A student in the ninth grade class (where Dr. Ravish Patwardhan was a guest lecturer talking about neurosurgery) raised her hand and asked a well-thought-out, obvious question: “How do you get to the brain during an operation?”
It was an important question, followed by a flurry of other questions from other classmates: (1) how does someone doing surgery actually remove part of a skull?; (2) if the skull is removed, is it put back (and if so, how?); (3) How does the skull and scalp heal, and what is visible from outside?; and (4) How does a neurosurgeon know exactly how much skull to remove, and where to remove it?
Dr.Ravish Patwardhan, who has seen, or himself performed, thousands of operations, elaborated: first, he asked the class exactly how we would know where the tumor (or whatever we were going after) was located. Someone in the class answered, “by looking at an MRI” – which was correct. Based upon a technique like a global positioning system for the brain, the patient’s head can be registered by computer to that patient’s MRI scan, and by touching that patient’s nose, for example, the computer would show an image touching the nose on the MRI scan. So, the tumor could be seen in three-dimensions on the MRI scanner while the operation was being performed, and a virtual pointer would appear on the computer MRI scan as well (even while the pointer were moved, showing what is actually underneath the scalp, in three dimensions). If this sounds too complex, then the simple way of deciding where to cut to make the initial incision can be figured out by measuring (again based upon the scan), how far to cut upwards from the nose, how many centimeters back from the ears and up towards the crown of the head, etc. In the older days, brain surgeons made much larger incisions, because then if they were “off” by a few centimeters, they could still access the tumor without removing more bone. Also, in the older days, they used a hand-held drill (which eventually was improved to stop when the bone was gone through, before it plunged into the brain, automatically by a mechanism), and then by making three or more holes and connecting them with a thin saw, a chunk of bone was removed (called a “bone flap”). Now, we use a high-speed drill to make the holes, and then connect these using a “footplate” attachment which has a flat edge protecting towards the brain side. The surgeon has to be careful, because this drill does not necessarily stop on its own, and control is needed. But the faster drill can do the procedure in a minute or so, which may have taken the saw ten minutes. The bone is removed after the scalp (the skin over the bone) is cut (usually in a curvy or straight line) and kept spread apart using a self-retaining instrument which holds it apart for the whole operation.
Once the bone is removed, the leathery lining of the brain, the “dura” (which is much thinner in older people) is seen. This is opened using a sharp pointed knife (called an 11-blade scalpel), and cut usually in an X-shaped fashion, revealing the deeper transparent layer called the arachnoid, and clear fluid usually comes out (called cerebrospinal fluid, which bathes the brain). The glistening brain becomes revealed (still a marvelous experience to see and behold, to consider what it stands for, according to Dr. Ravish Patwardhan, despite seeing it so many times in so many people). If the tumor is obvious, then it can be carefully dissected free and removed; if not, then again navigation (or measurement off an MRI scan) can be used to determine its location and the brain opened or lifted or separated in the specific location, to get access to this tumor. The way the tumor is approached is called (not surprisingly) “the approach.” So, neurosurgeons write books about “the skull base approaches” or the “frontal approaches” etc., to get to more challenging tumor locations.
After the tumor is removed (sometimes using a microscope covered with a sterile drape), the dura overlying it is stitched together using a suture, and then the bone is replaced using thin plates and screws (with the plates shaped like a “dog bone” with holes in each outer wider part, where tiny screws go. Several dog bone-shaped plates are used to secure a bone flap back to the skull. It will likely take years to heal and grow back, but if it doesn’t, claims Dr. Ravish Patwardhan, that’s not that important. Finally, the scalp is stitched back using sutures, and either stapled or sewn shut for the final thin skin layer.
After putting on an antibiotic ointment, putting on another dressing to the wound is optional – patients have healed fine in both cases, even with the incision otherwise exposed to air.
Remarkably, most of the brain feels absolutely no pain. So, operations like these (including drilling) can, and have been done on awake patients when it is critical to know that removing a brain tumor will not cause permanent paralysis or other such problem because of the important region of the brain next to it. The latest techniques, though, accomplish the same thing as a “craniotomy” described above, using little holes and endoscopes when possible, according to Dr. Ravish Patwardhan.
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