Aneurysm

Overview

An aneurysm is a bulge or ballooning in the wall of a blood vessel at a point where the wall has weakened. Normally, blood vessel walls are strong and flexible. But when one area weakens, the constant pressure of blood flowing through it causes that spot to swell outward — like a bubble forming on a worn bicycle tyre. As the bulge grows, the wall becomes thinner and thinner, until at some point it is at risk of rupturing.

The most dangerous thing about an aneurysm is that it usually causes no symptoms. Most aneurysms grow silently for years, and many people only find out they have one by chance, during an imaging test done for an entirely different reason. When an aneurysm ruptures, however, the situation becomes critical very quickly — internal bleeding develops rapidly and a life-threatening emergency is underway.

An aneurysm can form in almost any blood vessel in the body. The most common and most life-threatening types are the aortic aneurysm and the brain (intracranial) aneurysm. The aorta is the body's largest artery, carrying blood directly from the heart; an aneurysm there can develop in the abdomen or chest. Brain aneurysms form in the arteries that supply the brain, and when they rupture they cause a brain haemorrhage.

There is genuine good news: when an aneurysm is detected early through imaging and monitored regularly, the risk of rupture can be managed effectively. For aneurysms that have grown large or are expanding quickly, surgical or interventional treatment can prevent rupture before it happens.

Types of Aneurysm

There are several distinct types of aneurysm. Each develops in a different location, may produce different symptoms, and requires a different approach to management.

• Aortic aneurysm. The most common and most dangerous type. The aorta is the body's largest artery, running from the heart through the chest and abdomen. An abdominal aortic aneurysm (AAA) develops in the section of the aorta that passes through the abdomen and is especially common in men over 65. A thoracic aortic aneurysm affects the section within the chest. Both types usually remain silent for a long time.
• Brain (intracranial) aneurysm. A ballooning in one of the arteries supplying the brain. Most remain small and never cause symptoms. When one ruptures, however, it causes bleeding into the space around the brain (subarachnoid haemorrhage), producing sudden severe headache and potentially serious complications.
• Peripheral aneurysm. An aneurysm in the arteries of the legs, groin, or arms. The risk of rupture is lower than with aortic or brain aneurysms, but they are still important because clots can form inside them and travel to the leg, risking gangrene. Popliteal aneurysm (behind the knee) and femoral aneurysm (in the groin artery) are the most common peripheral types.
• Visceral aneurysm. An aneurysm in the arteries supplying the kidneys, spleen, liver, or intestines. Splenic artery aneurysm is the most common in this group and carries a particular risk of rupture in pregnancy.

Symptoms

The majority of aneurysms produce no symptoms at all. As they grow, they may press on surrounding structures, and if they rupture, symptoms develop suddenly and severely.

Abdominal aortic aneurysm symptoms can include:

• A dull ache around the navel or in the back. As the aneurysm enlarges, it can press on nearby structures and produce a persistent dull ache around the navel or in the lower back.
• A pulsing sensation in the abdomen. Some people notice a rhythmic throbbing or pulsing feeling in the centre of the abdomen.
• Rupture symptoms. Sudden, severe pain in the abdomen or back, a rapid drop in blood pressure, faintness, and shock are the signs of rupture. This is a medical emergency — call emergency services immediately.

Brain aneurysm symptoms can include:

• Unruptured aneurysm symptoms. Most small aneurysms cause no symptoms. Larger ones can press on nearby nerves or tissue, causing a drooping eyelid, double vision, pain around the eye, or facial numbness.
• The worst headache of your life. When a brain aneurysm ruptures, it causes sudden, extremely severe headache — a type and intensity that has never been felt before. People typically describe it as "the worst headache of my life" or "like being hit on the head." Stiff neck, sensitivity to light, nausea, vomiting, and altered consciousness may accompany it. This is a medical emergency — call emergency services immediately.

Thoracic aortic aneurysm symptoms can include:

• Chest or back pain
• Breathlessness or difficulty swallowing (if the aneurysm is pressing on the windpipe or oesophagus)
• Hoarseness (if pressing on the nerve that controls the vocal cords)

When to See a Doctor

Because most aneurysms cause no symptoms, screening is important for people at elevated risk.

Schedule a medical evaluation if:

• You are a man over 65 who smokes or has smoked — screening for abdominal aortic aneurysm is recommended
• A close family member has had an aneurysm
• You have Marfan syndrome or a connective tissue disorder
• You have developed unexplained persistent pain around the navel or in the back
• You have noticed a drooping eyelid, double vision, or numbness on one side of the face

Call emergency services immediately if:

• You develop sudden, extremely severe abdominal or back pain — especially accompanied by faintness or a drop in blood pressure
• You develop a sudden, extremely severe headache unlike any you have had before
• Severe headache is accompanied by a stiff neck, altered consciousness, or vomiting
• You develop sudden vision loss, facial weakness, or arm or leg weakness

Causes

Aneurysms begin with a weakening of the blood vessel wall. This weakening rarely has a single cause — it is usually the result of several factors working together over time.

• Atherosclerosis (hardening of the arteries). Cholesterol and fatty plaques accumulating in the vessel walls over many years weaken the wall and reduce its elasticity. This is the most common underlying cause of abdominal aortic aneurysm.
• High blood pressure. Persistently elevated blood pressure inflicts chronic mechanical stress on vessel walls. Over time, this thins the wall and creates the conditions for ballooning. High blood pressure both triggers aneurysm formation and accelerates the growth of an existing one.
• Genetic and connective tissue disorders. Inherited conditions such as Marfan syndrome and Ehlers-Danlos syndrome involve a structural weakness in the vessel wall from birth. People with these conditions can develop aneurysms at a much younger age and with faster progression.
• Infection and inflammation. Rarely, bacterial infections or inflammatory diseases affecting the vessel wall can predispose to aneurysm formation. These are sometimes called mycotic aneurysms.
• Trauma. Serious injuries — such as those sustained in a road traffic accident or a fall from a height — can damage the vessel wall and lead to aneurysm formation.
• Congenital vessel abnormalities. Brain aneurysms sometimes arise from a structural weakness in the artery wall that has been present since birth. This is one reason why screening is recommended for people with a family history of brain haemorrhage.

Risk Factors

The established risk factors for aneurysm include the following:

• Smoking. The single most important modifiable risk factor for aneurysm. Tobacco directly damages vessel walls and accelerates atherosclerosis. It increases the risk of abdominal aortic aneurysm three to five times compared to non-smokers. It also speeds up the rate at which an existing aneurysm grows.
• Older age. The risk of aneurysm increases with age. Abdominal aortic aneurysm is particularly common after 65, as vessel walls naturally weaken and lose elasticity over time.
• Male sex. Abdominal aortic aneurysm is four to six times more common in men than in women. Brain aneurysms, however, are slightly more prevalent in women.
• High blood pressure. Uncontrolled hypertension both triggers aneurysm formation and drives its growth.
• Family history. Having a close family member with an aneurysm significantly raises personal risk. Genetic predisposition plays a particularly strong role in abdominal aortic aneurysm.
• High cholesterol and atherosclerosis. Arterial hardening is one of the core mechanisms behind aneurysm formation.
• Connective tissue disorders. Marfan syndrome and Ehlers-Danlos syndrome cause structural weakness in vessel walls and predispose to aneurysm development at a younger age.

Diagnosis

Because most aneurysms cause no symptoms, they often go undetected unless screening is performed or they are found incidentally during imaging done for another reason.

Methods used to diagnose aneurysms include the following:

• Ultrasound scan. The first-choice method for screening abdominal aortic aneurysm. It involves no radiation, is painless, and is highly reliable. National screening programmes in many countries offer abdominal ultrasound to men in specific age groups.
• CT angiography. Provides very detailed images of the aneurysm's size, shape, location, and relationship to surrounding blood vessels. The most valuable imaging method when surgical or interventional treatment is being planned, and also provides fast, reliable information in emergencies.
• MRI. Particularly useful for brain and thoracic aortic aneurysms. Involves no radiation and produces excellent soft-tissue images.
• Cerebral angiography. A thin catheter is passed through the groin into the brain's arteries, contrast dye is injected, and X-ray images are taken. Still considered the gold standard for precise visualisation of brain aneurysms. Treatment (coiling) can often be performed in the same procedure.
• Physical examination. Some abdominal aortic aneurysms can be felt as a pulsatile mass during abdominal examination, but this is not a reliable method. Physical examination provides supporting information but diagnosis must always be confirmed by imaging.

Treatment

Treatment depends on the aneurysm's size, how quickly it is growing, its location, and the patient's overall health. Not every aneurysm needs immediate treatment — small, stable aneurysms are often safely managed with monitoring alone.

Treatment options for aneurysm include the following:

• Regular monitoring with imaging. For small aneurysms (generally below 5 cm for abdominal aortic aneurysm), regular ultrasound or CT scans track the size and growth rate. As long as rupture risk remains low, intervention is deferred. Controlling risk factors — particularly quitting smoking and managing blood pressure — is critically important during this period.
• Medication. Medication does not eliminate an aneurysm but can slow its growth and reduce rupture risk. Blood pressure medications (beta-blockers, ACE inhibitors) reduce the pressure the blood exerts on the vessel wall. Statins slow the progression of atherosclerosis. Smoking cessation is the most critical component of non-surgical aneurysm management.
• Open surgical repair. The affected section of the vessel is exposed through surgery, the weakened segment is removed, and a synthetic graft is sewn in to restore blood flow. This produces very durable long-term results. However, it is a major operation with a longer recovery period, and surgical risk is higher in elderly or medically frail patients.
• Endovascular repair (EVAR/TEVAR). A thin catheter is passed through the groin or arm and a stent-graft — a metal-supported fabric tube — is placed inside the aneurysm. This tube redirects blood flow away from the weakened wall, removing the pressure that drives expansion. It is far less invasive than open surgery, recovery is much quicker, and it is particularly suited to older or higher-risk patients. It does require long-term imaging follow-up and is not suitable for every aneurysm anatomy.
• Brain aneurysm treatment: coiling (endovascular coil embolisation). A thin catheter is guided through the groin into the aneurysm. Small metal coils are deposited inside the aneurysm sac, promoting clot formation and preventing blood from filling it. This minimally invasive technique has a much shorter recovery time than open brain surgery.
• Brain aneurysm treatment: surgical clipping. A metal clip is placed across the neck of the aneurysm through brain surgery (craniotomy), cutting off its blood supply and effectively deactivating it. More invasive than coiling, but for certain aneurysm types it may produce a more permanent result.

Complications

Rupture is the most feared and most serious complication of an aneurysm. But other important complications can also develop.

• Rupture and internal bleeding. When an aneurysm ruptures, rapid and severe internal bleeding follows. A ruptured abdominal aortic aneurysm has a very high mortality rate — even with rapid surgery, the chances of survival are significantly reduced. A ruptured brain aneurysm causes brain haemorrhage and can result in severe, permanent neurological damage.
• Clot formation and embolism. Blood can stagnate inside the aneurysm sac and form clots. These clots can break off and travel to smaller vessels, causing tissue death in the legs (gangrene) or blockages in the arteries supplying organs.
• Pressure on surrounding structures. A growing aneurysm can compress adjacent organs. A thoracic aortic aneurysm may press on the oesophagus or windpipe, causing difficulty swallowing or breathlessness.
• Dissection. A related condition in which the inner lining of the aorta tears, allowing blood to force its way between the layers of the vessel wall. It presents with sudden, very severe pain and is a medical emergency.

Living with an Aneurysm

Being diagnosed with an aneurysm can feel alarming. But many people with monitored, stable aneurysms and well-controlled risk factors live a completely normal life.

Control Your Risk Factors

Quitting smoking is the single most effective step you can take in managing an aneurysm. Smoking both accelerates growth and increases rupture risk. Monitor your blood pressure regularly and work with your doctor to keep it within a healthy range — high blood pressure is one of the most important drivers of aneurysm growth. Managing cholesterol and diabetes slows the atherosclerotic process that underlies most aneurysms.

Do Not Miss Follow-up Appointments

Regular imaging appointments are vitally important for monitored aneurysms. As an aneurysm grows toward the threshold for intervention, catching that growth in time allows treatment to be planned carefully and safely. Missing surveillance scans risks allowing significant growth to go unnoticed.

Physical Activity

Moderate exercise is generally safe with a small, stable aneurysm. However, heavy lifting, straining, and sudden intense exertion can cause abrupt blood pressure spikes that place dangerous stress on the aneurysm wall. Discuss your specific activity limits with your doctor.

Know the Warning Signs

Both you and those close to you should be able to recognise rupture symptoms. Sudden, severe abdominal or back pain, or a sudden severe headache unlike anything previously experienced, mean calling emergency services immediately without waiting. Recognising and acting on these signs quickly can save a life.

Preparing for Your Appointment

Coming prepared to your appointment helps both the diagnostic process and treatment decision-making.

What you can do:

• Bring any previous imaging results and reports if you have them
• Mention any family history of aneurysm, aortic surgery, or brain haemorrhage
• Describe your smoking history honestly
• List all current medications
• Mention any chronic conditions such as high blood pressure, diabetes, or high cholesterol
• Write your questions down in advance

Questions you may wish to ask your doctor:

• How large is the aneurysm and is it dangerous right now?
• How quickly is it growing?
• How often will I need follow-up imaging?
• At what size or growth rate would treatment become necessary?
• Which symptoms mean I should go to the emergency department immediately?
• Which physical activities should I avoid?
• Should my family members be screened?

Questions your doctor may ask:

• Do you smoke or have you smoked in the past?
• Do you have high blood pressure and is it under control?
• Is there a family history of aneurysm, aortic surgery, or sudden cardiovascular death?
• Have you had any relevant imaging done before?
• Are you experiencing any pain around the abdomen or back?
• What medications are you currently taking?