Subarachnoid haemorrhage: symptoms, causes, treatment and recovery

The NHS lists the main symptoms of a subarachnoid haemorrhage, which can come on within seconds. It says the haemorrhage can happen at any time, but may be more likely when coughing, going to the toilet, lifting something heavy or having sex.

• An extremely painful headache that starts suddenly and does not go away, called a thunderclap headache.

• Neck pain or a stiff neck.

• Feeling or being sick.

• Being very sensitive to light.

• A seizure (fit) or shaking uncontrollably.

• Fainting, feeling sleepy or drowsy, or being confused.

• Drooping on one side of the face, slurred speech or weakness on one side of the body.

The NHS says to call 999 if you or someone with you gets a sudden headache that is extremely painful and does not go away, has face weakness, weakness or numbness in one arm or down one side of the body, speech problems such as slurring or confusion, or blurred vision or loss of sight in one or both eyes. It specifically advises not to drive yourself to A&E; the person you speak to at 999 will advise what to do. Do not wait to see if it settles, and do not take a sudden severe headache to be an ordinary migraine without being checked.

The brain is covered by protective layers, and the subarachnoid space lies between the inside of the skull and the brain, carrying small blood vessels. A subarachnoid haemorrhage happens when one of these vessels bleeds into that space. The NHS classifies it as a type of stroke, specifically a haemorrhagic one, in which bleeding rather than a blocked artery damages the brain.

It is rare, and the NHS states that it is a life-threatening emergency. Rapid treatment in hospital matters because the bleed itself, and the complications that can follow, can cause lasting harm. Unlike the more common type of stroke caused by a clot, the main warning sign is often a dramatic headache rather than weakness or speech change, although those can also occur.

According to the NHS, most subarachnoid haemorrhages are caused by a burst brain aneurysm. There is not always an obvious reason why a person has one: some people have them from birth, others develop them later, and having close relatives with brain aneurysms can make them more likely. The NHS stresses that most brain aneurysms never cause problems, and that bleeding is rare.

The NHS page on brain aneurysms lists factors that increase the chance of developing one: smoking, high blood pressure, a close relative who has had one, injury to a blood vessel in the brain, taking drugs such as cocaine, and certain genetic conditions such as autosomal dominant polycystic kidney disease or Ehlers-Danlos syndrome. Other causes of subarachnoid bleeding are severe head injury and arteriovenous malformations.

No. NICE says a thunderclap headache (a sudden severe headache, typically peaking in intensity within 1 to 5 minutes) is a red-flag symptom of subarachnoid haemorrhage, but that it is also associated with other conditions or causes such as migraine, cough, sex or exertion. Most people with a thunderclap headache do not have a subarachnoid haemorrhage.

NICE is clear, though, that this should not deter further investigation if a subarachnoid haemorrhage is suspected, and that people with subarachnoid haemorrhage can present with a range of non-specific symptoms and signs and are at greater risk of the diagnosis being missed. The NHS headache advice also says to call 999 or go to A&E if a headache started suddenly and is extremely painful.

NICE says people with suspected subarachnoid haemorrhage seen outside hospital should be referred to an emergency department immediately. In hospital, an urgent non-contrast CT head scan is the first test, and a subarachnoid haemorrhage is diagnosed if the scan shows blood in the subarachnoid space. NICE notes that the accuracy of CT is highest within 6 hours of symptom onset.

If a CT scan done more than 6 hours after symptoms started shows no bleed, NICE says a lumbar puncture (a needle test of the fluid around the spine) can be considered, at least 12 hours after symptom onset. A bleed is diagnosed if the sample shows raised bilirubin (xanthochromia).

Once a bleed is confirmed, NICE says a CT angiogram of the head should be offered without delay to look for the cause, usually an aneurysm, and to guide treatment. If that does not find the cause, further imaging such as digital subtraction angiography or MR angiography may be considered.

The NHS says the main treatment for a subarachnoid haemorrhage is surgery to stop the bleeding. There are two approaches, and the surgeon discusses with you which is most suitable where possible.

The NHS says how a subarachnoid haemorrhage affects life varies from person to person and depends on where in the brain the bleeding happened and how much damage it caused. People may experience seizures, heart, lung or liver problems, difficulties with memory, concentration and communication, depression and mood changes, fatigue, headaches and unusual sensations. A small number develop epilepsy.

Follow-up includes regular reviews to look for complications such as a build-up of fluid around the brain (hydrocephalus) or other aneurysms, and advice on driving, work, exercise, travel and sex. Rehabilitation may include physiotherapy, speech and language therapy, cognitive behavioural therapy for mood changes and cognitive exercises for memory and concentration. The NHS notes that recovery can be slow and frustrating, and that some long-term problems can keep improving for months or years.

Emotional support matters too. The NHS points to the Stroke Association and to local and online groups of people who are recovering from the same condition.

A suspected subarachnoid haemorrhage is an emergency and is dealt with through 999 and an NHS emergency department. NICE says the need for transfer to a specialist neurosurgical centre should be urgently discussed once the diagnosis is made, because the risk of rebleeding is highest within 24 hours of the onset of symptoms.

During recovery the NHS says you will have regular follow-ups with your doctor and recovery team and may have rehabilitation such as physiotherapy, speech and language therapy and cognitive behavioural therapy. Some people also use private rehabilitation or counselling alongside this. Ask any provider how it will coordinate with your NHS team, and about driving, which your doctor will advise on.