In atherosclerosis, fats, cholesterol, platelets and white blood cells can build up and form plaques in the arteries. Diseases that have plaques in the brain involve an accumulation of beta-amyloid proteins, which are formed through an abnormal process, or involve prion proteins that attach to cells within the brain. The plaques can also form as part of an autoimmune process that attacks the body instead of foreign substances.
Alzheimer's Disease
Alzheimer's disease is the No. 1 cause of dementia throughout the world. There is an estimated 10 to 20 million people affected, according to Dr. Roger Simon, director of neurobiology research at Legacy Health Systems. The disease affects men as much as it affects women. Simon writes that scientists do not yet know what causes the disorder but that they have determined that genetic factors are responsible for approximately 5 percent of cases. Some families have a gene mutation, while people with Down syndrome are at a high risk of developing Alzheimer's when they are in their 40s. In Alzheimer's, people have plaques primarily made of a protein called beta-amyloid. Normally, a protein called APP is broken down and secreted out of the brain. The APP protein in those with Alzheimer's is not broken down correctly. This results in the beta-amyloid protein, which then accumulates.
Multiple Sclerosis
Scientists do not know what causes multiple sclerosis. One hypothesis is that when people get a virus infection, the virus does not leave the body but becomes dormant. Something then triggers that virus to become active, and an immune response starts, says Dr. Brian Apatoff, director of the Multiple Sclerosis Clinical Care and Research Center. Others hypothesize that it may be due to an autoimmune process, where the immune system attacks its own tissues and organs instead of only attacking foreign substances. The plaques in this disease involve macrophages, T cells and auto-antibodies. Macrophages and T cells are white blood cells. The auto-antibodies attack a substance that the nerves use to send fast signals. Whatever the cause, women have multiple sclerosis three times more often than men, according to Dr. Stephen Hauser, chairman of the Department of Neurology at the University of California.
Prion Disease
Prions are proteins that can attach to cells in the brain to cause rare but fatal diseases. The prion diseases include the "mad cow" disease that is found in cattle, scrapie which affects sheep, as well as Creutzfeldt-Jakob and the hereditary Gerstmann-Straussler-Scheinker syndrome, which infects humans. These diseases are also called transmissible spongiform encephalopathy because they create lesions in the brain that look like sponges. A group of scientists in the National Institute of Allergy and Infectious Diseases working jointly with scientists in the Veterinary Laboratories Agency of Scotland discovered through their research with mice that prion proteins can also cause plaques around the blood vessels in the brain.
References
- "Clinical Neurology"; Roger Simon, M.D., David Greenberg, M.D., Ph.D., Michael Aminoff, M.D.; 2009
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- Merck Manual for Healthcare Professionals: Multiple Sclerosis
- National Institutes of Health: Prion Found to Damage Brain Arteries
