Deep in the brain
The bottom of the human brain is a busy, chaotic place. The brain rests on the floor of the skull, which has many openings. Through these various portals pass the spinal cord—the bundle of nerves that manages the body’s every movement and mechanism—as well as blood vessels that keep the brain nourished. Treating a tumor that arises in this dense thicket of tissue at the base of the skull is a delicate, daunting challenge.
“You can’t simply move the brain out of the way,” said Nicholas Coppa, MD, FAANS, a neurological surgeon at Cape Cod Hospital.
Accessing the tumor is challenging, but fortunately, Dr. Coppa and other surgeons who specialize in skull base surgery have answers to the question of how to remove tumors and other unhealthy growths that form deep in the cranium. Before coming to Cape Cod Hospital in 2013, Dr. Coppa was an assistant professor of neurological surgery at Oregon Health and Science University (OHSU) in Portland, Oregon. At OHSU, he completed a one-year fellowship (or advanced training) in skull base and cerebrovascular neurosurgery and neuro-oncology surgery, then spent the next four years performing these complex cranial operations.
The techniques used in skull base surgery allow doctors to treat a variety of diseases that strike in hard-to-reach recesses of the cranium. Some tumors that form at the base of the skull are cancerous, or malignant, though many are noncancerous, or benign. That doesn’t mean the latter are harmless, however. For example, meningiomas are a common type of tumor that forms in the membrane of the brain, including at the base of the skull. About 90 percent of meningiomas are benign, but left untreated they can grow and impair brain activity, causing disability and even death.
Likewise, formations called epidermoid brain cysts are usually benign, but can cause symptoms such as hearing loss, headaches and facial twitching. Clusters of abnormal blood vessels known as cavernomas can form in the skull base, too, with the potential to cause seizures, hemorrhages and stroke symptoms.
Different Strategies Used
To treat most brain tumors, surgeons perform a craniotomy, which is the removal of a portion of bone from the skull. But to access deep-seated tumors and other abnormalities, doctors trained in skull base surgery use different strategies, approaching them with minimally invasive methods that take advantage of natural passages in the cranium. Using fine drills and other instruments, surgeons may enter through the posterior fossa, at the back of the neck, for example, or the temporal bone, behind the ear. Or, in some cases, through the nose. That’s the pathway used in certain operations, including a procedure called endoscopic endonasal transsphenoidal surgery, which is performed to remove tumors that develop on the pituitary gland. This pea-sized organ produces various hormones and is located at the base of the brain, at about eye level.
Most tumors that form on the pituitary gland are benign but, when they grow large enough, are capable of causing symptoms that include headaches and visual problems, such as double vision or loss of peripheral vision. Moreover, said Dr. Coppa, “these tumors can be locally aggressive, meaning that they tend to recur in that area and be a problem.”
To treat these and similar tumors, Dr. Coppa and other neurological surgeons at Cape Cod Hospital collaborate with their colleagues in the department of otolaryngology services, who specialize in treatment of disorders of the ear, nose and throat. After the patient has been placed under general anesthesia, the surgeon inserts small surgical instruments into the sinus cavity and removes a small amount of bone and soft tissue to create an opening in the base of the skull, allowing access to the tumor.
To guide his instruments, Dr. Coppa inserts an endoscope, a thin tube with a camera and light on the tip, into the sinus cavity. The endoscope is directed to the site of the tumor, projecting images onto a TV monitor. For many years the standard method for performing this procedure was to insert a slender cylinder called a retractor into the sinus cavity. Surgical instruments were manipulated through the retractor, which the surgeon peered down with a microscope to view the tumor and gland.
New Gold Standard
Dr. Coppa was trained with this technique, but recently transitioned to the newer endoscopic approach.
“In my opinion, it’s becoming the new gold standard. The visualization (of the tumor) is a lot better—it’s more panoramic.”
To remove the tumor (which Dr. Coppa noted has the consistency of cottage cheese), a surgeon uses a scraping tool called a curette and a suction device. Using the endoscopic technique allows for more tumor removal, he said. Another advantage of the endoscopic method is that a surgeon can check his or her work at the end of the procedure.
“I can actually put my camera right in there and see for myself whether the tumor is out,” he said.
In many communities across the United States, patients who have pituitary tumors and other abnormalities at the base of the skull must travel to academic medical centers to be diagnosed and treated. With the expertise and experience Dr. Coppa and his colleagues bring to the operating table, it’s possible for Cape Codders unfortunate enough to develop one of these relatively rare conditions to receive top-quality care close to home.