can have other harmful effects. paralysing drugs are only introduced if patients are fully sedated (this is essentially the same as a general anaesthetic) surgery craniotomies are holes drilled in the skull with the help of cranial drills to remove intracranial hematomas or relieve pressure from parts of the brain. as raised icp's may be caused by the presence of a mass, removal of this via craniotomy will decrease raised icp's. a drastic treatment for increased icp is decompressive craniectomy, in which a part of the skull is removed and the dura mater is expanded to allow the brain to swell without crushing it or causing herniation. the section of bone removed, known as a bone flap, can be stored in the patient's abdomen and resited back to complete the skull once the acute cause of raised icp's has resolved. alternatively a synthetic material may be used to replace the removed bone section (see cranioplasty)