Diagram of the elements of a<unk> . Human<unk>  is usually performed under general anesthesia but can be also done with the patient awake using a local anaesthetic; the procedure, typically, does not involve significant discomfort for the patient. In general, a<unk>  will be preceded by an MRI scan which provides an image of the brain that the surgeon uses to plan the precise location for bone removal and the appropriate angle of access to the relevant brain areas. The amount of skull that needs to be removed depends on the type of surgery being performed. The bone flap is mostly removed with the help of a cranial drill and a<unk> , then replaced using titanium plates and screws or another form of fixation (wire, suture, etc.) after completion of the surgical procedure. In the event the host bone does not accept its replacement an artificial piece of skull, often made of PEEK, is substituted. (The PEEK appliance is routinely modeled by a CNC machine capable of accepting a high resolution MRI computer file in order to provide a very close fit, in an effort to minimize fitment issues, and therefore minimizing the duration of the cranial surgery.)
Craniotomy
Cerebrospinal fluid diversion
Cranioplasty
Decompressive craniectomy
Ventriculostomy
Ventriculotomy 
Lumbar–peritoneal shunt
Endoscopic third ventriculostomy