Question: Some Cushing’s patients have found that their insurance companies will not refer them to an “expert” pituitary surgeon. Why is an expert pituitary surgeon necessary?
While there are no literature references that state exact percentages, the cure rate for pituitary tumors is directly related to the experience of the surgeon. Neurosurgery is a broad field that includes surgery on the brain, the pituitary gland, and the spine. In general, greater than 70% of the procedures done by neurosurgeons are on the spine, with an occasional brain or pituitary procedure. The greater cure rate obtained by an experienced pituitary surgeon stems from technical repetition of the procedure, which yields a greater appreciation for subtle changes in the physical appearance of tumor tissue, as well as superior mobilization of the gland to discover all of a tumor. In general, a neurosurgeon that performs 1 pituitary surgery every other week, or between 20-25 such surgeries a year, should be proficient in the procedure. The pituitary surgeon need not be a “Cushing’s tumor expert”, as ACTH secreting pituitary tumors account for only about 15% of all pituitary tumors. From a surgical perspective, the techniques employed and the skills required are the same for all transsphenoidal pituitary surgeries. There are situations, such as Nelson’s, where consultation with a very experienced pituitary surgeon who has done thousands of pituitary surgeries may be warranted.
Question: How long has the trans-sphenoidal surgical approach been the preferred surgical method and what does it entail?
The modern era of trans-sphenoidal surgery dates to the early 1960′s (the procedure was actually first described in 1904). The advent of this procedure made a dramatic difference in the treatment of pituitary tumors.
In general, the procedure involves an incision in the upper gum, which allows access to the pituitary gland with specialized instruments. The surgeon then views the area to determine the location of the tumor. In cases of small tumors, the tumor is removed, leaving the pituitary gland primarily intact. Only when the tumor has spread thoughout the entire gland, is the removal of the entire pituitary necessary. This rarely happens with ACTH secreting tumors, as they are usually small enough that the tumor can be removed without removing the pituitary. In general, most transsphenoidal procedures take about 2 1/2 hours.
After surgery, patients are most usually kept in intensive care for at least one night so that blood pressure, heart rate, and replacement medications can be continuously monitored. The patient then spends approximately another 3 days in a surgical care unit before going home. Following surgery, patients will have packing in their nasal cavity for a day or so; it is not uncommon for patients to experience increased thirst and to have some headache (usually resolved by Tylenol) while the packs are in place. Most patients are walking and eating mostly normal foods within a few days.
Question: What is the determining factor in whether all of a pituitary tumor can be removed?
Tumors vary in their size and invasiveness. The most common reason that a tumor cannot be completely removed, is that it has invaded adjacent structures such as the cavernous sinus, or the dura or bone of the sella that surrounds the pituitary. Often times, such invasion cannot be adequately visualized on an MRI, and the full extent of invasion is not known until observed during surgery.
Tumors are catagorized according to their size and invasiveness. The rating scale I use is the Hardy scale, which ranks tumors from Stage I to Stage IV, Stage I being the smallest and least invasive. In Stage I tumors, those less than 1 cm in size with no invasion, our statistics reveal that 91% of these tumors can be successfully removed completely. In contrast, stage 4 tumors, that are larger than 1 cm in size and show diffuse invasion, can be completely removed less than 10% of the cases.
Cushing’s tumors tend to be smaller (Stage I or II) perhaps because patients become symptomatic before these tumors have an opportunity to become extremely large. Because of the tiny size of tumors frequently seen in Cushing’s disease, the tumors are not always visible on an MRI, and very few effect the optic nerve. Early diagnosis, while the tumor is still small, is important to maximize the opportunities for a full recovery.
Question: What is the treatment of choice for Nelson’s syndrome?
Nelson’s tumors are difficult tumors to manage. If the tumor is localized to the pituitary, another transphenoidal resection may be in order. Dr. Ed Oldfield, of NIH, has published results from multiple transsphenoidal surgeries and these results indicate, that if the tumor can be visualized, it is worth trying the procedure again. If the tumor is not localized to the pituitary gland, but rather has invaded adjacent structures, removal of the entire pituitary will not result in a cure. Nelson’s is a case where the patient should see a very experienced neurosurgeon in a facility that has access to the latest radiation technology. The newer stereotaxic radiation therapies are often carried out by neurosurgeons, as the procedure is very focused to a particular area, and can be viewed as a surgery. The most common kinds of stereotaxic radiation include Gamma Knife, Proton Beam, and Linac. There are differences between these that make one technique perferable over another, depending on the specific tumor.
Author: Dr. Martin Weiss MD (Spring, 1997)
Editor’s Note: Dr. Weiss is Professor & Chairman of the Department of Neurosurgery at the University of Southern California. He has been Chairman of the American Board of Neurosurgery, The Residency Review Committee for Neurosurgery, and the Editorial Board of The Journal of Neurosurgery. He has also served as VicePpresident of the American Academy of Neurosurgery and the Congress of Neurological Surgeons, Secretary of the American Association of Neurological Surgeons and has been Associate Editor of The Journal of Neurosurgey.