Post-traumatic amnesia after head injury: what it is and how long it lasts

Headway defines post-traumatic amnesia as the period after unconsciousness when the injured person is awake and conscious but behaving or talking in a bizarre or uncharacteristic manner. Memory for the present is lost: they may recognise family but be unable to take in that they are in hospital or have been hurt, and may be unable to recall what happened minutes or hours earlier. It can sometimes occur without prior unconsciousness.

Staff on hospital wards often check orientation and day-to-day memory daily, with simple structured questions, to judge when PTA is ending. The time at which continuous memory returns is recorded, because it helps in estimating severity and planning rehabilitation.

Headway lists confusion, agitation, distress and anxiety, uncharacteristic behaviours including aggression, swearing, shouting and disinhibition, inability to recognise familiar people, and a tendency to wander. Some people instead become very quiet, docile, loving, friendly, clinging or childlike. They may attempt to leave hospital, pull at tubes or take off clothing.

Seeing a relative like this is distressing. It helps to know that it is a recognised stage and that the behaviour reflects the injured brain rather than the person's character.

Headway suggests staying as calm as possible, because distress in others adds to confusion, and ensuring a peaceful, quiet environment, since too much stimulation should be avoided. Reducing the risk of harm may mean someone sitting with the person at all times, especially if they wander or try to get out of bed, and a rota of familiar faces by day with an assigned nurse at night can help.

Repeated questions are common. Headway advises that it is best not to correct delusions or try to force memory, as this increases agitation. Instead, give brief, calm, consistent answers and gently orient the person. Relatives are urged to take breaks and share visiting, because exhaustion makes things harder, and to discuss concerns with ward staff.

• Keep voices low and visitors few at a time.

• Use simple sentences and repeat key facts, such as where they are.

• Avoid quizzing the person to test memory.

• Tell staff about wandering, agitation or distress so a safety plan can be made.

PTA can last a few minutes, hours, days or weeks, or rarely months. Certain medicines have been used with varying success, and there is usually no way of knowing in advance how long it will last. Headway says PTA itself has no adverse effects unless the behaviour causes self-injury, but its duration, with the length of coma, is a good indicator of severity.

As rough guidance Headway states that PTA over 24 hours indicates likely severe injury with long-term complications, while less than 1 hour suggests a minor injury. In its severity table, mild injury has PTA under 24 hours and loss of consciousness under 30 minutes, with a Glasgow Coma Scale score of 13 to 15, while moderate and severe injuries involve PTA of 24 hours or more, with scores of 9 to 12 and 3 to 8 respectively. The charity stresses that everyone is different and categories do not always predict long-term effects.

When PTA clears, the person holds on to more information and begins to make sense of where they are and why. Headway says behavioural effects that continue longer are no longer considered PTA but a longer-term effect of the injury. Memory for the PTA period itself is usually patchy or absent, which can be a relief to families, and some experience it as a bad dream.

Rehabilitation planning begins as PTA lifts: assessment by therapists and neuropsychology, graded activity, and attention to fatigue, mood and cognition. Our guides to cognitive rehabilitation and emotional and behavioural change describe what follows.

Confusion after a head injury should always be assessed. The NHS says to call 999 if someone who has hit their head cannot stay awake, has a fit, has clear fluid coming from the ears or nose, has new numbness or weakness, has problems with walking, balance, understanding or speaking, has problems with vision or hearing, or shows a change in behaviour such as becoming more irritable or distracted. It advises NHS 111 for vomiting, dizziness, blood-thinning treatment or other worries, and a GP if symptoms last more than 2 weeks. In hospital, tell staff immediately if the person becomes more drowsy or confused than before.