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24Goldman(F)-24CHAPTER10/19/077:52 PMPage 64024Neurologic Surgery.Craniotomy.Definition.A surgical opening of the cranium.Discussion.The most basic form of craniotomy is the burr hole, a limited opening through which blood or fluid may be evacuated or instruments.inserted to divide neural tracts (as in prefrontal lobotomy). Additional.uses of the burr hole include biopsy of an intracranial mass/lesion and.aspiration of the contents of an abscess. A craniectomy refers to the.procedure in which a section of the cranium is removed. Trephination.refers to a procedure performed through burr holes that are larger.than those usually made to perform limited maneuvers.When applicable, a twist drill is used in lieu of a burr. Computed tomography (CT).scan, magnetic resonance imaging (MRI), angiography or magnetoencephalography, electroencephalogram (EEG) mapping, angiographic.stress tests, and ultrasound modalities are employed with tomography.and three-dimensional (3D) coordinates to localize a lesion, i.e.,.stereotactic localization. Image-guided stereotactic burr hole biopsy,.employing a CRW3 (or similar) head frame, provides accurate craniocortical entry transit and targeting minimizing craniocerebral traumaApproaches employing endoscopy and stereotactic procedures.decrease morbidity and mortality; some cranial procedures performed.in specialized radiology departments or specially equipped operating.rooms are “same-day” noninvasive procedures, such as those employing.the Gamma knife. Intracerebral hematomas can be evacuated endoscopically through a burr hole; the cortical incision is approximately 6 mm in.diameter. For removal of an intracranial hematoma, the cortical incision.is made from a location with the shortest trajectory to the clot. Endoscopic instruments, smaller but similar to standard instruments, used to.perform the procedure are inherently less traumatic to the brain. Endoscopic procedures may require more than one burr hole (port)During craniotomy (or burr hole procedure), intracranial pressure, when elevated, is reduced as a result of entry. In addition, as.underlying tissues are manipulated, the location of the previously.defined lesion shifts (thereby deviating somewhat from preoperative.localization studies). In some institutions, highly sophisticated intraoperative MRI systems are in use.This may be in the form of cylindrical.24Goldman(F)-2410/19/077:52 PMPage 641Chapter 24Neurologic Surgery641MRI chamber, a section of which can be advanced for imaging and.retracted to continue the surgery. Another system is one in which reference point electronic sensors are placed about the operative field in.coordination with a computer to provide interactive localizationWhen a limited-access endoscopic procedure is not applicable, burr.holes are made and a portion (a “flap”) of the cranium is lifted after the.bone is cut by craniotome (with periosteum and muscle attached), i.e.,.craniotomy.When decompressive craniotomy is performed, bone (with.overlying soft tissues dissected away) is excised, i.e., craniectomy, and.preserved for later reimplantation. Methods of bone preservation include.placing the skull section in the patient’s subcutaneous tissue, freezing the.bone section (in antibiotic solution), or sterilizing it with ethylene oxide.and holding it in a bone/tissue bank for later reimplantation.When the.bone fragment cannot be retained, a prosthetic substitute is made. The.craniotomy prosthesis can be a plate made of polymethylmethacrylate.(PMMA) cement (fashioned over a mesh frame, i.e., template), titanium,.or Vitallium®, or various plastics may be used for making the substituteBurr holes can be repaired with silicone or other materialsNumerous neurosurgical conditions treated by craniotomy include the following:.Intracranial aneurysm is an arterial dilation secondary to muscular weakness prone to rupture or hemorrhage. Controlling.the blood pressure is essential during the repair.The
