What is it?

Though having no sense of who you are is a common plot device in movies and television, real-life amnesia generally doesn't cause a loss of self-identity.

Instead, people with amnesia — also called amnestic syndrome — are usually lucid and know who they are, but may have trouble learning new information and forming new memories.

Amnesia can be caused by damage to areas of the brain that are vital for memory processing. Unlike a temporary episode of memory loss (transient global amnesia), amnestic syndrome can be permanent.

There's no specific treatment for amnesia, but techniques for enhancing memory and psychological support can help people with amnesia and their families cope.

Symptoms

The two main features of amnesia are:

• Impaired ability to learn new information following the onset of amnesia (anterograde amnesia)
• Impaired ability to recall past events and previously familiar information (retrograde amnesia)

Most people with amnestic syndrome have problems with short-term memory — they can't retain new information. Many also have some degree of impaired memory recall. Recent memories are most likely to be lost, while more remote or deeply ingrained memories may be spared. Someone may recall experiences from childhood or know the names of past presidents, but not be able to name the current president or remember what month it is or what was for breakfast.

The memory loss doesn't affect a person's intelligence, general knowledge, awareness, attention span, judgment, personality or identity. People with amnestic syndrome usually can understand written and spoken words and can learn skills such as bike riding or piano playing. They may also understand that they have a memory disorder.

Amnesia isn't the same as dementia. Dementia often includes memory loss, but it also involves other significant cognitive problems that lead to a decline in the ability to carry out daily activities. A pattern of forgetfulness is also a common symptom of mild cognitive impairment (MCI), but the memory and other cognitive problems in MCI aren't as severe as those experienced in dementia.

Additional signs and symptoms

Depending on the cause of the amnesia, other signs and symptoms may include:

• False recollections, either completely invented or made up of genuine memories misplaced in time
• Neurological problems such as uncoordinated movements, tremors or seizures
• Confusion or disorientation

Causes

Normal memory function involves many parts of the brain, and any disease or injury that affects the brain can interfere with the intricacies of memory. Amnesia can result from damage to brain structures that form the limbic system, which controls your emotions and memories. These structures include the thalamus, which lies deep within the center of your brain, and the hippocampal formations, which are located within the temporal lobes of your brain.

An amnestic syndrome caused by brain injury or damage is known as neurological or organic amnesia. Possible causes of neurological amnesia include:

• Stroke
• Brain inflammation (encephalitis) resulting from infection with a virus such as herpes simplex virus (HSV) or as an autoimmune reaction to cancer somewhere else in the body (paraneoplastic limbic encephalitis)
• Lack of adequate oxygen in the brain (for example, from heart attack, respiratory distress ) Long-term alcohol abuse leading to thiamin (vitamin B-1) deficiency (Wernicke-Korsakoff syndrome)
• Tumors in areas of the brain that control memory
• Degenerative brain diseases, such as Alzheimer's disease and other forms of dementia

Head injuries, such as those sustained in car accidents, can lead to confusion and problems remembering new information, especially in the early stages of recovery — but usually don't cause severe amnesia.

Another rare type of amnesia, called psychogenic or dissociative amnesia, stems from emotional shock or trauma, such as being the victim of a violent crime. In this disorder, a person may lose personal memories and autobiographical information, usually for just a brief time.

Risk factors

The chance of developing amnesia might increase if you've experienced:

• Brain surgery, head injury or trauma
• Stroke
• Alcohol abuse
• Seizures

How is Amnesia Diagnosed?

To diagnose amnesia, a doctor will do a comprehensive evaluation to rule out other possible causes of memory loss, such as Alzheimer's disease, dementia, depression or brain tumor.

Medical history

The evaluation starts with a detailed medical history. Because the person with memory loss may not be able to provide thorough information, a family member, friend or another caregiver generally takes part in the interview as well.

The doctor will ask many questions to understand the memory loss. Issues that might be addressed include:

• Type of memory loss (can the person remember recent events and remote events?)
• When the memory problems started and how they progressed
• Triggering factors, such as head injury, stroke or surgery
• Family history, especially of neurological disease
• Drug and alcohol use
• Other signs and symptoms, such as confusion, language problems, personality changes or impaired ability to care for self
• History of seizures, headaches, depression or cancer

Physical exam

The physical examination may include a neurological exam to check reflexes, sensory function, balance and other physiological aspects of the brain and nervous system.

Cognitive tests

The doctor will test the person's thinking, judgment, and recent and long-term memory. He or she will check the person's knowledge of general information — such as the name of the current president — as well as personal information and past events. The memory evaluation can help determine the extent of memory loss and provide insights about what kind of help the person may need.

Imaging tests

Diagnostic imaging tests — including magnetic resonance imaging (MRI), computerized tomography (CT) and electroencephalogram (EEG) — may be ordered to look for damage or abnormalities in the brain. Blood tests can check for infection, nutritional deficiencies or other issues.

How do you treat Amnesia?

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

Occupational therapy

• 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.

Technological assistance

• Many people with amnesia find it helpful to use a personal digital assistant (PDA), such as a BlackBerry or iPhone. With some training and practice, even people with severe amnesia can use these electronic organizers to help with day-to-day tasks. For example, they can program the PDA to remind them about important events or to take medications.
• Low-tech memory aids include notebooks, wall calendars, pill minders and photographs of people and places.

Medications or supplements

• No medications are currently available for treating most types of amnestic syndrome. Because Wernicke-Korsakoff syndrome involves a lack of thiamin, treatment includes replacing this vitamin and providing proper nutrition. Although treatment, which also needs to include alcohol abstinence, can help prevent further damage, most people won't recover all of their lost memory.

How to live with Amnesia

• Living with amnesia can be very frustrating for the person with memory loss, and for their family and friends too. More-severe forms of amnesia may require direct assistance for the affected individual from family, friends or professional caregivers.
• It can be helpful to talk with others who understand what you're going through, and who may be able to provide advice or tips on living with amnesia. Ask your doctor if he or she knows of a support group in your area for people with amnesia and their loved ones.

Prevention

Because damage to the brain can be a root cause of amnesia, it's important to take steps to minimize your chance of a brain injury. For example:

• Avoid excessive alcohol use
• Wear a helmet when bicycling and a seat belt when driving
• Treat any infection quickly so that it doesn't have a chance to spread to the brain
• Seek immediate medical treatment if you have any symptoms that suggest a stroke or brain aneurysm, such as a severe headache or one-sided numbness or paralysis

References:

http://en.wikipedia.org/wiki/Amnesia
http://www.medicalnewstoday.com/articles/9673.php
http://www.mayoclinic.org/diseases-conditions/amnesia/basics/definition/con-20033182
http://www.irishhealth.com/article.html?con=308