Great strides have been made in the surgical treatment of brain tumors over the past few decades. Computer systems have been developed to precisely guide the surgeon to the tumor. Tools for the removal of the tumor have been developed that minimally interfere with the functioning of the surrounding brain tissue. As a result, families should have an optimistic outlook for their child with a tumor in the brain.
In the 1970s the surgical microscope was introduced into the neurosurgical operating room. This equipment provides much better illumination of the surgical field and with its magnification allows the surgeon to be much more precise in manipulating brain tissue. It has significantly decreased injury to the brain during the removal of tumors. In the 1980s both the surgical laser and the ultrasonic aspirator were introduced into our operating rooms. The laser is essentially a very small knife. It can be used in tight spaces in a very controlled fashion to remove small pieces of tumor or make precise incisions through brain tissue. There are several different types with each having advantages in particular applications. The ultrasonic aspirator emits a sonic wave that breaks up tissue cells, injects fluid to create a slurry of the broken-up cells, and then aspirates them. It is a gentle process that can be controlled to such a degree that it can be used immediately adjacent to a blood vessel without injuring it. Its use has allowed us to work within tight spaces such as the brain stem and spinal cord.
During the 1990s several technologies developed to inform the surgeon of the location of the tumor gained wide acceptance by neurosurgeons. First was the operative ultrasound. This tool is very similar to sonar used by ships to peer through water. It emits sound waves that bounce off objects within the brain. A receiving probe gathers this information and presents it to a computer, which then generates a picture. This machine can be used by a surgeon to determine a path to the tumor, calculate the distance it is away, and confirm the completeness of the resection. Also introduced in the early 1990s was a technology termed “computer assisted navigation.” This consists of a computer system that can show precisely on an MRI scan where a surgeon is working and, using a pointer, show the surgeon the direction to the tumor and confirm that the resection cavity encompasses all the space that the tumor resided in prior to its removal. This system also allows the surgeon to plan where the scalp incision and entry through the bone would best be positioned.
More recently, mapping the location of various components of the nervous system and monitoring their integrity during surgery has become possible. Mapping refers to electrically stimulating regions of the nervous system to identify locations of nerves responsible for a given function. An example would be stimulating the brain stem to locate the area responsible for facial movement. One would observe facial movement, or an electrode inserted into facial muscle would record muscle contraction when the appropriate area of the brain stem was stimulated. Monitoring refers to stimulating a nerve continuously so that it transmits a signal repeatedly and recording that signal to confirm the nervous system's continued ability to do this as the surgery progresses. An example would be stimulating the area of the brain responsible for moving the leg as surgery within the brain stem progressed. The pathways the brain uses to tell the leg to move pass directly through the brain stem. As long as one can continue to record the signal in the leg muscles resulting from stimulating the brain, the surgeon knows that the surgery is not paralyzing the patient.
After surgery, tumor specimens will be sent to the pathologist for microscopic analysis. The pathologist will both classify the tumor and grade it or determine whether the tumor is benign or malignant. Many centers also save a portion of the tumor to be placed in a tumor bank. Here the tumor is kept in a frozen state, and it can be both analyzed and grown in special culture media in the future, allowing scientists to learn more about a class of tumor growth characteristics.