What kills after a head injury almost never happens at the moment of impact. It happens in the hours after, while everyone thinks it's over.
ACT
- Don't move the person until you've ruled out a neck injury. Any blow hard enough to hurt the head can have hurt the spine: keep the head in line with the body.
- Check consciousness and breathing. Unconscious: Unconscious person, keeping the head, neck and trunk in line while turning them onto their side.
- Stop scalp bleeding with pressure. It bleeds a lot and looks alarming, but it's rarely the main problem — see Severe external bleeding.
- Note the time of the blow and what happened. Height of the fall, speed, whether they wore a helmet, any loss of consciousness and how long it lasted.
- Ask three simple questions: where are we, what day is it, what happened. Repeat every half hour. It's the comparison between two checks that tells you something, not a single check.
- Keep the person resting, lying down, head slightly raised, and don't leave them alone.
- Give nothing to eat or drink, in case they need an operation.
Get help without waiting if any of these signs appear:
- loss of consciousness, even brief
- repeated vomiting
- increasing drowsiness, difficulty waking the person
- confusion, incoherent speech, unusual behaviour
- a headache that gets worse instead of better
- one pupil larger than the other
- weakness or tingling in a limb
- a seizure
- blood or clear fluid coming from the ear or nose
- double vision, problems with balance or speech
ADAPT
There are no signs and the person seems fine. It's the most common case, and it doesn't excuse you from watching. Twenty-four hours of close watch with someone nearby, including at night. There's no need to keep them awake, but you must be able to wake them and check that they respond normally.
It's a child. The thresholds for worry are lower. A child who cries, asks for things and plays is reassuring. A child who is unusually quiet, hard to wake, or vomits repeatedly is an emergency.
It's an elderly person, or someone on blood thinners. The risk of bleeding inside the skull is clearly higher, and it can show up several days after a seemingly minor blow. Any head injury in this situation calls for medical advice, even without symptoms.
The person has come round and wants to carry on. It's common, and it should be refused. A second blow before full recovery is far more serious than the first. At the slightest doubt, they stop for the day.
You're far from any help. You can't treat anything, only watch and move them. What changes the decision: any sign from the list means you start the evacuation, even at night — see Signaling and getting found.
There's an open wound on the skull or a dent you can feel. Don't press directly on it, don't remove anything, cover it without pressing and get help.
UNDERSTAND
Why things get worse later
The brain is enclosed in a rigid box with no spare room. A blow can tear a blood vessel; blood then slowly builds up between the skull and the brain, and there's nowhere for it to go. The pressure gradually rises and squeezes the brain.
This process takes time — sometimes a few hours, sometimes much longer in an elderly person or someone on blood thinners. That's what produces the typical pattern: a blow, a period where everything seems normal, then a decline.
That's exactly why the watching matters. Without it, the decline is discovered too late.
What the pupils tell you
A pupil that widens on one side only points to pressure on the nerve on that side, and so to rising pressure. It's a late and serious sign. Its absence proves nothing; its presence calls for immediate evacuation.
Concussion
A blow can disturb how the brain works without any visible injury: brief confusion, no memory of the moments before the blow, headache, sensitivity to light, slowness. Recovery takes rest, physical and mental, and comes gradually.
The key point is this: the vulnerability lasts throughout recovery. A second injury during this period has consequences out of all proportion to its own force. That's why nobody goes back to a risky activity until every sign has gone.
Helmets
A helmet doesn't prevent the injury; it reduces the energy passed on and prevents a fracture. That's already a lot. A helmet that has taken a blow has absorbed energy by deforming, sometimes invisibly: it no longer protects and must be replaced.