Stereotactic Surgery

    The concept of stereotactic brain surgery is simple. This technique uses images of the brain to guide the surgeon to a target within the brain. A colorful term for this surgery is neuro-navigation! This technique may utilize an external frame attached to the head (frame-based) or imaging markers attached to the scalp (frameless or image guided surgery) to orient the surgical in his approach. The term "stereotactic" was coined from Greek and Latin roots meaning "touch in space."

    With frame-based stereotactic surgery, a light weight frame is attached to the head using local anesthesia. The head is imaged by CT, MR or angiography to indentify the target in relationship to an external frame. Since both the frame and the target are "seen" in the images, the distance of the target from reference points on the frame can be measure in three dimensions. Any surgical apparatus attached to the head frame can be adjusted to the three dimensional coordinates of the target and the target can be accurately approached by the surgeon. A common example is a stereotactic brain biopsy. Deep tumors within the brain may be difficult and dangerous to approach by an open operation. Using a stereotactic biopsy apparatus fixed to the head frame and adjusted to the target coordinates, a biopsy probe is passed through a small hole in the skull to sample tissue for diagnosis.

   Typical surgical apparatus used by this technique:   

• stereotactic arc to quide biopsy needles and forceps

• electrodes for recording or making lesions
• laser to guide open surgery

• various endoscopes
• Gamma Knife

    The use of this technique has challenged the imagination of neurosurgeons since its first important development by Sir Victor Horsley and James Clarke in the early 1900's:

• neurophysiological research
• functional neurosurgery
  movement disorders: Parkinson's disease
  pain disorders
  emotional disorders: obsessive compulsive disorder
• diagnostic biopsy of brain tumors
• cyst aspiration
• volumetric treatment or removal of tumors
• guidance for open surgery
• radiosurgery

 

    Frameless stereotactic surgery relies on fiducial markers which are taped to the scalp before the brain is imaged. In the operating room the orientation of these markers is used to register the computer containing the brain images. Once registration is completed the computer can show the relationship of our surgical instruments to the imaged brain. This technique can be used for biopsy, functional neurosurgery of accurate removal of large tumor volumes by open surgery.

To the left is a  surgical plan for the biopsy of a tumor of the skull base, just behind the eyes, probably a craniopharyngioma. The software is provided by the Sofamor-Danek Stealth system for frameless, image quided surgery. The proposed trajectory of the biopsy probe is displayed. Prior to surgery any trajectory can be defined, avoiding injury to intervening sturctures within the brain.