Causes of Amnesia

A person who is a little forgetful in their day-to-day life does not have amnesia. Amnesia refers to a large-scale loss of long-term memory due to illness, brain injury, or psychological trauma.

Some people with amnesia have difficulty forming new memories. Others can’t recall facts or past experiences. People with amnesia usually retain knowledge of their own identity in addition to their motor skills.

Mild memory loss is a normal part of aging. Significant memory loss or the inability to form new memories may indicate the presence of an amnestic disorder.

A person’s ability to recall events and experiences involves a variety of complex brain processes. Researchers still do not understand exactly what happens when a person commits something to memory or retrieves information stored in the brain.

When a person develops amnesia, they often lose memories of important milestones, key events or people in their life, and vital facts they have learned.

Most people with amnesia are lucid and have a sense of self. In some cases, they may have full memories up to a certain point in time but have difficulty remembering things afterward. In other cases, they will lose memories from before a point in time. More often, the memory loss is patchy, with a person losing memories of certain events.

Some people with amnesia find it hard to imagine the future. This is because the human brain constructs future scenarios based on its recollections of past experiences.

Types of Amnesia

There are several different conditions involve amnesia, and there are many types of amnesia. Some features of different types of amnesia can overlap, and a person can have more than one type. Amnesia can be temporary or long lasting.

Following are the most common types of amnesia:

• Anterograde Amnesia: A person with anterograde amnesia cannot remember new information. This usually results from brain trauma, such as a blow to the head that causes brain damage. The person will have their full memory from the time before the injury.
• Retrograde Amnesia: In some ways the opposite of anterograde amnesia, retrograde amnesia is when a person cannot remember events that occurred before their trauma, but they can remember what happened after it. In rare cases, both retrograde and anterograde amnesia can occur together.
• Transient Global Amnesia: This is 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: This refers to memory loss resulting from a hard blow to the head, for instance, in a car accident. The person may experience a brief loss of consciousness or coma. This type of amnesia is usually temporary, but its duration often depends on the severity of the injury. Amnesia can be an important indicator of concussion.
• Fugue or Dissociative Amnesia: Rarely, a person can forget both their past and their identity. They may wake up and suddenly have no sense of who they are. The trigger is usually a traumatic event. The ability to remember commonly returns within minutes, hours, or days, but the memory of the triggering event may never come back completely.
• Posthypnotic amnesia: A person cannot recall what occurred while they experienced hypnosis.
• Source amnesia: A person can remember certain information but not how or where they got it.
• Alcohol-induced amnesia: Also called a blackout, this is when a bout of heavy drinking leaves a person with memory gaps.
• Prosopamnesia: The person cannot remember faces. People can either acquire it or be born with it.

Another type of amnesia is childhood amnesia, or infantile amnesia. However, this is not an actual disorder. A young child’s language and memory are still developing. As a result, most adults cannot recall events from early childhood.

Causes of Amnesia

Any disease or injury that affects the brain can interfere with memory. Memory function engages many different parts of the brain simultaneously.

Damage to brain structures that form the limbic system, such as the hippocampus and thalamus, can lead to amnesia. The limbic system controls a person’s emotions and memories.

Medical Causes

Amnesia may result from brain injury or damage. Possible causes include the following:

• A brain tumor that affects a part of the brain involved in memory.
• Certain medications, such as the insomnia drug Ambien
• Head injuries, which can lead to loss of memory that is usually temporary.
• Illnesses that cause encephalitis, or brain inflammation, which typically include bacterial or viral infection or autoimmune reaction.
• Oxygen deprivation, which may result from a heart attack, respiratory distress, or carbon monoxide poisoning.
• Some seizures disorder.
• Subarachnoid hemorrhage, or bleeding in the area between the skull and the brain
• Stroke
• Surgery and anesthesia, which may cause a person to have trouble remembering what happened right before or after the procedure.

Wernicke-Korsakoff syndrome, a condition caused by extended alcohol misuse or thiamin (vitamin B1) deficiency, can lead to progressive memory loss that worsens over time. It can also lead to neurological problems, such as poor coordination and loss of feeling in the toes and fingers.

Psychological Amnesia

Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM–5) lists amnesia as a type of dissociative disorder. This usually refers to anterograde or retrograde amnesia caused by psychological trauma or stress without the presence of any physical cause.

Examples of dissociative conditions that can present with amnesia include the following:

• Acute stress disorder
• Dissociative identity disorder
• Post-Traumatic Stress Disorder (PSTD)
• Dissociative fatigue

Contributing traumatic causes or triggers can include the following:

• Being sexually, physically, or emotionally abused
• Experiencing violent crime or a terrorist attack
• Going through a trauma while serving in the military
• Surviving a natural disaster

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 forming new memories.

Signs and Symptoms of Amnesia

The primary symptom of amnesia is memory loss or the inability to form new memories. If you have amnesia, you may experience the following:

• An impaired ability to learn new information (anterograde amnesia).
• Confusion
• Difficulty recalling facts, events, places, or specific details (which can range from what you ate this morning to the name of the current president). 
• Impaired ability to remember past events and previously familiar information (retrograde amnesia)
• An inability to recognize locations or faces. 
• Impaired short-term memory
• Confabulation, in which the brain subconsciously invents false memories to fill in memory gaps. 
• Experiencing false memories, which are either completely invented memories or real memories misplaced in time, a phenomenon known as confabulation.
• Partial or total loss of all memory

You’ll still retain your motor skills, such as your ability to walk, as well as fluency in any languages you speak.

Diagnosis of Amnesia

A doctor will need to rule out other possible types of memory loss, including those caused by dementia, Alzheimer’s disease, depression, or a brain tumor.

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

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

Questions may include:

• Are they taking any medication?
• Can the person remember recent events and events further back in time?
• Could any factors have caused the memory loss, such as a head injury, surgery, or stroke?
• Does the person consume alcohol?
• How did they develop?
• Is there a family history of any neurological or psychiatric conditions?
• 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? 
• When did the memory problems start?

The doctor will also do a physical exam that might include checking certain brain and nervous system functions, such as:

• Balance
• Reflexes
• Sensory function

The doctor may also check the patients:

• Judgment
• Long-term memory
• Short-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 an magnetic resonance imaging (MRI), computerized tomography (CT) scan or electroencephalogram (EEG).

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

Treatment of Amnesia

In many cases, amnesia resolves without treatment. However, if an underlying physical or mental disorder is present, treatment for that condition may be necessary.

Psychotherapy or cognitive behavioral therapy (CBT) may help some people with amnesia. Hypnosis can be an effective way of recalling forgotten memories. Working on retrieving memories and managing psychological issues that may have contributed to amnesia are important aspects of any amnesia treatment.

Meditation and related mindfulness activities may help a person relax the mind, which may help retrieve forgotten memories.

Family support is also crucial. Showing the person photographs of past events, exposing them to familiar smells, and playing familiar music may help.

There are currently no drugs available for restoring memory lost due to amnesia. However, there are treatments for the underlying causes.

For example, Wernicke-Korsakoff syndrome (WKS) can involve memory loss due to a thiamin (vitamin B1) deficiency, so targeted nutrition that supports any nutritional deficits can help. Whole grain cereals, legumes (beans and lentils), nuts, lean pork, and yeast are rich sources of thiamin. Those with WKS also need to stop drinking alcohol.

Patients with amnesia due to head trauma may need surgery to remove blood buildup in the brain. Patients with encephalitis may need anti-inflammatory medications.

Prevention of Amnesia

A person can help reduce the risk of amnesia by:

• Eating a balanced diet that includes leafy green vegetables and avoids saturated fats to help prevent cardiovascular problems that can contribute to memory problems.
• Getting medical attention if there’s a high fever, stiff neck, or severe headaches, which can be a sign of an infection affecting the brain.
• Having eyes checked annually to help prevent falls, especially if above the age of 65 years.
• Exercising regularly to reduce the risk of a stroke.
• Getting psychological treatment or encouraging a friend or loved one to seek treatment if they have experienced trauma. 
• Using protective headgear during activities that could result in a brain injury, such as cycling, skating, skiing, or playing contact sports.
• Wearing a seatbelt while traveling in a motor vehicle, and never driving while under the influence of alcohol or drugs.

 

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