Man-made head holes
Burr holes are holes bored through your skull & are drilled if your brain is swelling.
There's not much extra room in the cranium. Swollen brains will ooze through the hole at the base of your skull leading to the spinal cord. This is called herniation, a process immediately preceding death. Burr holes are used to relieve swollen brain pressure (high intracranial pressure) & can be lifesaving.