Amnesia: what it is, types, causes and what helps

Headway describes amnesia as literally a lack or absence of memory. Because nobody forgets absolutely everything, it says amnesia refers to a failure of some part of the memory system. The word is sometimes used to mean any kind of memory disorder, and sometimes to mean a very pure memory problem, where memory impairment is the only problem a person faces.

Headway says people who have amnesia are likely to show normal or near-normal immediate memory (for example, they can repeat back a telephone number immediately), have difficulty remembering things after a delay or distraction, have problems learning new things, and remember things that happened some time before their brain injury or illness better than things that happened shortly before it.

The NHS page on memory loss (amnesia) is brief: most people forget things from time to time, but you should see a GP if you keep having problems with your memory, because it could be caused by something that can be treated.

Symptoms depend on the cause. Headway lists features typical of amnesia: difficulty remembering things after a delay or distraction, problems learning new things, better memory for events from long ago than recent ones, normal memory for skills they practised a great deal (such as playing the piano, swimming or driving), and being helped by cues, such as being given the first letter of someone's name.

Where memory loss is part of dementia, the Alzheimer's Society describes forgetting recent conversations or events, struggling to find the right word, forgetting names of people and objects, losing or misplacing items, getting lost in familiar surroundings, forgetting how to carry out familiar tasks, and forgetting appointments. It says memory can be affected in different ways: not being able to create new memories, taking longer to retrieve information, or not being able to retrieve information.

The NHS says memory loss can just be a natural part of getting older. Sometimes it may be caused by something common and treatable such as stress, anxiety or depression, or sleeping problems (insomnia). Occasionally it can be a sign of something more serious, such as dementia.

Headway says the majority of people with memory problems have these problems for a physical reason, such as brain injury or illness, rather than a purely psychological reason. It says that while some people become amnesic for psychological reasons, in real life such people are rare. Headway lists causes of brain injury on its website, including traumatic brain injury, stroke, brain haemorrhage, encephalitis, meningitis, brain tumour and hypoxic brain injury.

The Alzheimer's Society explains that people with dementia often experience memory loss because dementia is caused by damage to the brain, and this damage can affect areas of the brain involved in creating and retrieving memories.

Headway describes post-traumatic amnesia (PTA) as the time after a period of unconsciousness when the injured person is conscious and awake but behaving or talking in a bizarre or uncharacteristic manner, and has no continuous memory of day-to-day events. PTA can sometimes occur without the person having been unconscious beforehand.

It lists symptoms including confusion, agitation, distress and anxiety, uncharacteristic behaviours such as aggression or disinhibition, inability to recognise familiar people and a tendency to wander. Headway says PTA is a stage of recovery that will pass, and suggests staying calm, keeping the environment quiet, reducing the risk of harm and not correcting or forcing the person to remember.

Headway says PTA may last a few minutes, hours, days, weeks or in rare cases months, with usually no way of knowing exactly how long. The duration of PTA, along with length of time in coma, is often a good indicator of the severity of the injury: PTA of more than 24 hours suggests a severe brain injury, whereas less than 1 hour suggests a minor one.

It depends on the cause. For amnesia after brain injury, Headway says personal memories can and do often return after brain injury, sometimes over the course of the initial recovery period, while others may take weeks, months or even years to gradually return. It is common for memories immediately preceding and following the injury to remain forgotten, and some memories may not return or may return less clearly.

Headway says it is perfectly normal to grieve for this loss, and that new memories can still be formed. For memory loss that is part of a progressive condition such as dementia, the Alzheimer's Society describes memory problems that become more persistent and begin to affect everyday life. The NHS says that where the cause is a treatable one such as stress or poor sleep, treatment will depend on the cause.

The NHS says any treatment that is recommended will depend on the cause of the memory problems. Headway says there is no specific or instant cure for memory problems after brain injury, but recovery can occur naturally as the brain heals over time, and addressing other effects such as fatigue or concentration problems may help memory.

Headway describes practical approaches: rehearsing information and practising routines; a family member or friend testing you with successively longer gaps; errorless learning, where information is learned correctly the first time round with gradually reducing help; and external memory aids such as diaries, calendars and to-do lists, as well as technology such as alarms, voice recorders and portable electronic devices.

The Alzheimer's Society offers practical advice and support for people with memory loss in dementia, including tips for supporting someone with memory loss and therapy and approaches for memory loss support.

• Keep a diary or calendar and use alarms or reminders on a phone.

• Rehearse new information and repeat routines.

• Use cues, such as the first letter of a name, to help recall.

• Take photos or keep a diary of new memories and special events.

• Talk to family and friends about memories, and look at photographs or listen to music linked to them.

The NHS says to see a GP if memory problems are affecting your day-to-day life. It is often nothing serious, but it is best to get checked because any treatment you need may work better if started early. If you are worried about an older relative who is becoming increasingly forgetful, it advises speaking to a GP about whether it could be a sign of dementia.

At the appointment, the NHS says a GP will ask you some questions to try to find the cause, and it might be useful to bring someone with you who can help describe the problems. The GP may refer you to a memory specialist for an in-depth assessment, and scans may sometimes be needed.

Sudden memory loss can be an emergency. The NHS says to call 999 if you think someone is having a stroke, which can include confusion and memory loss, face drooping, arm weakness or speech problems, even if the symptoms have stopped. The NHS head injury page says to call 999 for a head injury where someone has been knocked out and has not woken up, cannot stay awake, has a fit, has new numbness or weakness, or has problems walking, balance, understanding or speaking.

On the NHS, a GP is the first step for memory problems, with referral to a memory specialist or memory assessment service for in-depth assessment. After a brain injury, care is led in hospital and then through rehabilitation and community services.

Some people choose a private neurologist, neuropsychologist or memory clinic. If you do, take a list of symptoms, medicines and any relevant history, and share the findings with your GP so that your NHS record is complete. Charities such as Headway and the Alzheimer's Society provide information and support whichever route you use.