Cerebral Amyloid Angiopathy

Definition

Definition of Cerebral Amyloid Angiopathy
Cerebral amyloid angiopathy (CAA), also known as congophilic angiopathy, is a form of angiopathy in which amyloid deposits form in the walls of the blood vessels of the central nervous system. The term congophilic is used because the presence of the abnormal aggregations of amyloid can be demonstrated by microscopic examination of brain tissue after application of a special stain called Congo red. The amyloid material is only found in the brain and as such the disease is not related to other forms of amyloidosis.

Symptoms

Symptoms of Cerebral Amyloid Angiopathy
Cerebral amyloid angiopathy can cause bleeding into the brain, usually in the outer parts of the brain, called the lobes, and not the deep areas. Symptoms occur because bleeding in the brain harms brain tissue. If there is a lot of bleeding, immediate symptoms occur and resemble a stroke. Such symptoms include:

1. Drowsiness
2. Headache (usually in a specific part of the head)
3. Seizures
4. Stupor or coma (rarely)
5. Vomiting

Causes

Causes of Cerebral Amyloid Angiopathy
CAA has been identified as occurring either sporadically (generally in elderly populations) or in familial forms such as Flemish, Iowa, and Dutch types. Sporadic forms of CAA have been further characterized into two types based on deposition of amyloid ß-protein (Aß) in cortical capillaries. In all cases, it is defined by the deposition of Aß in the leptomeningal and cerebral vessel walls.

The reason for increased deposition of Aß in sporadic CAA is still unclear with both increased production of the peptide and abnormal clearance having been proposed as potential causes. Under normal physiology Aß is cleared from the brain by four pathways: (1) endocytosis by astrocytes and microglial cells, (2) enzymatic degradation by neprilysin or insulysin (3) cleared by way of the blood brain barrier or (4) drained along periarterial spaces. Abnormalities in each of these identified clearance pathways have been linked to CAA.

Diagnosis

Diagnosis of Cerebral Amyloid Angiopathy
Susceptibility weighted imaging has been proposed as a tool for identifying CAA-related microhemorrhages.

Presentation

Presentation of Cerebral Amyloid Angiopathy
Amyloid deposition predisposes these blood vessels to failure, increasing the risk of a hemorrhagic stroke. Since this can be caused by the same amyloid protein that is associated with Alzheimer's dementia such brain hemorrhages are more common in people who suffer from Alzheimer's, however they can also occur in those who have no history of dementia. The hemorrhage within the brain is usually confined to a particular lobe and this is slightly different compared to brain hemorrhages which occur as a consequence of high blood pressure (hypertension) - a more common cause of a hemorrhagic stroke (or cerebral hemorrhage).

Treatment

Treatment of Cerebral Amyloid Angiopathy
There is no known effective treatment. The goal of treatment is to relieve symptoms. In some cases, rehabilitation is needed for weakness or clumsiness. This can include physical, occupational, or speech therapy.

Occasionally, some patients may benefit from medications that help improve memory, such as those used to treat Alzheimer's disease.

Seizures, sometimes called “amyloid spells,” may be treated with anticonvulsants such as phenytoin (Dilantin) and carbamazepine (Tegretol).