Sometimes the things we don’t do are just as important as the things we do. Did you almost marry the wrong person? Or make a conscious decision not to go into debt for college? Those might have been difficult decisions at the time, but in retrospect you’re likely glad about those “didn’t do’s.”
Neurosurgery is similar. While the neurosurgeon is tasked with “doing” something, such as removing a tumor, much of what he doesn’t do during surgery has a substantial impact on the patient. The neurosurgeon must take precautions that prevent bleeding and infection. He must also be aware of the long-term effects brain surgery can have on the patient’s life. The neurosurgeon must determine the best way to balance the risk of incompletely correcting the disease with the risk of damaging surrounding brain tissue.
In the case of meningiomas located in the cerebellopontine angle, this is particularly true. Let’s break that down before we look at the “doing” and the “not doing.”
Meningiomas are benign (non-cancerous) tumors that affect the membrane surrounding the brain.
The cerebellopontine angle (CPA) is the area between two important structures—the cerebellum and the pons—in the back of the brain. Several important structures pass through the CPA, including the facial nerve.
The facial nerve, also known as Cranial Nerve VII, arises from the brainstem, or the rear portion of the brain that connects to the spinal cord, and travels through the CPA to the muscles of the face. The facial nerve is responsible for our ability to smile, frown and look surprised. It also gives us much of our ability to taste.
Balancing the “do” of removing a meningioma in the CPA and the “don’t” of damaging the facial nerve requires experience and keen judgment on the part of the surgeon. If he pushes too hard to remove the entire tumor, the facial nerve may be damaged. This can result in disabling and disfiguring facial paralysis. But he must consider whether a second surgery will be required if he leaves some tumor behind and it continues to grow.
Dr. Michael Sisti from Columbia University Medical Center/NewYork-Presbyterian Hospital has been treating CPA meningiomas for more than a quarter century, and the results of his experience are the focus of the cover article in the December issue of the Journal of Neurosurgery. The journal cover features an artist’s representation of surgical treatment of CPA meningioma.
Primary authors of the study include Dr. Randy D’Amico and Dr. Matei Banu, both neurosurgical residents at Columbia University Medical Center. Dr. Hani Malone, former Chief Resident and graduate of the Columbia Neurosurgical Residency program, contributed to the research, with Dr. Sisti serving as senior author.
Researchers reviewed the techniques and outcomes of each of Dr. Sisti’s surgeries on CPA meningiomas from 1992 to 2016. They evaluated several factors, hoping to identify guiding principles going forward in the treatment of these tumors. These factors included initial tumor size, the site of origin of the tumor, symptoms and the patient’s health status. The researchers then compared the treatment choices with tumor regrowth and facial nerve damage after surgery.
This wasn’t the first time Dr. Sisti used these characteristics to determine how best to treat a complicated tumor. A similar series of patients with acoustic neuromas (tumors that affect the nerve responsible for transmitting information about sound and equilibrium) was followed for 11 years, and the results published in the Journal of Neurosurgery in 2011. The excellent results from this study helped guide Dr. Sisti in his treatment of CPA meningiomas.
Dr. Sisti used the size of the CPA meningioma to choose the type of surgery to perform. For tumors smaller than 2.5 cm, he used Gamma Knife radiosurgery, which, contrary to its name, doesn’t involve a knife. Instead, it uses focused radiation to destroy the tumor.
For larger tumors, Dr. Sisti used microsurgical resection. This means miniature surgical instruments and a microscope were used to perform a very precise removal of the tumor. While this surgery is microscopic, it is still a surgery that requires opening the skull to access the tumor, and carries its own set of risks. Because of these risks, which include infection and bleeding, surgeons prefer to pursue nonsurgical treatments when appropriate to minimize such complications.
Of the patients who were studied, those who underwent Gamma Knife radiosurgery for the smaller tumors had no cases of tumor regrowth and minimal facial nerve complications.
The study also suggests that it is reasonable to use microsurgical resection for larger tumors without removing the entire tumor. In these cases the surgeon selectively leaves behind certain portions of the tumor, avoiding facial nerve complications for the patient. As Dr. Sisti explains, “The tumors are benign. They don’t necessarily always grow back. But the ones that do would be small enough to be treated easily, nonsurgically, with Gamma Knife.”
While radiosurgery is not typically used to treat the larger tumors because of the risk of additional radiation associated with using the treatment in a large area, it is suitable to address small recurrences. This more conservative approach limits the future need for a second open brain surgery. At the same time it minimizes the chances of facial nerve damage or radiation toxicity.
Neurosurgeons must sometimes rely on their best judgment and personal experience to determine how to proceed with a particular surgery because data can be limited for unusual diseases. This review of a 24-year series of patients fills in the blanks for neurosurgeons around the world as they decide what to do—and what not to do—in their treatment of CPA meningiomas.
Listen to Dr. Sisti discuss this research and inspiration for the JNS cover in the clip below:
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