When people lose their ability to memorize information or recall information that is stored in memory, they have amnesia. Although amnesia is a popular theme for movies and books, it is a very rare condition.
Being a little forgetful is completely different to having amnesia. Amnesia refers to a large-scale loss of memories that should not have been forgotten. These may include important milestones in life, memorable events, key people in our lives, and vital facts we have been told or taught.
People with amnesia also find it hard to imagine the future, because our constructions of future scenarios are often based on 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.
Here are some key points about amnesia. More detail and supporting information is in the main article.
- Amnesia is an inability to lay down new memories and/or recall old memories
- Other symptoms of amnesia can include confusion and uncoordinated movements
- Alcohol abuse can lead to a type of amnesia known as Wernicke-Korsakoff's psychosis
- Amnesia can be caused by many things including traumatic experiences and brain injury
- The majority of amnesia cases resolve without treatment
Symptoms of amnesia
Amnesia is a rare condition.
The following are common symptoms of amnesia:
- The ability to learn new information is impaired (anterograde amnesia)
- The ability to remember past events and previously familiar information is impaired (retrograde amnesia)
- False memories - these may be either completely invented or consist of real memories misplaced in time (confabulation)
- Uncoordinated movements, sometimes tremors (neurological problems)
- Confusion or disorientation
- Problems with short-term memory
- Partial loss of memory
- Total loss of memory
- Failure to recognize faces
- Inability to recognize places
Amnesia is different from dementia. Although dementia includes memory loss, it also involves other important cognitive problems that may affect the patient's ability to carry out daily activities.
Types of amnesia
There are many different types of amnesia. Below is a list of the most common ones:
- Anterograde amnesia - the patient cannot remember new information. Things that happened recently, information that should be stored into short-term memory disappear. This is usually caused by brain trauma (brain damage from a blow to the head, for example). However, a patient with anterograde amnesia can remember data and events that happened before the injury.
- Retrograde amnesia - often thought of as the opposite of anterograde amnesia. The patient cannot remember events that occurred before their trauma but remembers things that happened after it. In very rare instances, both retrograde and anterograde amnesia can occur together.
- Transient global amnesia - a temporary loss of all memory. The patient with transient global amnesia also finds it very hard to form new memories (severe anterograde amnesia). The loss of past memories is milder. This is a very rare form of amnesia and is most likely to occur in older adults with vascular (blood vessel) disease.
- Traumatic amnesia - memory loss caused by a hard blow to the head; for instance, a car accident. People with traumatic amnesia may experience a brief loss of consciousness, or even go into a coma. In the majority of cases, the amnesia is temporary - how long it lasts usually depends on how severe the injury is. Sports scientists say that amnesia is an important indicator of concussion.
- Wernicke-Korsakoff's psychosis - this is caused by extended alcohol abuse. The disorder tends to be progressive, gradually worsening over time. Patients with Wernicke-Korsakoff's psychosis also tend to 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 - this is a very rare phenomenon. Patients forget not only their past but their very identity. A person could wake up and suddenly not have any sense of who they are - even if they look in the mirror, they do not recognize their own reflection. All the details in their wallet - driving license, credit cards, IDs - are meaningless. This type of amnesia is usually triggered by an event that the person's mind is unable to cope with properly. In most cases, their memory either slowly or suddenly comes back within a few days. However, the memory of the shocking event itself may never come back completely.
- Childhood amnesia (infantile amnesia) - the patient cannot recall events from early childhood. Experts say this type of amnesia may be associated with language development. Others say it is possible that some memory areas of the brain were not fully mature during childhood.
- Posthypnotic amnesia - events during hypnosis cannot be recalled.
- Source amnesia - the person can remember certain information but does not know how or where they got that information.
- Blackout phenomenon - amnesia caused by a bout of heavy drinking. The individual cannot remember chunks of time during the binge.
- Prosopamnesia - the person cannot remember faces. People can either acquire prosopamnesia or be born with it.
Causes of amnesia
Any disease or injury that affects the brain can interfere with the intricacies of 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 our emotions and memories.
Causes of medical amnesia
Some head injuries cause amnesia.
This refers to amnesia caused by brain injury or damage. Possible causes are:
- Encephalitis - brain inflammation. This can be caused by a viral infection, such as herpes simplex (HSV), or an autoimmune reaction to cancer in another part of the body (paraneoplastic limbic encephalitis, PLE).
- Celiac disease - although no clear link has been completely agreed on, researchers report that people with celiac disease commonly seek medical help for amnesia, confusion, and personality changes.
- Oxygen deprivation - any illness or situation which undermines the supply of oxygen to the brain, such as a heart attack, respiratory distress, or carbon monoxide poisoning.
- Some medications - such as the sleeping drug, Ambien.
- Subarachnoid hemorrhage - bleeding in the area between the skull and the brain.
- A brain tumor that lies in a part of the brain important for memory.
- Some seizure disorders.
- ECT (electroconvulsive therapy) - also known as electroshock therapy. This is a psychiatric treatment in which seizures are induced for therapeutic effect on anesthetized patients. The memory loss is nearly always temporary.
- Head injuries - such as those that occur in car accidents, can lead to memory problems. In most cases, the amnesia is not severe and is not long-lasting.
Causes of psychological amnesia
Also known as dissociative amnesia, this is caused by an emotional shock, such as:
- Being the victim of a violent crime
- Sexual abuse
- Child abuse
- Being involved in combat (soldiers)
- Being involved in a natural disaster
- Being present during a terrorist act
The list is endless - in simple terms, any intolerable life situation which causes severe psychological stress and internal conflict. In general, amnesia caused by psychological stressors disrupt personal, historical memories rather than interfere with laying down new memories.
Diagnosis of amnesia
Initially, a doctor will need to rule out other possible causes of memory loss, including dementia, Alzheimer's disease, depression, or a brain tumor. The doctor will require a detailed medical history - this may be difficult if the patient does not remember things, so family members or caregivers may also have to be present.
A doctor will need the patient's permission to talk about their medical details with somebody else.
The doctor will cover the following issues:
- Can the patient remember recent events, and/or remote events (events further back in time)?
- When did the memory problems start?
- How did the memory problems evolve?
- Were there any factors that may have caused the memory loss, such as a head injury, surgery, or stroke?
- Is there a family history of any neurological or psychiatric diseases or conditions?
- Details about the patient's alcohol intake
- Is the patient currently on any medication?
- Has the patient taken illegal drugs, such as cocaine or heroin?
- Are the patient's symptoms undermining their ability to look after themselves?
- Does the patient have a history of depression?
- Has the patient ever had cancer?
- Does the patient have a history of seizures?
The physician may also carry out a physical exam. This might include checking the patient's:
- Sensory function
- Some other aspects of the brain and nervous system
The doctor may also check the patient's:
- Short-term memory
- Long-term memory
The memory assessment will help determine the extent of memory loss. This will assist in deciding on the best treatment.
To find out whether there is any physical damage or brain abnormality, the doctor may order:
- An MRI scan - a machine uses a magnetic field and radio waves to create detailed images of any part of the body; in this case, the brain.
- A CT scan - a medical imaging method that employs tomography. Tomography is the process of generating a 2-D image of a slice or section through a 3-D object (a tomogram). A CT scan is good at detecting bleeding in the brain (especially from injury).
- An EEG (electroencephalogram) - this provides an image of the brain while the patient is performing a cognitive task - a task that requires thinking. It allows the doctor to detect the location and magnitude of brain activity involved.
Blood tests may also reveal the presence of any infection or nutritional deficiencies.
Treatments for amnesia
Fortunately, in the majority of cases, amnesia resolves itself without treatment. However, if an underlying physical or mental disorder is present, it should be treated (if possible).
Psychotherapy may sometimes be effective for some patients. Hypnosis can be an effective way of recalling memories that have been forgotten.
Family support is crucial in helping a patient with amnesia get better. Psychologists and psychiatrists say that reality orientation aids such as photographs, smells, and music can help.
Amnesia 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 various strategies for organizing information so that it is easier to store.
- Learning how to make the best use of digital aids, such as smartphones. With the right training, even patients with severe memory loss can become quite competent with day-to-day tasks. The smartphone can be used to remind the patient about important events, when to take medications, appointments, and key commitments. Patients who cannot remember people's names or faces can store a long list of photographs of faces and check them whenever they wish.
There are currently no drugs for the restoration of memory in patients with amnesia. Because Wernicke-Korsakoff syndrome involves a thiamin (vitamin B1) deficiency, targeted nutrition can help. Whole grain cereals, legumes (beans and lentils), nuts, lean pork, and yeast are rich sources of thiamin.