Sinking skin flap syndrome or “syndrome of the trephined” is an infrequent complication after a massive skull bone removal, with an invagination of the cutaneous flap, covering the bone defect, with neurological symptoms like mental status change, intense headache, focal neurological deficit or epilepsy.

This condition can appear due to the existence of an atmospheric pressure gradient, especially after CSF diversion procedures such as shunting, dehydration, general CSF hypovolemia, and change of head position.

This case is somewhat unique since the condition appeared after the onset of the right shunt malfunction in the form of hyperdrainage.