"Glitches" Discovered And Fixed In Animal Study Make Surgery For Human Pituitary Tumors Quicker, Safer And Less Painful

The animal study that led to the safe use of the technique in human surgery appears in the April issue of the 'Journal of Laparoendoscopic and Advanced Surgical Techniques.'

The pituitary gland, about the size of a pea and located beneath the brain and behind the nose, produces a variety of hormones and controls most of the hormones in the body. It is situated in a cup-like area of the skull called the sella turcica, behind and above the sphenoid bone.

To remove tumors of the pituitary, surgeons historically have reached the gland by making a hole in the front of the skull or going through the sphenoid bone at the base of the skull. Although the 'transcranial' approach is still sometimes used to remove large tumors, the 'transphenoidal' technique is far more common today.

Surgeons typically make an incision under the upper lip or under a nostril, then use surgical tools to clear a path to and through the sphenoid bone and up to the sella turcica. Once there, they use a high-powered surgical microscope to view the tumor and use microsurgical tools to dissect and remove it.

The introduction and evolution of surgical microscopy over the past several decades has given surgeons a close-up, detailed view of their work. But Hrayr Shahinian, M.D., director of the Skull Base Institute, has found that an endoscopic telescope offers a much better look at the entire area.

Switching between two lenses of different angles, the endoscope can be manipulated to provide a view of the spaces around the gland to reveal residual tumor that otherwise might not be detected. The telescopes also give better definition of the relationships between the pituitary and surrounding structures. Furthermore, because the telescope's tube is smaller in diameter than a microscope's, surgeons may leave more tissue and bone intact. In fact, instead of cutting through the tissues of the mouth and nose, Dr. Shahinian and his team approach the sphenoid bone directly through a nostril and the nasal passages.

"We put a 2.7 millimeter telescope into the nostril and take the tumor out through the nose," he said. "There are no incisions, no scars, and the duration of surgery is shortened because we don't have to do the full approach anymore. There are fewer complications and patients go home the next morning. I have no doubt that within the next five years, this will be the method of choice."

In comparison, because of the larger incisions, greater trauma and increased risk of intranasal complications, patients who have undergone microscopic surgery generally have their noses packed with gauze for several days and remain in the hospital for about five days.

"About three years ago, I was doing all of these surgeries with the microscope," said Dr. Shahinian. "Then I started taking an endoscope and, after doing the procedure with a microscope, I'd insert the endoscope to look around corners. Then I thought, 'Why am I doing all the approach, all the big dissection with the microscope and then putting the endoscope in? Why can't I just do it with an endoscope, period?'"

To be sure the new procedure would be safe, Dr. Shahinian's team, assisted by veterinarians, attempted to remove the pituitary glands of two pigs using the telescopes alone. Pigs were chosen as subjects because their skulls are anatomically similar to those of humans.

"Our experiment was conceived to demonstrate two principles," said Dr. Shahinian. "First, we wanted to show that we could gain access to and adequately expose the sphenoid sinus completely transnasally. In other words, we wanted to show that we could reach the space housing the pituitary gland through the nasal passages, without the need for incisions in the mouth or nose. Second, we hoped to document our claim that the areas around the pituitary could be better visualized with the telescope than with the microscope."

The researchers encountered several unexpected problems. First, because of the length of the pigs' snouts, the telescope was not long enough to extend to the back of the nasal cavities. Dr. Shahinian improvised by making an incision in the roof of the mouth. This was considered only a minor setback because endoscopic surgical experience in human nasal passages is commonplace and well-documented.

Once the telescopes were positioned, two additional hurdles were realized. The doctors found that holding the operating equipment in one hand and manipulating the telescope with the other tended to be cumbersome at times. Also, placement of the endoscope's lens into the surgical site exposed it to fluid and debris, which obscured the view and required frequent removal, cleaning and replacement of the scope.

Both of these problems have since been overcome. A holding arm is now available to lock the telescope in place, freeing both hands for manipulation of surgical instruments, and an irrigation system is used to keep the lens clear.

Performing the procedure on the pigs, which were anesthetized during the surgery and later humanely euthanized by the veterinary staff, allowed Dr. Shahinian's team to 'fix the glitches' before bringing the technique into the operating room. Since completing the experiment and remedying the problems, which took place about a year ago, he has used the endoscopic technique exclusively.

Before founding the Skull Base Institute in 1996, Dr. Shahinian trained in general surgery, plastic surgery, microsurgery,craniofacial surgery and skull base surgery. This 'hybrid' education provides him with a unique set of skills that is perfectly suited to treating pituitary tumors and other disorders that commonly occur at the base of the skull.