Amnesia
What is amnesia?
Amnesia means loss of memory. The temporary inability to put a name to a familiar face is something we all experience. Once we remember the name it is hard to understand how we forgot it.
Strictly speaking amnesia really means loss of certain memories, rather than a general loss of the ability to remember anything — something that is much rarer. The process of memory is complex and not fully understood. It seems that different areas of the brain are involved in different types of memory — which is really an information storage system rather like a filing cabinet or computer.
What causes amnesia?
Many things can cause episodes of amnesia. These include infections and injuries to the brain, drugs, epilepsy, stroke and reduced blood circulation, particularly in older people.
In dementia, most often seen as Alzheimer’s disease, recent memories are lost first, while the memory of things in the distant past often remains crystal clear.
The brain is one of the busiest organs. Although the brain represents only 2 per cent of our body weight, it takes 15 per cent of the body’s blood supply, uses 25 per cent of the body’s oxygen and uses 70 per cent of our energy-producing glucose.
What is transient global amnesia?
An alarming but non-serious form of temporary amnesia is known as transient global amnesia (TGA). Affected people are usually middle-aged or elderly. They appear quite normal, know who and where they are, recognise people around them and can function quite normally in activities such as driving a car. However, they have a profound loss of recent memory, usually for a period of 4 to 8 hours, but sometimes up to 24 hours. Understandably this is a very frightening experience, both for the affected person and those around them.
Symptoms of transient global amnesia
People with transient global amnesia will usually keep repeating questions and appear anxious, agitated and perplexed. And they will be fully aware that there is an inexplicable blank period in their memory.
Causes and recovery of transient global amnesia
We do not know why transient global amnesia happens. Sometimes it follows severe pain, extreme physical activity, accidents or strong emotional experiences. Having had an episode of transient global amnesia does not mean that a stroke becomes more likely, or that the person is suffering from any other physical problem. Recovery is usually very rapid and complete. About one in 5 people who have experienced TGA will have a second attack. Very rarely, they will have a third.
What to do if you or someone else has sudden memory loss
Because there’s no easy way to tell transient global amnesia from potentially life-threatening conditions that can cause sudden memory loss, seek immediate medical attention if you or someone you know has sudden memory loss.
Last Reviewed: 06 December 2007
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