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. 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).
With frame-based stereotactic surgery, a lightweight frame is attached to your head using local anesthesia. Your head is imaged by CT, MRI or angiography to identify the target in relationship to the 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. 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. A common example is 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.This technique is also used to place electrodes in the deep brain to treat movement disorders such as Parkinson's disease.
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. Frameless or image guided surgery is very helpful for the accurate approach and removal of large brain tumors.