What is amnesia?
Amnesia means partial or total loss of memory. Depending on the cause, amnesia may be temporary or permanent. It can affect the ability to form new memories (known as anterograde amnesia) or the ability to remember things from the past (retrograde amnesia).
Treatment of amnesia depends on the cause. If amnesia is ongoing it can be distressing for both the affected person and their family and friends. Support from a counsellor or psychologist may help manage the symptoms.
The exact symptoms of amnesia and how severe they are will depend on the cause.
Amnesia frequently involves loss of recent memories as well as the ability to retain new information. Longer-term memories are affected less often.
People with amnesia can appear confused or disoriented due to their memory problems. But their intelligence, personality, general knowledge and ability to communicate and learn skills is generally not affected.
It’s important to note that amnesia is not the same as dementia. Both conditions affect memory, but amnesia is a problem that only affects memory, while people with dementia also have other symptoms, such as problems with thinking and language.
Causes of amnesia
The process of memory is complex and not fully understood. Several different areas of the brain are involved, so damage to any of these areas can affect the ability to form and retrieve memories.
Many things can cause amnesia, including the following.
- Injuries to the brain, including concussion.
- Brain infection or inflammation (encephalitis).
- Drugs and medicines such as sedatives.
- Transient global amnesia (TGA) – see below.
- Underactive thyroid gland (hypothyroidism).
- Ongoing alcohol abuse that results in thiamine (vitamin B1) deficiency.
- Psychological or emotional shock or trauma (this is known as dissociative amnesia, which is rare – see below).
- Brain tumour.
- Stroke or mini-stroke (TIA).
In dementia, including Alzheimer’s disease, recent memories are often lost first, while the memory of things in the distant past can remain crystal clear. People with dementia have a gradual onset of symptoms that include memory problems but other problems as well, such as problems with language and thinking.
Sometimes depression can also result in memory problems, but again, there will be other symptoms that can help differentiate between amnesia and depression.
Tests and diagnosis
If you (or someone you are with) have a sudden onset of memory problems, you should seek immediate medical attention, as the memory problems may be due to a serious medical condition. Call 000 for an ambulance or go to your local hospital emergency department.
You should visit your GP (general practitioner) for memory problems that you’ve noticed developing over time. Take someone you are close with when you see the doctor, as it may be difficult to answer some questions while you are having memory difficulties.
The doctor will want to know about your symptoms, how long you have had them and whether they are getting worse (and how quickly). They will ask about your general health and whether you’ve had a recent head injury. Information about any medicines or other drugs you take will also be important.
Your doctor may perform a brief memory test to assess which parts of your memory are most affected. They may also test your thinking and judgement. A physical examination will also be done to help work out the cause of the problem.
Tests that may be recommended to look for possible causes of amnesia include the following.
- MRI or CT scan of the brain.
- Electroencephalogram (EEG), a test that measures the brain’s electrical activity and can detect seizure activity.
- Blood tests.
Treatment of amnesia
Treatment of amnesia will depend on the cause.
There are some self-care strategies for people with ongoing memory problems. These include using memory aids (reminders on a smartphone, a calendar and other notes to jog your memory).
In some cases, it may be helpful to work with a therapist to do memory training.
Transient global amnesia
An alarming but non-serious form of amnesia is known as transient global amnesia (TGA). TGA is a sudden, temporary episode of memory loss that usually affects people aged 50 to 70 years.
People with TGA have an episode where they are unable to form new memories and may sometimes also lose recent memories extending as far back as weeks or months. The episode of amnesia comes on suddenly (over minutes or hours). It may last for a period of 4 to 6 hours, but sometimes up to 24 hours.
Transient global amnesia symptoms
People with transient global amnesia will usually keep repeating questions, such as ‘Why am I here?’, ‘How did I get here?’ or ‘What time is it?’, as they cannot remember the answers. They often appear anxious, agitated and perplexed.
The ability to do learned activities, such as driving, is generally not affected. People also usually remember who they are and recognise people they know well.
Sometimes symptoms such as nausea, dizziness and headache occur with TGA.
People with TGA usually don’t remember the episode afterwards. Understandably, this is a very frightening experience for both for the affected person and those around them.
The exact cause of transient global amnesia is not known. Migraine, seizures, and changes in the blood circulation in the brain have all been investigated as possible causes, but more research is needed.
TGA can be brought on by extreme physical activity, very stressful events, pain, sudden immersion in cold or hot water, accidents or strong emotional experiences.
Treatment and recovery
There is no specific treatment for transient global amnesia. Symptoms usually get better on their own within hours or days. Sometimes mild memory problems persist for weeks.
There is a small risk of a repeat episode, but the risk of having more than 2 episodes is extremely rare.
Dissociative amnesia is one of several dissociative disorders that usually develop after trauma, as a way of coping. They involve escaping reality in ways that are involuntary and cause stress or problems with day-to-day functioning (for example in relationships or at work).
Dissociative amnesia usually involves loss of memory of a traumatic event, but sometimes also involves more general memory loss about yourself and people in your life from that time.
Treatment for dissociative amnesia may involve psychotherapy (talking therapy) or possibly hypnosis in some cases. Sometimes medicines such as antidepressants or anxiety medications are recommended.
What to do if you or someone else has sudden memory loss
Some potentially life-threatening conditions can cause sudden memory loss, so it’s important to seek immediate medical attention if you or someone you know has sudden memory loss.