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NEW TECHNOLOGIES JOINING FORCES TO TREAT PITUITARY TUMORS

From Washington University Physicians, posted July 2, 2010, written by Mary Jo Blackwood, RN, MPH

The pituitary gland, about the size and shape of a kidney bean, sits at the base of the brain and generates hormones that affect growth and the function of other glands in the body. Adenomas, generally benign tumors, can arise from the pituitary gland, causing excesses or deficiencies in hormone production that create systemic problems. Other pituitary adenomas secrete no measurable amount of hormones, but can cause vision loss and other problems from direct compression.

Cushing’s disease is caused by excessive production of a hormone (ACTH) by certain pituitary tumors and can result in excess deposits of fat in the face, back and chest, as well as hypertension, diabetes, poor healing, easy bruising and many other serious medical problems.

Acromegaly results from pituitary tumors secreting excessive amounts of growth hormone, resulting in tall stature, enlargement of the hands, feet, tongue and facial features, even enlargement of the heart.

Removing the tumor is often the best solution for many patients, but other options including observation, treatment with medications, or even various types of radiation such as Gamma Knifetm radiosurgery may be appropriate depending upon the circumstances.

Washington University neurosurgeon, Michael Chicoine, M.D., says his options for attacking these tumors have become better and better. Not only does he have access to amazing technology, but the support of treatment collaborators in other disciplines: endocrinologists on the hormonal issues, and otolaryngologists (ENTs) during tumor removal surgery. “Our otolaryngology colleagues have long used endoscopy to do sinus surgery. Now we’re applying what they’ve learned to tumor resection on the pituitary and other skull base tumors. We found we could use the endoscope to reach pituitary tumors through the nose or beneath the upper lip less invasively and without any external incisions.”

Endoscopy

An endoscope is made up of a rigid or flexible tube with a fiber optic light to illuminate the organ, and a lens system that transmits the image to the viewer from the fiberscope to a video monitor. The endoscope may be placed in one nostril to illuminate and visualize the tumor, while other surgical instruments are placed in the other nostril to remove the tumor Chicoine hastens to add that this is not your father’s endoscopy. Earlier versions had analog video. Today’s displays are produced by high-definition cameras and viewed on large flat panel monitors, and may even employ three-dimensional technology. Surgeons less commonly access tumors through the traditional incision beneath the upper lip but instead go deep into nasal passageways, removing a small amount of cartilage, bone and mucosa from the sinuses to reach the tumor.

Intraoperative MRI (iMRI)

MRI (magnetic resonance imaging) allows neurosurgeons to see the difference between healthy and diseased brain tissue. In most operating rooms, neurosurgeons do the best they can to remove the pituitary tumor using traditional surgical techniques. Then, after surgery, the patient may have another MRI to determine how successful they were and whether there is more tumor that needs to be removed or perhaps treated with other approaches.

Barnes-Jewish Hospital was one of the first hospitals in the world to introduce high field strength intraoperative MRI (iMRI) with a movable magnet, allowing the neurosurgeons to see MRI images during surgery and more completely remove tumors while the patient is still asleep. Says Chicoine, “We have two specially designed adjacent operating rooms that use the iMRI, so two surgeons can be doing procedures at the same time. The magnet is mounted on a ceiling track and can slide in an out of each room with the touch of a remote, even though it weighs about six tons, allowing it to be used in either room as needed. The rooms are larger than conventional operating rooms to allow for this. Magnetic field sizes marked on the floor allow us to move all metal objects out to the periphery during imaging so they don’t become projectiles. All anesthesia and EKG equipment used in these two rooms are MRI-compatible.”

Not only does the patient benefit from the iMRI in more complete tumor resection, but the endoscopy and MRI images and other data can be combined on high resolution flat screen monitors so surgeons always know where they are. An intra-operative surgical navigation device (akin to a GPS positioning system) uses pre-operative MRI scans to map the anatomy of the head for navigation during surgery. Further scans during surgery can be integrated to update the map as pituitary tumor mass is removed.

Gamma Knife™

Some pituitary tumors cannot be completely removed because of their proximity to sensitive structures, like the carotid artery. After the surgeon has removed as much of the tumor as possible, the patient recovers, and typically returns home within 2 to 5 days. In the weeks and months thereafter, follow-up MRIs are obtained. If significant residual or regrowth of tumor is identified, the patient may be referred to a radiation oncologist for future evaluation. In radiation oncology, the neurosurgeon works with a radiation oncologist to target the remaining tumor with a high intensity radiation treatment, called Gamma Knife radiosurgery, a one-day outpatient non-invasive procedure that derives its name from its ability to deliver radiation to a tumor with surgical precision.

While patients with pituitary tumors clearly benefit from these multidisciplinary collaborations and state of the art technologies, that benefit extends to other many other types of tumors of the brain and skull-base as well as non-tumor conditions, as well. Says Chicoine, “While we originally focused on pituitary tumors with the advanced endoscopic techniques, we now know we can treat other non-cancerous conditions such as meningiomas, cerebral spinal fluid leaks, and various types of cysts.”
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Copyright 2010 Washington University School of Medicine
Copyright 2010 Washington University School of Medicine