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Amnesia is a condition in which memory is lost either by physical injury to the brain, disease, substance abuse, traumatic experience or by ingestion of toxic substances. People who suffer from amnesia are unable to recall information that is stored in memory. Memory loss can be temporary (transient global amnesia) or permanent.

Types of Amnesia

  • Retrograde: for events before the cause
  • Anterograde: inability to store new memories after the cause
  • Global: for information related to all senses and past times
  • Sense-specific: for events processed by one sense

Amnesia may be

  • Transient (as occurs after brain trauma)
  • Fixed (as occurs after a serious event such as encephalitis, global ischemia, or cardiac arrest), or
  • Progressive (as occurs with degenerative dementias, such as Alzheimer's disease).

Memory deficits more commonly involve facts (declarative memory) and, less commonly, skills (procedural memory).

Signs and Symptoms of Amnesia

Amnesia leads to loss or impaired ability to learn new information that is common in anterograde amnesia. It can also lead to loss of ability to recall past events in life or process familiar experiences or events, as in retrograde amnesia.

In some cases, one may not be able to transfer their short-term memory to their long-term memory. At times, old or deep memories from the childhood are retained and newer memories are lost. Isolated memory loss can cause loss of certain skill like inability to understand certain words or inability to read. Some may suddenly be able to learn a new skill like playing a guitar.

Person suffering from amnesia may have neurological problems like tremors or seizures. Some may develop false memories of events that never occurred. In some cases, the person is disoriented or confused.

Causes of Amnesia

There are many ways that can cause a person to lose memory.  When the limbic system is damaged, it could cause problems with memories. The limbic system consists of the thalamus and the hioppocampal formations. There are three causes of amnesia. These include head trauma, physical deficiencies and witnessing traumatic events. However, majority of the cases are due to head injuries and traumatic events. 

Some of the causes include:

  • Severe head injury
  • High fever
  • Seizures
  • Emotional shock
  • Alzheimer’s disease
  • Encephalitis
  • Deprivation of oxygen to the brain due to carbon monoxide poisoning, respiratory distress, heart attack, etc.
  • Subarachnoid hemorrhage
  • Brain tumor in the thalamus
  • Brain inflammation due to an infection such as herpes simplex virus
  • An autoimmune reaction to cancer cells present elsewhere in the body (paraneoplastic limbic encephalitis)
  • Electroconvulsive therapy
  • Head injuries due to car accidents
  • Wernicke-Korsakoff syndrome (vitamin B1 deficiency) due to long-term alcohol abuse
  • Use of certain medications such as benzodiazepines or illegal drugs

Traumatic events that trigger memory loss include:

  • Child abuse that includes sexual, physical, emotional abuse
  • Sexual abuse
  • Witness to a natural or man-made disaster
  • Witness to a very violent crime
  • Any situation that causes severe psychological stress and conflict

Diagnosis for Amnesia

The first step in diagnosis of amnesia is ruling out diseases that can lead to memory loss such as dementia, Alzheimer’s, brain tumor, etc. A physical examination will be conducted that includes reflexes, sensory function, balance, etc. The patient’s judgement, short and long term memory will be analyzed. The doctor will conduct a blood test to reveal any infection or deficiency that hampers memory function. Certain tests such as a MRI scan, CT scan as well as EEG will be conducted.

What are the treatment options available for Amnesia

Treatment focuses on techniques and strategies to help make up for the memory problem.

A person with amnesia may work with an occupational therapist to learn new information to replace what was lost, or to use intact memories as a basis for taking in new information.

Memory training may also include a variety of strategies for organizing information so that it's easier to remember and for improving understanding of extended conversation.

Many people with amnesia find it helpful to use a personal digital assistant (PDA). With some training and practice, even people with severe amnesia can use these electronic organizers to help with day-to-day tasks. Low-tech memory aids include notebooks, wall calendars, pill minders and photographs of people and places.

No medications are currently available for treating most types of amnesic syndrome.

Because Wernicke-Korsakoff syndrome involves a lack of thiamin, treatment includes replacing this vitamin and providing proper nutrition.

Researchers are investigating several neurotransmitters involved in memory formation, which may one day lead to new treatments for memory disorders.

The complexity of the brain processes involved makes it unlikely that a single medication will be able to resolve memory problems.

When to seek medical advice

  • Anyone who experiences unexplained memory loss, a head injury, confusion or disorientation requires immediate medical attention.
  • A person with amnesia may not be able to identify his or her location or have the presence of mind to seek medical care. If someone you know has symptoms of amnesia, don't hesitate to help the person get medical attention.

Support for amnesia

It is very traumatic and frustrating for people with amnesia to live a normal life. One may not remember family, friends as well as events that occurred in their life. Thus, it is very important for friends, family and other acquaintances extend full support to the affected person. One could join a support group to get help and advice related to living with amnesia.

Amnesia can cause many problems with personal life as well as result in loss of job. One needs to be patient and follow the advice of their doctor.