In simple terms Amnesia means loss of memory. When a person does not recollect data stored in his mind, it is known as Amnesia. Normally it is natural for a person to remember the past and act accordingly in future, on the basis of his past experience. Amnesia also refers to debility to recall information stored in the memory. People with Amnesia usually find it hard to think about the future since most of the times it is human nature to act on past references, but here it becomes difficult. For example if a person had a bad accident while horse riding then he or she would be extra careful the next time but not so in case of Amnesia. So to say, any important piece of information which a person will not usually forget and which is forgotten is ‘Amnesia’. 

The most likely cause of Amnesia is from within i.e. Organic or Natural, and other is Functional cause. 

Organic Causes: Includes Injury to the head that results in brain damage. Other causes may be some disease like Alzheimer’s and in some cases the use of certain drugs, especially sedative drugs which induce sleep.

Functional Causes: Are of psychological nature where a person resorts to defence mechanism and tends to forget things which he does not want to remember.

Amnesia is a general condition and may affect both men and women alike and is not fatal and not infectious or contagious.

Usually it is human nature to store information in the brain and reproduce it whenever it is required; say a group of friends go on a school picnic and enjoy the same, but after many long years when one of them has difficulty recollecting the moments which are of particular importance then it is ‘disturbing’. Such disturbance in the stored information may be of any duration, say of minutes or hours or months, and which is normally not forgotten. In simple terms Amnesia can be explained as the loss of memory.

The different types of Amnesia are:

Anterograde amnesia - the patient does not remember recent things. That is, no short term memory.  Caused by an injury to the head (trauma). However, the patient will remember data and events prior to the injury.

Retrograde Amnesia – Contrary to Anterograde Amnesia, the patient will not remember data and events prior to his trauma/injury but remember everything after that.

Transient global Amnesia - a temporary total memory loss. A patient with this type of Amnesia also finds it difficult to form new memories - they have severe Anterograde Amnesia. The loss of past memories is milder. This mostly affects older people who have a vascular disease (a problem with the blood vessels).

Traumatic Amnesia - memory loss which is caused by a hard blow to the head followed by a brief loss of consciousness or even goes into a coma. The amnesia could be temporary or permanent- how long it lasts usually depends on how severe the injury is.

Wernike-Korsakoff's psychosis - extended alcohol abuse causes this type of memory loss. It progressively gets worse with time. It is linked to thiamin deficiency.

Hysterical (fugue) Amnesia – This is a rare type wherein patients forget their very identity. The onset could be sudden and is usually triggered by an event that the person's mind is unable to cope with properly. The memory may return eventually, either slowly or suddenly, but not completely.

Childhood Amnesia (infantile amnesia) - events from early childhood are not recalled. Some say it is possible that some memory areas of the brain were not fully mature during childhood while some experts maintain it is due to language deficiencies.

Posthypnotic amnesia - events that transpired under hypnosis cannot be recalled.

Source Amnesia – when you can remember the information but not the source where you got it from.

Blackout phenomenon – When a person cannot recollect chunks of time; normally after a heavy binge of alcohol abuse.

Prosopamnesia – when patients cannot remember faces. This sort of Amnesia is from birth or contracted later.

Amnesia is diagnosed by the following techniques:

Firstly the doctor will have to determine whether the condition is Amnesia or any other form of memory loss like those associated with Alzheimer’s disease, brain tumour or depression. The tests for Amnesia include:
 

• A detailed Medical history is compiled which includes interviews with the patient and close family members to evaluate the extent of memory loss.
• Any head injury, stroke or surgery.
• Drug abuse or Alcohol intake.
• Family history with neurological problems.
• Any other factors like depression, fits and seizures, headaches, confusion, language problems, any other underlying condition.
• Certain physical tests to check reflexes and balance
• Imaging Tests like MRI and CT SCAN to check for any damage to the brain.
• Blood tests to check for nutrient deficiencies.

Amnesia in itself is not fatal or life threatening. But if there are other underlying conditions like Alzheimer’s in case of Organic Amnesia due to which there is progressive deterioration of the nerve cells thereby affecting the physical and mental capabilities of a person then it may prove fatal in terms of memory loss and eventually death.

Hypnosis and Psychotherapy help in cases of certain Amnesia and the person can regain most of the lost memory and in this process, with the help of family members and professional help the patient recovers to a large extent.

Exposing the person to familiar surrounding and events may bring back some of the lost memory in case of functional Amnesia.

Amnesia involves memory loss hence a person affected with Amnesia does not recall about a particular event which may have caused an injury to the brain thus leading to memory loss and may tend to repeat the same event thereby causing further injury. To prevent this complication use of Alcohol is to be prohibited.

Treatment of any infection should be quick so that it does not spread to the brain.

It is advisable to seek immediate medical help if there are symptoms which may cause stroke or heart attack, severe headache, or in case of paralysis.

Healthy lifestyle, Nutrition, Exercising and protective gear while driving and restricting use of alcohol and intoxicating substances go a long way to a healthy life and restrict spread and delay of certain conditions.

Henry Gustav Molaison is one of the most famous cases of Amnesia. Henry Gustav Molaison better known as H.M. was born on 26 February 1926 in the US. Henry suffered from Epilepsy and a surgery was done to remove parts of his brain to cure epilepsy. This epilepsy could have been the result of a bicycle accident that he suffered at the age of 7 and consequently suffered from fits and seizures.

In the year 1953 a successful surgery was performed on his brain to cure epilepsy. But Henry became a Retrograde Amnesic. He could not remember events before the surgery but could easily learn new skills.

Henry could easily solve crossword puzzles and could recall certain events before 1953 and was able to modify new information after the year 1953 and in fact his was a case of both long term and short term memory loss. His case played a very important role in the study of brain functions and memory. He stayed in a care institute and was a subject of investigation. And in this period he possessed certain intellectual capabilities.

Henry died in the year 2008 at the age of 82 and his brain is now preserved at UC San Diego where it was sliced for histological purposes.