[A case of brain herniation due to delayed bone flap sinking].

Marked depression of the skin flap after external decompressive craniotomy, affecting the brain function, is known as sinking flap syndrome. However, to our knowledge, there have been no reports of delayed sinking of the entire bone flap after the procedure, inducing neurological symptoms. We encountered a patient with neurological symptoms due to sinking of the entire bone flap 15 years after the first operation.