Cerebral amyloid angiopathy (CAA): An explanation for patients and families

What is cerebral amyloid angiopathy?

Cerebral amyloid angiopathy, often shortened to CAA, is a condition that affects the small blood vessels in the brain. In CAA, a protein called amyloid builds up in the walls of these blood vessels over time. This makes the vessel walls more fragile than normal.

CAA is not an infection, not a cancer, and not caused by anything you did. It is a condition that becomes more common with ageing.

Why does amyloid build up?

Amyloid is a protein that is produced naturally in the body. In most people it is cleared away without causing problems. In CAA, amyloid is not cleared properly from the brain’s blood vessels and gradually accumulates.

Doctors do not yet fully understand why this happens in some people and not others. Age is the strongest risk factor. CAA is sometimes seen alongside memory problems or dementia, but it can also occur in people without memory symptoms.

What problems can CAA cause?

Because amyloid makes blood vessels more fragile, CAA mainly affects the brain by increasing the risk of bleeding.

Possible effects include:

• Small bleeds in the brain, often found on brain scans and sometimes causing no obvious symptoms
• Larger brain haemorrhages, which can cause sudden symptoms such as weakness, speech problems, confusion, or collapse
• Transient episodes, sometimes called “amyloid spells”, which can cause brief sensory symptoms (such as tingling or visual changes) or weakness
• Headaches, in some people
• Cognitive symptoms, such as difficulties with thinking or memory, particularly if there have been repeated small bleeds

Not everyone with CAA will experience all—or even any—of these problems.

How is CAA diagnosed?

CAA is usually suspected from brain imaging, especially MRI scans, which can show a pattern of small bleeds typical of the condition.

Doctors diagnose CAA based on:

• Your symptoms
• Brain scans
• Your age
• Excluding other possible causes of bleeding

A definite diagnosis would require examining brain tissue, but this is rarely needed or appropriate. In most cases, doctors can be confident about the diagnosis without this.

Is CAA the same as Alzheimer’s disease?

CAA and Alzheimer’s disease both involve amyloid, but they are not the same condition.

• Alzheimer’s disease mainly affects brain cells involved in memory and thinking
• CAA mainly affects blood vessels in the brain

Some people have both conditions, but many have CAA without Alzheimer’s disease.

How is CAA treated?

At present, there is no treatment that removes amyloid from brain blood vessels.

Care focuses on reducing risks and managing symptoms, including:

• Careful control of blood pressure, which reduces bleeding risk
• Review of blood‑thinning medicines (such as anticoagulants or antiplatelet drugs), as these can increase the risk of bleeding in some people
• Treatment and rehabilitation if a brain bleed or stroke‑like event has occurred
• Support for memory or thinking problems if present

Your healthcare team will balance the benefits and risks of any treatment carefully and tailor decisions to you as an individual.

What does this mean for the future?

CAA is a long‑term condition. In some people it remains stable for many years; in others, symptoms may progress gradually.

Having CAA does not mean that severe problems are inevitable. Many people continue to live independently, especially with good management of risk factors such as blood pressure.

Your doctor will discuss:

• Your individual level of risk
• What symptoms to watch for
• When to seek urgent medical help (such as sudden weakness, speech problems, or confusion)

Living with CAA

If you have been diagnosed with CAA, it can help to:

• Attend regular medical reviews
• Keep blood pressure well controlled
• Discuss any new medications with your doctor
• Seek support if you experience memory, mobility, or emotional changes

Support from family, carers, and healthcare professionals can make a significant difference.