CAA is short for cerebral amyloid angiopathy. This is a condition in which a protein called amyloid-beta builds up in the walls of small blood vessels in the brain.

Individuals with CAA experience different symptoms. These can include one or more of the following:

• Stroke: CAA can cause strokes, and more specifically strokes caused by bleeding in the brain. This type of stroke is called ‘intracerebral hemorrhage’. Individuals with this form of stroke will have different symptoms depending on which part of the brain is affected. Symptoms might include weakness of the face, arm and/or leg; loss of sensation involving the face, arm and/or leg; difficulties with speech; loss of vision; headache; fits or seizures; vomiting; confusion. The symptoms of a stroke can improve with rehabilitation, but some can be permanent.
• Cognitive impairment or dementia: CAA can cause problems with memory, thinking processes, language and/or behavior in some people.
• Transient focal neurological episodes or ‘amyloid spells’: These are episodes which come and go (are ‘transient’), and individuals make a full recovery and are symptom-free between episodes. Symptoms can include numbness, tingling and other changes in sensation, weakness, speech difficulties, and/or visual changes. These symptoms can come on over minutes, and can spread, for example initially involving the hand, then moving up to involve the whole arm and then the face. This particular symptom can be associated with episodes of bleeding on the surface of the brain, called convexity subarachnoid hemorrhage.

The most common form of CAA is called ‘sporadic CAA’. This is associated with increasing age, but at present we cannot predict who will develop this type of CAA. There are rare types of CAA associated with specific recognized causes, such as:

• Genetic CAA, also called familial CAA or inherited CAA: CAA can sometimes run in families, and this is called familial or genetic or inherited CAA. In these families, individuals may carry a gene mutation that causes CAA. People affected by the gene mutation often develop symptoms of CAA at a younger age than those affected by sporadic CAA (under the age of 55 years). The most well-known form of genetic CAA is called ‘Dutch-type CAA’. See for more information on Dutch-type CAA: https://www.hchwa-d.nl/en/what-is-hchwa-d
• Iatrogenic CAA: Iatrogenic means caused by medical intervention, and individuals with this form of CAA have previously had certain operations or treatments, often three or four decades before their symptoms of CAA started. This form of CAA is thought to happen because the amyloid-beta protein that causes CAA was transferred during these earlier medical procedures, either through cadaveric material, or certain hormone treatments.
• CAA-related inflammation: In this form of CAA, there is inflammation (an immune system response) surrounding the blood vessels in the brain that contain the amyloid-beta protein. Individuals with this form of CAA can have very rapidly developing symptoms, which can include: fits or seizures; headache; confusion and behavioral changes; drowsiness; strokes. Because this type of CAA is associated with inflammation, patients are often treated with medications that dampen down the immune system, for example steroids.

Your doctor will diagnose CAA using specific criteria. They will consider your symptoms and also the findings on your brain scan (usually an MRI scan). Individuals with CAA have certain changes on their brain scans which are suggestive of the condition but might not have otherwise caused any obvious symptoms. These changes include: cerebral microbleeds, cortical superficial siderosis, white matter hyperintensities, and enlarged perivascular spaces. In individuals who have unusual symptoms, or CAA at an age younger than expected, additional tests might be needed. This is to look for rare forms of CAA. Tests might include a lumbar puncture (which involves taking a sample of the fluid that surrounds the brain and spinal cord), an amyloid-PET scan (which looks directly for the presence of the amyloid protein that causes CAA in the brain) and/or genetic tests.

At the moment there is unfortunately no cure available for CAA, neither is there a reliable way of preventing CAA from happening. Treatment for individuals with CAA is focussed on reducing the risk of having future strokes. This will include treating your blood pressure (often with a lower blood pressure target than for people who do not have CAA) and avoiding medications which increase the risk of bleeding where possible.

Yes. Please scroll to the bottom of this page for an interactive map to identify a clinician with expertise in CAA in your geographical area.

Please see the answer to question nr. 4 ‘How is CAA diagnosed?’

Please see the answer to question nr. 3 ‘What are the different types of CAA?’

Alzheimer’s disease and CAA are caused by the same amyloid-beta protein. In Alzheimer’s disease the amyloid-beta protein is found around brain cells (neurons), whereas in CAA this amyloid-beta protein is found in the walls of small blood vessels. Individuals with Alzheimer’s disease also have a build-up of another protein, called tau, which is not frequently seen in CAA. In studies where scientists have looked at the brains of patients after they have died, there is evidence that both Alzheimer’s disease and CAA overlap, with many showing evidence of both conditions. However, we do not know why some individuals go on to have strokes (and CAA), and others develop dementia (and Alzheimer’s disease).

There is an overlap between CAA and Alzheimer’s disease, and some individuals can have evidence of both conditions. At present, we do not know which factors determine whether someone with CAA will go on to develop Alzheimer’s disease. Patients with CAA can also develop another type of dementia, called vascular dementia, which is caused by the damage to the brain’s blood vessels.

Most individuals with CAA do not need a genetic test, as they will have the sporadic type of CAA. However, if you have developed CAA at a younger age than is usual (under the age of 55 years), or there are other people in your family affected by CAA or dementia, or if you have symptoms that are unusual for CAA, you might be offered a genetic test.

The genetic forms of CAA are very rare. The most common genetic form of CAA is called ‘Dutch-type CAA’ (formerly known as HCHWA-D). More information on this type of CAA and additional resources can be found on the HCHWA-D Association website: https://www.hchwa-d.nl/en/.

Genetic testing will be offered by your doctor if appropriate. As this test might have implications for other people in your family, you might be offered genetic counselling (where these implications are discussed) and you might be asked to provide formal consent for these samples to be taken. The test itself involves providing a blood sample, similar to other blood tests you might have had in the past.

The amyloid in CAA is made of smaller building blocks of a protein called amyloid-beta. These amyloid-beta building blocks stick together, forming abnormal deposits which are difficult for the body to break down. It is these abnormal and difficult-to-break-down deposits that then build up in the walls of blood vessels in CAA. There are other amyloid diseases where amyloid protein is found in other organs of the body (such as the heart, kidneys, and liver) but these are not associated with amyloid-beta, and instead are caused by different amyloid building blocks.

We are not completely certain why CAA leads to strokes (and more specifically, bleeding in the brain). We believe that the presence of amyloid-beta in the walls of blood vessels affects their structure, making them more prone to leaking blood. We believe that the brain is able to tolerate small leakages (which is why we can see cerebral microbleeds on the brain scans of individuals with CAA, which are not associated with any obvious symptoms), but sometimes these leakages are large and cause bleeding strokes.

CAA is a type of amyloidosis. Amyloidosis means any disease in which amyloid proteins build in up the body. These amyloid proteins can be made up of different building blocks and can affect different organs of the body, including the heart, kidneys, and liver. CAA refers to amyloidosis within the walls of blood vessels of the brain – the most common form is due to amyloid-beta.

We do not know exactly how long CAA takes to build up, but we believe it is a process that takes many years (decades).

At present, we do not know of any ways of preventing CAA. As with many conditions that occur in older individuals, it is recommended to keep a healthy lifestyle, which includes exercise, a healthy diet, avoidance of smoking and excess alcohol intake, as these factors have been linked to increased vascular health.

At present, there is no cure for CAA.

We still do not know why CAA develops in some people, and research is underway to understand these processes better, so that we can identify targets that will allow CAA to be treated. We are also looking for ways in which CAA can be diagnosed earlier in the disease, at a stage at which it might be more reversible (many individuals are diagnosed only after they have had a stroke). These measures (called biomarkers) would help future treatment trials, as they could be used to see whether a treatment is working.

There is a huge amount of research being carried out in CAA. Below are some examples:

• Research involving animals:
  • This type of research aims to establish the processes that lead to CAA. Animal research involves experimental models of CAA, which are often mice or rats which have been bred to have specific genes that are known to cause the production of the human version of amyloid-beta. As a result, these animals develop CAA in a way similar to people. These models can also be used to test potential treatments for CAA.
• Research involving people:
  • Brain donation studies look at the brains of individuals with CAA after they have died. This allows a detailed examination of exactly where CAA has developed, what abnormalities found on brain scans look like under the microscope, and it can provide information on the processes that lead to CAA.
  • Observational studies are clinical studies where there is no treatment offered as part of the study. Examples include biomarker studies, which are looking for new measures of CAA that might be early markers of disease, or measures associated with particular patterns of disease. Individuals with CAA involved in studies like this might have blood tests, brain scans and other tests to look for these new markers.
  • Treatment trials are clinical studies (sometimes called clinical trials) in which potential treatments for CAA are tested.

The best starting point is finding a neurologist with expertise in CAA, who will be able to advise on research studies that are active in your area. Please scroll to the bottom of this page for an interactive map to identify a neurologist with expertise in CAA in your geographical area.

Please see the answer to question nr. 5 ‘How do you treat CAA?’. The main strategies are good blood pressure control and avoidance of medications that increase the risk of bleeding, where possible.

Glossary of commonly encountered abbreviations and terms:

• Amyloid – a type of protein which tends to clump together, forming deposits
• Amyloid spells – also called transient focal neurological episodes, which can be a symptom of CAA
• Alzheimer’s disease – the most common type of dementia, caused by the same amyloid protein that causes CAA
• CAA – cerebral amyloid angiopathy, which is characterized by a build-up of the amyloid protein within the walls of blood vessels in the brain
• CMBs – cerebral microbleeds, which are small often non-symptomatic hemorrhages that are visible on a brain scan in individuals with CAA
• Cognitive impairment – difficulties with thinking and memory processes
• cSS – cortical superficial siderosis, which is the chronic manifestation of cSAH (see below)
• cSAH – convexity subarachnoid haemorrhage, which is bleeding on the surface of the brain
• Dementia – a progressive condition in which people might have difficulties with memory, thinking, language, and behavior
• ICH – intracerebral hemorrhage, which is symptomatic bleeding within the brain
• Seizure – these are caused by uncontrolled electrical activity in the brain, and can occur after part of the brain is damaged following a stroke. There can be many different symptoms, including shaking of one part or all of the body, loss of awareness and confusion
• Stroke – this is when the blood supply to the brain is faulty, resulting to damage in the part of the brain affected. Strokes can be due to clots (where the blood supply is blocked) or bleeding (where the blood supply leaks and blood then cannot reach its destination)
• TFNEs – transient focal neurological episodes, also called amyloid spells, which can be a symptom of CAA
• Vascular dementia – dementia caused by damage to blood vessels, which can include damage to larger blood vessels (as seen in post-stroke dementia) and small vessels (including vascular dementia associated with CAA)

For more information, visit the following websites.

Sporadic CAA: https://www.angiopathy.org/ and https://www.caacure.com/

Dutch-type CAA (formerly known as HCHWA-D):  https://www.hchwa-d.nl/en/ and https://dutchcaafoundation.nl/en/caa/

Alzheimer’s Association: https://www.alz.org/

American Heart Association: https://www.heart.org/

European Stroke Organization: http://www.eso-stroke.org/