thunderclap headaches there's no obvious cause and the people who experience them are healthy. However, Dr Patel explains that in other cases they are caused by serious conditions involving bleeding in the brain. For this reason, they should be considered a medical emergency.

The most important¹ of these conditions is a subarachnoid haemorrhage - an uncommon life-threatening form of stroke where bleeding occurs between the brain and its surrounding membrane.

The second most common² dangerous cause of thunderclap headaches are reversible cerebral vasoconstriction syndromes. In these rare group of conditions, the blood vessels in the brain suddenly tighten. Again, these should be seen as a medical emergency.

There are several other possible brain-related causes. These are all dangerous, but an early diagnosis may improve your chances of recovery.

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What does a thunderclap headache feel like?

This is a sudden and severe headache that lives up to its name, striking like a clap of thunder in your head or neck. People often say it feels like they have been suddenly punched in the back of the head. This can happen after certain triggers - such as sexual activity - or have no trigger at all.

Thunderclap headaches may or may not also be accompanied by other warning signs, including:

• Nausea or vomiting.

• Feeling drowsy or fainting.

• Fever.

• Seizures.

• The pain extending down to your neck.

• Muddled thinking.

• Slurred speech like you are drunk.

• Difficulty walking in a straight line.

• Having limb weakness.

• Feeling like the room is spinning.

How long does a thunderclap headache last?

Thunderclap headaches tend to reach their most painful point within 30 to 60 seconds of starting³, but this doesn't mean they're short-lived. It's common for these headaches to take around an hour to disappear after peaking, and in some cases they can last for many hours or even for a week or more.

The importance of seeing a doctor

If your headache is the worst you have ever had - very severe and sudden - call for an ambulance immediately. At the hospital, they may run tests such as a computed tomography (CT) scan of your brain, a magnetic resonance imaging (MRI) brain scan, or a spinal tap - also called a lumbar puncture.

The sooner you have a diagnosis, the better chances you have of recovery. Treatment will depend on the cause of your thunderclap headache, if one is identified.

Further reading

1. Ducros and Bousser: Thunderclap headache.

2. Ravishankar: Looking at thunderclap headache differently? Circa 2016.

3. Sekhon et al: Thunderclap headache.