What does a ruptured brain aneurysm feel like?

A sudden, extremely severe headache that peaks within seconds to a minute — often called the "worst headache of my life" — commonly with neck stiffness, vomiting, light sensitivity, and sometimes collapse or loss of consciousness. Call 995 immediately.

I have an unruptured aneurysm but no symptoms — is that normal?

Yes. Most unruptured aneurysms cause no symptoms and are found by chance. Your doctor assesses the rupture risk from its size, shape, location and your risk factors, then advises monitoring or treatment.

What causes brain aneurysms?

A weak spot in an artery wall, made more likely by high blood pressure, smoking, older age, a family history, and inherited conditions such as polycystic kidney disease.

How is a brain aneurysm treated?

By securing it with coiling (minimally invasive, via a catheter) or clipping (open surgery). A ruptured aneurysm is an emergency treated urgently; small unruptured ones may instead be monitored with scans.

Can I lower my risk of a brain aneurysm rupture?

You can reduce the risk by controlling blood pressure, stopping smoking and limiting heavy alcohol use. People with a strong family history or polycystic kidney disease should discuss screening with their doctor.

Brain Aneurysm & Subarachnoid Haemorrhage (Singapore)

Written & reviewed by the BestDoctors.sg editorial team · Last updated 1 Sep 2026 · General information, not medical advice

Quick answer. A brain (cerebral) aneurysm is a bulge or ballooning in a weak spot of an artery wall in the brain. Most unruptured aneurysms cause no symptoms and are found by chance on scans done for other reasons. The danger is rupture, which causes a subarachnoid haemorrhage (bleeding around the brain) – a life-threatening emergency. Its hallmark is a sudden, extremely severe “thunderclap” headache – often the worst headache of one’s life – frequently with neck stiffness, vomiting, sensitivity to light, and collapse or loss of consciousness. If this happens, call 995 immediately.

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In a medical emergency, or for severe or sudden symptoms such as breathing difficulty, chest pain, fainting or stroke signs, call 995 immediately.

Emergency – call 995 now. A sudden, severe headache – the worst you have ever had, coming on like a “thunderclap” within moments – is a medical emergency, especially with neck stiffness, vomiting, sensitivity to light, blurred or double vision, drowsiness, a fit (seizure), or stroke-like weakness or slurred speech. Do not wait to see whether it settles, do not drive yourself, and do not lie down and hope it passes. A burst brain aneurysm is life-threatening and every minute counts – call 995 or go straight to the nearest A&E.

Most brain aneurysms never cause trouble, but a rupture is a true emergency where minutes matter. The single most important thing to recognise is the sudden, worst-ever headache.

What a brain aneurysm is

An aneurysm is a swelling where an artery wall has a weak spot and balloons out, most often where brain arteries branch and the wall is naturally thinner. Blood pressure pushing against that weak point can, over time, make the swelling stretch and grow. Many aneurysms stay small and never cause any problem – a person may carry one for a lifetime without knowing. The concern is that a weakened wall can leak or burst. When one bursts (ruptures), blood escapes into or around the brain, most often into the fluid-filled space that surrounds it – a subarachnoid haemorrhage – which raises pressure inside the skull, starves brain tissue of blood and oxygen, and is life-threatening. Understanding the difference between an aneurysm that is simply present (unruptured) and one that has burst (ruptured) is the key to this condition.

Unruptured aneurysms – usually silent

Most unruptured aneurysms cause no symptoms and are discovered incidentally on brain scans done for other reasons, such as headaches, dizziness or an unrelated complaint. Because they are silent, they are not something a person can feel for or check at home. A large unruptured aneurysm can press on nearby structures and cause warning signs: a persistent or unusual headache, vision changes or double vision, pain above or behind an eye, a drooping eyelid or dilated pupil, or numbness on one side of the face. A new eye, pupil or facial sign warrants urgent assessment, because it can mean an aneurysm is enlarging, pressing on a nerve, or leaking. Occasionally a person notices a brief, unusually severe headache in the days or weeks before a major rupture – a so-called sentinel or warning headache caused by a small leak. Any sudden, severe or out-of-character headache should be taken seriously rather than dismissed.

Rupture and subarachnoid haemorrhage – the emergency

Rupture bleeds into the space around the brain (a subarachnoid haemorrhage) and is life-threatening. The classic symptom is a sudden, extremely severe “thunderclap” headache that reaches maximum intensity almost at once – the “worst headache of my life.” It is often accompanied by a stiff neck, nausea and vomiting, sensitivity to light, blurred or double vision, drowsiness or confusion, a brief loss of consciousness or collapse, a seizure, or stroke-like weakness, numbness or slurred speech. Some people describe feeling as though they were struck on the back of the head. The bleeding can worsen quickly, and a person who seems to recover after the first headache can deteriorate again, so any such headache needs emergency care even if it eases. Most non-traumatic subarachnoid haemorrhages are caused by a ruptured aneurysm. Call 995 immediately – don’t wait to see if the headache settles, and don’t let the person go to sleep it off.

Causes and who is at higher risk

The weak spot in an artery wall may be present from birth or develop over the years. Several factors make an aneurysm more likely to form, grow or burst. High blood pressure and smoking are the leading modifiable risks – both stress and weaken artery walls, and smoking is strongly linked to rupture. Others include a family history of brain aneurysm (particularly in a parent, brother or sister), increasing age, being female, and heavy alcohol use or stimulant drug use such as cocaine or amphetamines. Certain inherited conditions also raise the risk – notably autosomal dominant polycystic kidney disease and some connective-tissue disorders that affect the strength of blood-vessel walls. Having one or more of these does not mean an aneurysm will ever form or burst, but it is a reason to keep blood pressure well controlled and to mention any strong family history to a doctor.

How it’s diagnosed

When a rupture is suspected, diagnosis is urgent. An emergency CT scan of the brain detects most bleeds quickly and is usually the first test. If the CT is normal but a haemorrhage is still suspected, a lumbar puncture (a sample of the fluid from the lower back) may be taken to look for blood in the spinal fluid. Once bleeding is confirmed, or when an aneurysm is being assessed, CT angiography or MR angiography maps the blood vessels to show the aneurysm’s size, shape and position. A catheter cerebral angiogram – in which a fine tube is guided through an artery to inject dye directly into the brain vessels – gives the most detailed pictures and can guide treatment in the same setting. Unruptured aneurysms are often first spotted by chance on a scan and then characterised with these same vessel-imaging tests. In Singapore, this assessment is led by a neurosurgeon or neurologist, often at a specialist centre such as the National Neuroscience Institute.

Treatment

A ruptured aneurysm is a neurosurgical and neurointerventional emergency. The aneurysm must be secured quickly to prevent a second, often more dangerous, bleed, alongside intensive care to manage blood pressure, breathing, brain pressure and complications. Two main methods secure it. Endovascular coiling is minimally invasive: a catheter is passed from a groin or wrist artery up into the brain to pack the aneurysm from the inside with fine coils so blood can no longer enter it. Surgical clipping is open surgery in which a small clip is placed across the neck of the aneurysm to seal it off. Both are available at Singapore’s National Neuroscience Institute, and the choice depends on the aneurysm’s size, shape and location and the person’s overall condition. For an unruptured aneurysm found by chance, the team weighs the risk of rupture against the risks of treatment. Some – especially small, stable ones – are simply monitored with periodic scans, while those judged higher-risk are treated. This is an individual decision made together with the specialist.

Recovery and outlook

A ruptured aneurysm can have lasting effects. Some people recover well, while others are left with problems such as fatigue, headaches, difficulty with memory or concentration, mood changes, or weakness – and rehabilitation with physiotherapy, occupational therapy, speech therapy and psychological support is often part of getting back to daily life. Recovery can be gradual, and support for both the person and their family matters. For someone with an unruptured aneurysm that is being monitored or has been treated, the focus is on controlling risk factors and keeping to follow-up scans and appointments so any change is picked up early.

Prevention and reducing your risk

An aneurysm cannot always be prevented, but the chance of one forming, growing or bursting can be lowered. The most important steps are keeping blood pressure well controlled, stopping smoking, and moderating alcohol. Avoiding stimulant drugs, staying physically active within your doctor’s advice, and attending any recommended follow-up for a known aneurysm all help. If you have a strong family history of brain aneurysm or an inherited condition such as polycystic kidney disease, discuss this with your doctor, who can advise whether screening is appropriate for you. Reliable self-help information for Singapore residents is available through HealthHub.

When to seek emergency help

Call 995 immediately for a sudden, severe “worst-ever” or thunderclap headache, particularly with neck stiffness, vomiting, sensitivity to light, blurred or double vision, drowsiness or confusion, a fit, collapse, or stroke-like weakness or slurred speech. Do not wait, do not drive yourself, and do not lie down to sleep it off – a burst brain aneurysm is life-threatening and every minute counts. Seek urgent medical assessment, too, for a new eye or pupil change, a drooping eyelid, or a new persistent headache that is unusual for you, as these can be warning signs of an enlarging or leaking aneurysm.

Related brain & nerve conditions

Sources

NHS — brain aneurysm (definition; incidental finding; unruptured pressure symptoms; rupture symptoms; risk factors including polycystic kidney disease; treatment; prevention).
StatPearls / Mayo Clinic Proceedings — subarachnoid haemorrhage (most non-traumatic cases from aneurysm rupture; thunderclap headache; workup).
National Neuroscience Institute (NNI), Singapore — national neuroscience centre offering both coiling and clipping (Singapore context).

General information only. This guide is general information about a brain or nerve condition and is not a diagnosis or personalised medical advice. See a doctor — a GP or a neurologist — for assessment, tests and treatment. Call 995 for stroke symptoms (face drooping, arm weakness, slurred speech), a sudden severe “worst-ever” headache, a first or prolonged seizure, or a rapidly worsening loss of movement, consciousness or breathing.

Brain Aneurysm & Subarachnoid Haemorrhage in Singapore