Endoscopy: The future of pituitary tumor treatment

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Advances in endoscopy, a decades-old technology, offers major advantages to patients with pituitary tumors by improved visualization, rehabilitation, and shorter hospitalization.

Dr. Newman

By Lynda Charters; Reviewed by Steven A. Newman, MD

Charlottesville, VA-Ophthalmologists should care about pituitary tumors because they are so common and they often involve the visual system, according to Steven Newman, MD.

Advances in endoscopy, he noted, offer major advantages to patients with pituitary tumors: improved visualization and rehabilitation and shorter hospitalization.

 “Involvement of the visual system in patients with pituitary tumors is not at all surprising since everything of interest to ophthalmologists passes by the area of the sella,” said Dr. Newman, professor of ophthalmology and neurological surgery, University of Virginia, Charlottesville, VA. “Lateral to the sella are the third, fourth, fifth, and sixth cranial nerves, and the optic nerve and the chiasm are above the sella.”

Early investigations by Harvey Cushing, MD, into pituitary tumors clearly recognized the presence of visual problems in these patients. Five classical syndromes were described that depended on the location of the chiasm in relation to the sella.

“With a post-placed chiasm, optic neuropathies are seen producing central scotomas and arcuate defects,” Dr. Newman said. “When the crossing fibers are involved, a junctional scotoma can be seen. When the chiasm is over the sella, a superior bitemporal defect is typical (the most common chiasmal syndrome).

“With a prefixed chiasm, posterior chiasmal pathology can occur with an inferior or scotomatous bitemporal defect, and in cases with a severely prefixed chiasm, a homonymous hemianopsia can occur due to tract involvement,” he added.

Evolving spectrum of pituitary tumors

From the mid-1950s to the early 1980s, the incidence rates of visual field defects and optic atrophy were seen to decrease substantially.

“The change in the clinical spectrum was related to the recognition of endocrine symptoms and the advent of neuro-imaging,” Dr. Newman noted. “Thus, there were an increasing number of patients without visual symptoms.”

Currently, the symptoms that are commonly seen are menstrual irregularities, galactorrhea, and loss of libido and impotence, and most ophthalmologists rarely ask these questions of patients. In spite of the increasing recognition of endocrine symptoms-and the added incidence of fortuitous pick-up when scans are done for other reasons-visual field defects, acuity loss, and diplopia still occur.

Dr. Newman recounted the results of a study of 200 patients reported from Montreal in 1981. In patients with secretory tumors, only 7% or less had visual field defects and the tumors were small (up to 16.7 mm) compared to patients with non-secretory tumors, 60% of whom had visual acuity defects and substantially larger tumors (33.8 mm on average).

Treatment

Bromocriptine (Parlodel, Novartis Healthcare) and its subsequent derivatives was a major medical treatment advancement that, according to Dr. Newman, has changed the paradigm of care for patients with prolactinomas. Octreotide acetate (Sandostatin, Novartis Pharmaceuticals) may also shrink tumors in patients with acromegaly. Radiation therapy has been applied since the late 1890s, first fractionated and later non-fractionated (Gamma Knife radiosurgery).

Despite these advances in treatment options, most patients still are candidates for surgical decompression (transphenoidal and transcranial). The development of skull-base surgery has resulted in improved image guidance and better hemostatic agents.

Endoscopy

Endoscopy was developed more than 200 years ago, but became practical in the 1960s with introduction of a cold light source.

“Endoscopy offers an unparalleled wide-angle view of the skull base, avoids brain retraction, facilitates tumor devascularization at an early stage, and leaves no visible scars,” Dr. Newman said.

The indications for neurosurgical endoscopic resection include pituitary tumors, craniopharyngioma, and other intrasellar pathologies. The indications also have been extended to include tuberculum meningiomas and clival lesions.

A total of 824 patients have undergone endoscopic resections at the University of Virginia, including 381 patients with nonfunctioning pituitary adenomas.

As with all techniques, endoscopy has its limitation, such as cavernous sinus extension especially lateral to the carotid artery, vascular involvement, and superolateral extension, Dr. Newman said.

Likely future advances include the use of 3-dimensional stereopsis-available now-and robotics.

“This may become as simple as femtosecond laser,” he said.

“While there has been a changing spectrum in pituitary tumors with the emphasis on sexual dysfunction and headache, evaluation of the visual field is still as important as it was in 1835 when William MacKenzie first postulated that a bitemporal defect indicated pathology at the area of the chiasm,” Dr. Newman explained. “Endocrine evaluation is critically important for patients with prolactin-secreting tumors, who should not immediately go to a neurosurgeon.

“Endoscopy offers major advantages, such as better visualization, shorter hospitalization, and better rehabilitation. This is truly an evolving technology,” Dr. Newman concluded.

Steven A. Newman, MD

E: SAN7A@hscmail.mcc.virginia.edu

Dr. Newman has no financial interest in any aspect of this report.