Sometimes physicians describe their operations in terms that are very foreign to the patient. The following is a primer for patients and their families in neurosurgical procedures which will help them better understand the surgical options for brain tumors.

Craniotomy

This means to make a trap-door in their skull to expose its contents. An incision must be made in the scalp and the scalp is peeled back to expose the bone of the skull. One or several holes (about 1/2 inch in diameter) are made in the skull using a special saw. Then the plate of bone is removed, exposing the outer membrane covering the brain — or dura mater. The dura is cut and the surface of the brain is thus exposed. The operation to remove a brain tumor or perform some other task then proceeds. When this is completed, the dura is usually closed with sutures and the bone plate is replaced. This is held in place with wire or nylon sutures. The scalp is then closed.

Craniotomies are usually named for the part of the skull in which they take place: e.g. Frontal craniotomy, temporal craniotomy, etc.

Stereotactic Biopsy

Stereotactic (from Greek: Stereo-three dimensions; tactic-to probe) is a term to describe procedures done in precise and defined three dimensional space. These are ordinarily done with the patient’s head held in a rigid frame (called a stereotactic frame). The frame is used to direct a probe into the brain through a small hole in the skull. The figure at left shows an axial CT of a patient’s head in a stereotactic frame. The white dots outside the patient’s head are part of the internal calibration of the stereotactic frame.

Volumetric Stereotactic Procedures

Volumetric stereotaxis is a method for gathering, storing and reformatting imaging derived three dimensional volumetric information defining an intracranial lesion with respect to the surgical field. Most importantly, this information is displayed to the surgeon intraoperatively and scaled to the actual size and location of the surgical field. With this technique a surgeon can plan and simulate the surgical procedure beforehand, reach deep-seated or centrally located brain tumors employing the safest and lest invasive route possible.

Why is volumetric stereotaxis necessary?

Intracranial mass lesions are volumes in space. This is easily apparent on review of contiguous CT and MRI slice images of the lesion. However, translation of this three dimensional information from the imaging studies ( CT and MRI) to three dimensional surgical operating space within the patient’s head is difficult and imprecise during an open operation. A surgeon may have difficulty in knowing where tumor ends and normal brain begins; in spite of the fact that this information is usually clear on the imaging studies. Indeed, there may even be difficulty in finding some subcortical tumors.

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