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a computer system. This will make a virtual model of the brain along with a virtual model of the tumor, while at the same time mapping the functional areas of the brain. If the tumor resection is contemplated, this will allow for exact localization and to plan a path through "silent" areas of the brain. These tests are not always necessary but help when the tumor is in special locations. Even if the tumor is located in the most functional part of the brain, operations can be performed with the patient awake and stimulating the brain making sure the areas of resection are not functional. Sometimes this cannot be done. At times the mass may be in a very difficult location to resect or there may be multiple masses or the patient may not tolerate a formal craniotomy. In these instances a stereotactic brain biopsy can help make the diagnosis.
STEREOTACTIC BRAIN BIOPSY
The stereotactic brain biopsy is a brain operation. It is a limited operation, but it is a brain operation. Although done with the patient awake, through a very small hole it does have risks. The most important risk is intracranial hemorrhage. This hemorrhage does not always happen at the time of the biopsy, but may happen several hours afterwards. If the hemorrhage is large enough the patient may actually need a formal craniotomy, if possible, to remove the blood clot. Sometimes the patient deteriorates without a hemorrhage and this may be due to increased swelling of the brain because the brain is very sick and cannot take any additional insult such as the biopsy needle. If a hemorrhage does not occur, the next complications of a stereotactic brain biopsy, is a biopsy that is non-diagnostic. Usually the pathologist examines the initial biopsy to let the neurosurgeon know if the tissue is diagnostic or not. It is normal to not make a final diagnosis based on the very small sample obtained and quickly looked at by the pathologist. Sometimes the masses have different characteristics within themselves. Since the sampling is of a very small area this may lead to different grades of the same tumor type. Other risks include infection, stroke, cranial nerve deficit, death, seizure and cerebrospinal fluid leak.
STEREOTACTIC PROCEDURE:
The patient is usually brought into the holding area or the operating room. The patient is made sleepy, and then screwing four posts into the outer table of the skull after numbing the skin places a metal box. The patient is then taken to the CT scanner or the MRI scanner and the coordinates obtained for the mass. These coordinates localize the mass in 3D space in relationship to the frame. The patient is then brought back into the operating room. The patient's head is then affixed to the operating room table and a special arc is placed on the frame, in order to be able to find the previously obtained coordinates. Minimal hair is shaved. A very small incision is made and then a very small hole in the skull is made. The blunt biopsy needle is placed into the mass and a specimen obtained for the pathologist. Next, there is usually a longer waiting time until there is good confirmation of tissue. A single stitch is usually placed into the previous incision. The head frame is taken off of the patient. The patient is brought to the recover room. There is usually a CT scan performed several hours after the biopsy. The CT scan will not only confirm if there has been any unusual bleeding but also insures that the small amount of bleeding and air present is in the part of the brain that corresponds to the biopsy site. The patient can then be discharged the following day.
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