Current surgical techniques for removing a brain tumor involve a variety of technological tools. These tools help the surgeon to enhance the safety of the procedure, while maximizing the degree of resection. This approach has resulted in better outcomes for the patient.
Stereotactic guidance has been one of the technological advances in brain tumor surgery. This is a GPS-like system used in the OR that allows the surgeon to navigate within the surgical field, and see the corresponding location on the MRI, in real time.
Below, the image guided navigation display sollows the surgeon to see where he or she is in the brain, using the MRI as a map.
This case example is a patient with a newly diagnosed tumor in the left hemisphere of the brain. As the patient is right handed, the left hemisphere controls speech production and language comprehension. (The right hemisphere is involved in speech in left-handed persons. I can elaborate more on this in future posts if requested.) Just as critically, in this patient the tumor appears to be within the motor area of the brain, or adjacent to it and pressing upon it. Any damage to the motor area would result in some degree of paralysis on the right side of the body, in this case primarily the arm and hand. This, of course, is to be avoided at all costs.
The problem for the surgeon is that when the brain surface is exposed, its function cannot be determined from its appearance. There aren't labels on the brain like a Google map!
Brain mapping allows the surgeon to determine where certain critical areas of the brain are located, and whether the tumor invades into them. In this case, I used electrical mapping, called evoked potential mapping, to locate the motor area of the brain.
Locating the motor area of the brain is critical. First, of course, this allows the surgeon to avoid encroaching upon, and damaging, the motor area, which would result in paralysis. Second, by knowing where the motor area is, the surgeon knows where the motor area is not, and can therefore resect the tumor as aggressively as necessary. This results in better long term outcomes for the patient. In other words, removing more of the tumor results in better cure.
Motor mapping in this case was done by placing platinum recording electrodes on the brain surface and observing for characteristic patterns in the electical responses which denote the location of the motor and sensory areas of the brain.
The picture below shows the characteristic phase reversal that delineates the transition between the motor and sensory cortex.
Once it was determined that the tumor was not invading the motor or sensory cortex, resection could proceed. The goal is complete resection, based on the borders of the tumor on MRI.
Below, the surface of the tumor is swollen and bulging.
Below, the resected specimen.
Conclusions
This patient was able to undergo a total resection of their tumor, while incurring no neurologic deficit. The application of modern neurosurgical techniques, such as stereotactic guidance and brain mapping, allows for safer brain tumor surgery and more complete resection, which in turn leads to better long-term outcomes for the patient.
