What is amnesia?

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People with amnesia also find it hard to remember the past, memorize new information, and imagine the future. This is because we construct future scenarios on the basis of our recollections of past experiences.

Our ability to recollect events and experiences involves a variety of complex brain processes. We still don’t understand exactly what happens when we commit something to memory, or when we try to retrieve data stored in our brain.

Most people with amnesia are usually lucid and have a sense of self. However, they may experience severe difficulties in learning new information, struggle to recall memories of past experiences, or both.

Types

• Anterograde amnesia: The person cannot remember new information. Things that happened recently and information that should be stored into short-term memory disappear. This usually results from a brain trauma, when a blow to the head causes brain damage, for example. The person will remember data and events that happened before the injury.
• Retrograde amnesia: In some ways the opposite of anterograde amnesia, the person cannot remember events that occurred before their trauma, but they remember what happened after it. Rarely, both retrograde and anterograde amnesia can occur together.
• Transient global amnesia: A temporary loss of all memory and, in severe cases, difficulty forming new memories. This is very rare and more likely in older adults with vascular (blood vessel) disease.
• Traumatic amnesia: Memory loss results from a hard blow to the head, for instance, in a car accident. The person may experience a brief loss of consciousness or a coma. The amnesia is usually temporary, but how long it lasts normally depends on how severe the injury is. Amnesia can be an important indicator of concussion.
• Wernicke-Korsakoff’s psychosis: Extended alcohol abuse can lead to progressive memory loss that worsens over time. The person may also have neurological problems, such as poor coordination and a loss of feeling in the toes and fingers. It can also be caused by malnutrition, specifically a thiamin (vitamin B1) deficiency.
• Hysterical (fugue or dissociative) amnesia: Rarely, a person can forget not only their past but also their identity. They may wake up and suddenly have no sense of who they are. Even if they look in the mirror, they do not recognize their own reflection. A driving license, credit cards, or ID card will be meaningless. It is usually triggered by an event that the person’s mind is unable to cope with properly. The ability to remember usually returns either slowly or suddenly within a few days, but the memory of the shocking event may never come back completely.
• Childhood amnesia (infantile amnesia): The person cannot recall events from early childhood, possible because of a language development problem or some memory areas of the brain not fully maturing during childhood.
• Posthypnotic amnesia: Events during hypnosis cannot be recalled.
• Source amnesia: The person can remember certain information but not how or where they got that information.
• Blackout phenomenon: A bout of heavy drinking can leave a person with memory gaps, where they cannot remember chunks of time during the binge.
• Prosopamnesia: The person cannot remember faces. People can either acquire it or be born with it.

• The ability to learn new information is impaired in anterograde amnesia.
• The ability to remember past events and previously familiar information is impaired in retrograde amnesia
• False memories may be either completely invented or consist of real memories misplaced in time, in a phenomenon known as confabulation.
• Uncoordinated movements and tremors indicate neurological problems.
• Confusion or disorientation may occur.
• There may be problems with short-term memory, partial or total loss of memory
• The person may be unable to recognize faces or locations.

Amnesia is different from dementia. Dementia includes memory loss, but it also involves other important cognitive problems that may affect the patient’s ability to carry out daily activities.

Causes

Damage to brain structures that form the limbic system, such as the hippocampus and thalamus, can lead to amnesia – the limbic system controls our emotions and memories.

Medical amnesia

Amnesia resulting from brain injury or damage.

Possible causes are:

• Stroke
• Encephalitis, or brain inflammation, due to a bacterial or viral infection or an autoimmune reaction
• Celiac disease may be linked to amnesia, confusion, and personality changes
• Oxygen deprivation, resulting, for example, from a heart attack, respiratory distress, or carbon monoxide poisoning
• Some medications, such as the sleeping drug, Ambien
• Subarachnoid hemorrhage, or bleeding in the area between the skull and the brain
• A brain tumor that affects a part of the brain involved in memory
• Some seizure disorders
• Electroconvulsive therapy (ECT)), or electroshock therapy, a psychiatric treatment where seizures are induced for therapeutic effect, may lead to temporary memory loss
• Head injuries, which can lead to loss of memory that is usually temporary

Psychological amnesia

Also known as dissociative amnesia, this is caused by an emotional shock, such as:

• a violent crime
• sexual or other abuse
• military combat
• a natural disaster
• a terrorist act

Any intolerable life situation that causes severe psychological stress and internal conflict can lead to some degree of amnesia. Psychological stressors are more likely to disrupt personal, historical memories rather than interfere with laying down new memories.

Diagnosis

They will take a detailed medical history, which may be difficult if the patient does not remember. Family members or caregivers may need to be present.

The doctor will need the patient’s permission to talk about their medical details with somebody else.

Questions can include:

• Can the patient remember recent events and events further back in time?
• When did the memory problems start?
• How did they develop?
• Could any factors have caused the memory loss, such as a head injury, surgery, or stroke?
• Is there a family history of any neurological or psychiatric conditions?
• Does the person consume alcohol?
• Are they using any medication?
• Have they taken illegal drugs, such as cocaine or heroin?
• Are the symptoms undermining their ability to look after themselves?
• Do they have a history of depression or seizures?
• Have they ever had cancer?

A physical exam might include checking aspects of the brain and nervous system, such as:

• reflexes
• sensory function
• balance

The doctor may also check the patient’s:

• judgment
• short-term memory
• long-term memory

The memory assessment will help determine the extent of memory loss. This will help find the best treatment.

To find out whether there is any physical damage or brain abnormality, the doctor may order and MRI or CAT scan, or an electroencephalogram (EEG).

Blood tests may reveal the presence of any infection or nutritional deficiencies.

Treatment

Psychotherapy can help some patients. Hypnosis can be an effective way of recalling memories that have been forgotten.

Family support is crucial. Photographs, smells, and music may help.

Treatment often involves techniques and strategies to help compensate for the memory problem.

This may involve:

• Working with an occupational therapist to acquire new information to replace lost memories, or to use existing memories as a basis for acquiring new information.
• Learning strategies for organizing information, to make it easier to store.
• Using digital aids, such as smartphones, to help with daily tasks and remind patients about important events, when to take medications, and so on. A contact list with photographs of faces may be helpful.

There are currently no drugs for restoring memory lost due to amnesia.

Malnutrition or Wernicke-Korsakoff syndrome can involve memory loss due to a thiamin (vitamin B1) deficiency, so targeted nutrition can help.

Whole grain cereals, legumes (beans and lentils), nuts, lean pork, and yeast are rich sources of thiamin.