Amnesia means a temporary or permanent loss of memory. Amnesia can be caused by brain trauma or physical damage to the brain from wounds, tumors, viruses, or lesions; degenerative brain diseases such as Alzheimer’s disease; seizures; certain drugs or alcohol; and by mental disorders such as post-traumatic stress. Amnesia that is the result of psychological factors is called psychogenic amnesia. Most episodes of amnesia last a few seconds to a few hours, but in rare cases, amnesia can last for months or even years. The worst case of amnesia ever recorded was that of British musician Clive Wearing, whose brain was damaged from a bout of encephalitis virus in 1985. Since that time, he cannot form memories that last longer than seven to 30 seconds.
Amnesia can take away different forms of memories. The ability to remember things that just happened a few minutes ago or “short term memory” is most often affected. People with this kind of amnesia can retain “long-term memories” of their childhoods and adolescence and yet be unable to remember things that happened a few minutes ago. “Procedural” memories involve habits and abilities, such as playing the piano or riding a bicycle. Amnesiacs can usually retain procedural memories more than “declarative memory,” which is the ability to remember facts.
When you visit a physician because of amnesia, you will usually undergo various tests, such as magnetic resonance imaging and an electroencephalogram, in order to determine the organic basis of the problem. If you have a brain tumor or other organic disease, your doctor will treat that condition. There is no known drug or cure for amnesia, although many patients improve through memory training and using high-tech devices such as Blackberries or low-tech ones like calendars to help them remember appointments and so forth.
Age-associated memory loss is not amnesia, but rather the natural degradation of memory function that occurs as people grow older.