To quote from the BBC: “However, leading neurosurgeon Chris Chandler said a seemingly minor blow on the head can cause life-threatening injuries.
Mr Chandler, from King’s College Hospital in south London, said the effects of a blow to the head may not become apparent until several hours afterwards and, if untreated, a patient can fall into a coma.
“A blow to the head can cause a bruise or rupture a blood vessel that slowly swells, causing pressure to build up inside the skull,” he said.
“In the skull there is nowhere for the brain to move to so pressure continues to grow and that swelling can cause the brain to malfunction because it can limit circulation.
“If that pressure is not relieved it can kill.” ”