Craniotomy is any bony opening that is cut into the skull. A section of skull, called a bone flap, is removed to access the brain underneath. There are many types of craniotomies, which are named according to the area of skull to be removed . Typically the bone flap is replaced. If the bone flap is not replaced, the procedure is called a craniectomy.

Craniotomies are also named according to their size and complexity. Small dime-sized craniotomies are called burr holes or keyhole craniotomies. Sometimes stereotactic frames, image-guided computer systems, or endoscopes are used to precisely direct instruments through these small holes. Burr holes or keyhole craniotomies are used for minimally invasive procedures to:

  • insert a shunt into the ventricles to drain cerebrospinal fluid (hydrocephalus)
  • insert a deep brain stimulator to treat Parkinson Disease
  • insert an intracranial pressure (ICP) monitor
  • remove a small sample of abnormal tissue (needle biopsy)
  • drain a blood clot (stereotactic hematoma aspiration)
  • insert an endoscope to remove small tumors and clip aneurysms

Large or complex craniotomies are often called skull base surgery. These craniotomies involve the removal of a portion of the skull that supports the bottom of the brain where delicate cranial nerves, arteries, and veins exit the skull. Reconstruction of the skull base is often necessary and may require the additional expertise of head-and-neck, otologic, or plastic surgeons. Surgeons often use sophisticated computers to plan these craniotomies and locate the lesion. Skull base craniotomies can be used to:

  • remove or treat large brain tumors, aneurysms, or AVMs
  • treat the brain following a skull fracture or injury (e.g., gunshot wound)
  • remove tumors that invade the bony skull
  • There are many kinds of craniotomies. Ask your neurosurgeon to describe where the skin incision will be made and the amount of bone removal.



Duke Samson, MD, UT Southwestern Medical Center at Dallas, performs a frontal craniotomy and removes a meningioma, a benign tumor.