Amnesia is a temporary or permanent loss of memory. It usually results from an impairment of the brain brought on by a medical condition, such as a blow to the head (traumatic brain injury) or the use of certain substances (e.g., drugs, alcohol). In some relatively rare cases, psychological trauma can trigger amnesia.
Many different types of amnesia can result from a brain injury, including:
- Anterograde amnesia. Memory loss related to events that occur after damage to the brain. Anterograde amnesia involves the inability to learn and recall new information.
- Retrograde amnesia. Memory loss related to events that occurred before damage to the brain. Patients are unable to retrieve long-term memory of events and information learned prior to the brain trauma.
- Transient global amnesia. Sudden and temporary loss of the ability to store new memories of events that occur during the episode.
In rare cases, some patients experience memory loss as a result of dissociative disorders. These occur when people frequently escape reality by suppressing their memories or taking on alternate identities and do not involve medical trauma to the brain.
Amnesia manifests in different ways. Typically, patients forget details of past events that occurred in their lives, are unable to recall information they learned in the past or have difficulty learning and recalling new information. The extent of memory loss is usually correlated with the nature and severity of the injury or trauma that triggered the amnesia.
Patients who experience unexplained memory loss should see a physician, who will perform a complete physical and mental examination and compile a thorough medical history. Tests such as a computed axial tomography (CAT) scan and psychological testing may also be performed to help determine the cause of the amnesia.Amnesia is usually temporary and lasts from only a few minutes to several hours before disappearing on its own. However, psychotherapy is sometimes used to help patients recover from amnesia, and some forms of damage to the brain can result in memory loss that is permanent.
Amnesia is a loss of memory that most commonly results from a medical condition (e.g., a blow to the head) or the use of certain substances (e.g., drugs, alcohol). Less frequently it may be related to severe emotional trauma. People who have amnesia are unable to recall certain past events or information they previously have learned or have trouble forming new memories.
Memory is a process that occurs when the brain records and stores recollections of important information, events and people. Memory is divided into immediate memory (events that happened in the previous few seconds), intermediate memory (events that happened in the preceding few seconds to the last few days) and long-term memory (events that happened further back in time).
Despite this process of recording information, most people forget things from time to time. Amnesia is a more serious form of memory loss that causes significant impairment to a person’s ability to interact socially or to perform job-related tasks. A person with amnesia may lose the ability to recall large portions of memory.
In most cases, amnesia is temporary and lasts from only a few minutes to several hours before disappearing on its own. However, some forms of damage to the brain can result in amnesia that is permanent. In some cases, amnesia is a symptom that occurs with other mental disorders, such as delirium or dementia. In those cases, the underlying condition must be identified and the amnesia may not subside.
Types and differences of amnesia
There are many different types of amnesia that can cause memory loss to a patient after the brain has been injured. Some of the major forms of amnesia related to brain injury include:
- Anterograde amnesia. Memory loss related to events that occur after damage to the brain. Anterograde amnesia involves the inability to learn and recall new information. Patients typically struggle to remember day-to-day events, but have less difficulty remembering events from their childhood.
- Retrograde amnesia. Memory loss related to events that occurred before damage to the brain. Patients are unable to retrieve long-term memory of events and information that occurred prior to the brain trauma.
- Transient global amnesia. Sudden and temporary loss of the ability to store new memories, usually due to a malfunction of the temporal lobe brought on by seizures, delirium or transient ischemic attacks (temporary disturbance of blood supply to an area of the brain). Patients with transient global amnesia often find themselves confused about time and place and may struggle to identify other people. Episodes tend to occur just once during a person’s lifetime and may last for anywhere from 30 minutes to 12 hours. Transient global amnesia can be disorienting while it lasts, but full recovery typically occurs.
Potential causes of amnesia
The mechanisms that cause amnesia are only partially understood, but the condition itself usually results from damage to the brain. The temporal and frontal lobes of the brain are primarily responsible for storing and retrieving information. However, memory is interwoven with many different brain functions and damage to virtually any part of the brain can trigger amnesia.
The brain can be damaged in many ways. For example, amnesia may occur following a severe blow to the head, a condition known as a traumatic brain injury. In some cases, these blows are severe and can lead to medical conditions such as coma. However, a lesser blow to the head that does not cause loss of consciousness can also trigger symptoms of amnesia. Car crashes, bicycle accidents, falls and sports mishaps all can result in blows to the head that may cause amnesia.
Many different conditions can also contribute to amnesia, especially those associated with deliriumand/or dementia. Conditions that may contribute to amnesia include Alzheimer’s disease, tumors or infection in the brain, herpes encephalitis (inflammation of the brain caused by herpes simplex 1 virus), strokes or transient ischemic attacks (temporary reductions in flow of blood to the brain) and neurodegenerative illness.
Drug and alcohol abuse can lead to brain injuries that also cause amnesia. In particular, hallucinogens such as LSD or PCP can alter brain chemicals, making it more difficult for the person to recall memories. Certain legal drugs – including drugs used in general anesthesia, barbiturates and benzodiazepines – can also cause amnesia. Alcoholism may result in a condition called Wernicke-Korsakoff syndrome, which is characterized by memory loss.
In rare instances, Dissociative disorders(e.g., Dissociative amnesia, Dissociative identity disorder) may cause people to lose their memory. These disorders occur when people frequently escape reality by repressing their memories or taking on alternate identities, and do not involve medical trauma to the brain.
The aging process can cause some symptoms associated with amnesia, such as difficulty learning new materials and greater difficulty in recalling learned material. However, aging itself should not lead to significant amnesia.
Other sources of amnesia include severe emotional trauma and seizures.
Signs and symptoms of amnesia
Amnesia manifests in different ways. Typically, patients forget details of past events that occurred in their lives, are unable to recall information they learned in the past, or are unable to learn and recall new information. The extent of memory loss depends on the nature and severity of the injury or trauma that triggered the amnesia. In some cases, amnesia may also impair the patient’s ability to learn new information. Some patients may be aware of their memory loss and try to account for it or lie about periods of time they cannot recall.
In some cases amnesia comes on slowly, whereas in others it appears suddenly. Symptoms of amnesia may be temporary or permanent.
Diagnosis methods for amnesia
Patients who experience unexplained memory loss should see a physician, who may perform a complete physical and mental examination and compile a thorough medical history. A physician who suspects amnesia may ask some of the following questions:
- Has the patient suffered a head injury or emotional trauma?
- Has the patient undergone recent surgery?
- Does the patient use alcohol or drugs?
- Can the patient remember recent events or events from their past?
- Does memory loss pertain to events prior to a specific experience?
- Does memory loss pertain to events after a specific experience?
- Has memory loss gotten worse over time?
- Is memory loss present at all times or only during distinct periods?
- What other symptoms are present?
Other tests may be used to rule out other mental disorders. If amnesia is suspected, the patient will likely undergo a neurological examination and diagnostic tests. These tests can reveal damage in the brain that might be the source of the amnesia. Tests may include:
- Cerebral angiography. A test in which contrast dye is injected into one or both of the carotid or vertebral arteries in the neck. This allows arteries to be seen on x-rays.
- CAT (computed axial tomography) scan or magnetic resonance imaging (MRI) of the head. A CAT scan is a more sensitive imaging technique than a standard X-ray that provides high-definition images of bony structures and soft tissues. An MRI uses powerful magnets and radio waves to create images of the body.
- Electroencephalogram (EEG). An EEG detects abnormalities in the electrical activity of the brain.
Lumbar puncture. A procedure in which cerebrospinal fluid is obtained to check for the presence of disease or injury.
- Psychological testing.
- Blood testing.
In addition, the patient may undergo testing of recent, intermediate and long-term memory.
Treatment options for amnesia
In many cases, amnesia clears on its own and requires no treatment. However, if an underlying physical or mental disorder is detected, it should be treated if possible. Psychotherapy is also sometimes used to help patients recover from amnesia. In particular, hypnosis may help patients recall memories they have forgotten.
Family support can be a crucial element in helping a patient to recover from amnesia. An approach called reality orientation aids in easing patients back into their environment by surrounding them with familiar music, objects and photographs.
Some forms of amnesia result in permanent memory loss that cannot be treated. However, even in such cases, patients may be helped with the use of memory aids and a structured environment.
In addition, researchers are currently studying the effectiveness of medication in improving memory loss in patients who sustained traumatic brain injuries.
Questions for your doctor regarding amnesia
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients and their families may wish to ask the doctor the following amnesia-related questions:
- What tests will you perform to look for signs of amnesia?
- Is it possible that conditions other than amnesia could be causing my symptoms?
- What type of amnesia do I have?
- What do you suspect is the cause of my amnesia?
- Which part of my memory has been affected – short-term, intermediate or long-term?
- What treatments are best for my type of amnesia?
- Will I require psychotherapy as part of my recovery?
- What can I do to try to coax back my missing memories?
- Are there certain day-to-day precautions I need to take because of my amnesia?
- How likely is it that my amnesia will go away at some point?