A craniotomy is a surgical operation in which a bone flap is temporarily removed from the skull to access the brain. Craniotomies are often critical operations, performed on patients who are suffering from brain lesions, such as tumors, blood clots, removal of foreign bodies such as bullets, or traumatic brain injury (TBI), and can also allow doctors to surgically implant devices, such as deep brain stimulators for the treatment of Parkinson's disease, epilepsy, and cerebellar tremor. The procedure is also used in epilepsy surgery to remove the parts of the brain that are causing epilepsy.
Craniotomy is distinguished from craniectomy (in which the skull flap is not immediately replaced, allowing the brain to swell, thus reducing intracranial pressure) and from trepanation, the creation of a burr hole through the cranium in to the dura mater.
Human craniotomy 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 craniotomy 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 craniotome, 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.)
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