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A craniotomy is the surgical removal of a section of bone (bone flap) from the skull for the purpose of operating on the underlying tissues, usually the brain. The bone flap is replaced at the end of the procedure. If the bone flap is not replaced, the procedure is called a craniectomy. A craniotomy is used for many different procedures within the head, for trauma, tumor, infection, aneurysm, etc.


Figure 1 - Infant skull as seen from the side. The bones of the skull are labeled. T. Graves Figure 2a - The adult skull as seen from the front. T. Graves
Figure 2b - The adult skull as seen from the side. T. GravesFigure 2c - The adult skull as seen from the back. T. Graves
Figure 3 - Brain seen from the side. The four lobes of the brain are indicated as well as the cerebellum and the midline brainstem. T. Graves Figure 4 - The falx separates the cerebral hemispheres while the tentorium separates the cerebral hemispheres from the cerebellum. Note that on the left side the tentorium can be partially seen through. Note also the opening in the tentorium for the brainstem. T. Graves


There are a variety of lesions (abnormalities) that affect the skull and its contents that require a craniotomy or craniectomy for exposure or removal.

Figure 5 - Two metastatic tumors to the brain removed using frameless stereotaxic image guided surgery through small craniotomies (4 by 4 cm). Cerebrospinal fluid fills the cavities left by removal of the tumors. The small craniotomies directly over the tumors allowed the patient to be discharged the day after surgery. Figure 6 - Large benign tumor (meningioma) before and after removal. The cavity formed by removal of the tumor is filled with cerebrospinal fluid.

Click Below to view Animation

Figure 7 - Angiogram of the vessels at the back of the brain showing an aneurysm at the junction of the vertebral artery and posterior inferior cerebellar artery (PICA). Inset shows the position of the temporary (dotted line) and permanent (solid line) clips shown in the video of Figure 8. Figure 8 - Frame from a video of an operation for clipping of the posterior inferior cerebellar artery (PICA) aneurysm seen in figure 7. Note the use of a temporary clip across both the aneurysm neck and PICA. The temporary clip is used to protect the aneurysm from rupture while the aneurysm is manipulated for placement of the permanent clip that clips the aneurysm and leaves the PICA open.
Figure 9 - An arteriovenous malformation. The arterial blood flows directly into veins.


Figure 10 - Outline of a fronto-temporal craniotomy. The small circles indicate bur holes. The darker blue area indicates where bone is removed and not replaced. The dark blue line indicates where the bone is cut. The light blue area is replaced after the surgery. T. Graves Figure 11 - Outline of a midline suboccipital craniectomy. Note the bur holes that are used to start the bone removal. The blue area indicates the bone removed. T. Graves
Figure 12 - Photograph of an air drill making a bur hole. Figure 13 - Wire Gigli saw for cutting bone.
Figure 14 - Operative photograph showing the Gigli saw being used. Figure 15 - Air craniotome being used in surgery.
Figure 16 - The cut bone is elevated. Figure 17 - MRI obtained after partial removal of a malignant brain tumor (glioblastoma multiforme) in which the tumor was treated with absorbable wafers (arrows) impregnated with an anticancer drug. Courtesy A. Sloan, M.D.
Figure 18 - Titanium mesh cranioplasty used for replacement of an infected bone flap.

Figure 19

  1. MRI of left frontal metastatic brain tumor (arrow). Note: MRI images show the left side to the viewer's right
  2. Computer screen as seen by the neurosurgeon during image guided surgery. Note the images have been flipped from side to side so that the surgeon has a left sided image to his own left side. The arrows point to a yellow line that represents the direction of 'attack' chosen by the surgeon. The red 'cross hairs' is the position of the instrument being used by the surgeon. The right lower image shows the skin surface of the patient with multiple donut shaped feducials on the surface. The red asterisk lies on the tumor imaged in blue
  3. Post-operative MRI showing complete removal of the tumor


Complications following craniotomy are primarily related to involvement of the brain and its coverings. Some of the complications are:


Further care