Senile plaques are deposits of protein that form outside the brain cells. The protein clumps distinctively and can be clearly seen on a microscopic examination of a sample from a patient. Senile plaques, along with tangles, are two key diagnostic findings in people with Alzheimer's disease and they can also be observed in some other degenerative neurological conditions. They are commonly uncovered on autopsies of older adults and the risk of having plaques increases significantly after age 60, especially among women.
The protein that forms senile plaques is known as amyloid-beta (a-beta) protein. The plaques are also referred to as amyloids. Amyloids can form elsewhere in the body as well, as seen in the condition amyloidosis. The protein is believed to have neurotoxic properties that contribute to cognitive degeneration. In addition, senile plaques can physically interfere with the conduction of signals in the brain and may push brain tissue aside, disrupting normal brain function in the patient.
Plaques have been noted in brain tissue since the late 1800s, and researchers began connecting them with cognitive decline in the 20th century. Researchers working on conditions like Alzheimer's realized that all patients shared traits like the presence of plaques and tangles in the brain, as noted in autopsies of patients after they died. Senile plaques can also be identified in brain biopsies, although because biopsies are invasive, they are not usually recommended. Patients who appear to be developing symptoms of senility will be treated for senility without biopsied.
Understanding how senile plaques form can help researchers develop approaches to treatment of people with conditions like Alzheimer's. In addition to working on pharmaceuticals that could slow, stop, or regress plaque formation, researchers are also interested in finding ways to prevent the development of plaques in the first place. Numerous facilities around the world are studying the development of senility and ways that it can be addressed, as improvements in medical care have increased life expectancy and subsequently increased the chances that people will live long enough to develop cognitive degeneration.
In patients with senile plaques, brain function is gradually eroded as the plaques form and spread. Depending on the location of the plaques, different types of cognitive function may be impaired. Patients can lose their memories, have difficulty speaking, and develop physical symptoms like tremors and an unsteady gait. Senile plaques can also contribute to the development of mood changes like aggression and depression in older adults.