Amnesia

What is amnesia?

Amnesia is a term used to cover the partial or complete loss of memory. It is most often a temporary condition and covers only a part of a person's experience, such as immediate memory (for example, complete loss of all memories, especially from childhood or long ago, is very unusual).

Amnesia - causes and risk factors

Common causes include:

• Acute events (such as a stroke or seizure) or traumatic accident (typically a head injury) that may or may not lead to permanent damage to the brain.
• Damage to the brain from chronic poisoning, most often from excessive alcohol intake.
• The decline in brain function linked to dementia in conditions such as Alzheimer’s disease or Lewy Body disease.
• Psychological factors including stress and anxiety.

In all these conditions there is either physical damage to the nerve tissue of the brain, disruption of chemical nerve signal transmission or an overriding psychological influence.

So many other symptoms are also often present and can be a clue to the cause of amnesia, including:

• Altered consciousness.
• Disruption of general intellectual performance.
• Judgement and problem solving.
• Abnormal behaviour or emotions.
• Problems with muscle movement or strength.

The main types of amnesia are:

• Anterograde amnesia. People who find it hard to remember ongoing events after suffering damage to the head. They do not tend to forget their childhood, who they are, or things they learned prior to an accident, but have trouble remembering day-to-day events. This makes it difficult to manage a simple routine, as they forget where they are supposed to be or what they are supposed to be doing, or to follow any activity where a sequence of actions is needed.
• Retrograde amnesia. People who find it hard to retrieve memories prior to an incident in which they suffer damage to the head. Sometimes people never remember the seconds leading up to the incident, while in other cases whole days or weeks can be lost.
• Korsakoff's psychosis. Memory loss caused by alcohol abuse. The person's short-term memory may appear normal, but they will have severe problems recalling a simple story, lists of unrelated words, faces and complex patterns. ‘Confabulation’, where sufferers make up stories to fill the gaps in their memory is typical of this type of amnesia. This tends to be a progressive disorder and is usually accompanied by neurological problems, such as uncoordinated movements and loss of feeling in the fingers and toes. Even after five years of abstinence from alcohol, memory can still be affected.
• Traumatic amnesia. This follows brain damage caused by a severe non-penetrative blow to the head, such as in a road accident. Such trauma can lead to anything from a loss of consciousness for a few seconds to coma, and may result in memory gaps from minutes to weeks.
• Infantile/childhood amnesia. This refers to a person's inability to recall events from early childhood. There are many theories on this and several blame intense psychological stress - for example, Freud put it down to sexual repression but modern research has disputed the existence of such ‘buried memories’.
• Transient global amnesia. This covers episodes of amnesia mostly linked to psychological trauma but sometimes following a medical procedure or vigorous exercise. Typically, it causes repetitive questioning and sometimes confusion but the person knows who they are. It lasts for 4-12 hours with a full recovery. If there is a loss of personal identity, then this is known as a fugue amnesia and is due to severe psychological trauma. Usually, the memory comes back slowly or suddenly a few days later, although memory of the trauma may remain incomplete.

Amnesia treatment and management

Treatment varies according to the type of amnesia and the suspected cause. Anyone suffering any symptoms of amnesia should seek medical attention. Further tests and investigations (such as brain scans) may be urgently needed to check for problems such as damage to the brain from trauma or haemorrhage, or disruption of other systems in the body.

Amnesia may improve with time or effective treatment of an underlying condition. But many affected people have to live with some long term disruption of their memory, and specialist help and support may be needed to enable them to cope with day to day living.