What To Do With a Pituitary Adenoma

Pituitary adenomas are benign, slow-growing neoplasms that account for 10% to 15% of intracranial masses, making them the most common type of pituitary disorder.¹ The highest incidence of pituitary adenomas occurs in patients 65 to 84 years of age.² Pituitary adenomas can be categorized as functioning (ie, hormone secreting) or non-functioning (ie, nonhormone secreting). An adenoma less than 10 cm in size is referred to as a microadenoma, and those larger than 10 cm are known as macroadenomas.

This article details a case of a patient who was diagnosed with a pituitary macroadenoma after his visual symptoms and ocular examination findings prompted neurologic evaluation.

CASE REPORT

A 61-year-old White man presented with the complaint of a gradual bilateral decline in vision and loss of peripheral vision over the past 6 months. He also reported persistent headaches over the same time frame. His medical history was positive for chronic obstructive lung disease, hyperlipidemia, and depression. He used an inhaler as needed and reported an allergy to perfume. His ocular history included cataracts, presbyopia, and compound hyperopic astigmatism; his family ocular history was negative.

On examination, the patient’s BCVA was 20/100-2 OU. Refraction yielded +1.25 -100 x 075º (20/100-2) OD and +1.75 D sphere (20/100-2) OS. His confrontation fields showed superior constriction, normal pupils, and full motilities. The anterior segment of each eye was unremarkable, and his IOP was 15 mm Hg OU. His optic nerves had distinct margins with no atrophy or pallor, his cup-to-disc ratios measured 0.30 round, and the remainder of each posterior segment was unremarkable. Same-day visual field testing revealed a bitemporal hemianopia. On OCT, his retinal nerve fiber layer (RNFL) showed borderline thinning inferiorly in each eye. His ganglion cell complex was within normal limits (360º OU).

FURTHER TESTING

The patient was promptly referred to neurology due to the concern of a pituitary adenoma. A noncontrast head CT scan revealed a 3.2 x 2.3 x 2.3-cm sellar mass with suprasellar extension on the undersurface of the optic chiasm. A brain MRI with contrast was subsequently ordered, which confirmed a pituitary macroadenoma, and the patient was referred to a neurosurgeon for further management.

The neurosurgeon used a transsphenoidal endoscopic approach to surgically remove the pituitary macroadenoma, and the patient followed up at the eye clinic 6 months later. At this visit, he reported resolution of his headaches and noted an improvement in both his visual acuity and visual fields. His visual acuity had improved to 20/25-2 OU with refraction remaining stable. His confrontation fields, which previously showed superior constriction in each eye, were now full. The patient’s pupils were normal, motilities were full, and the anterior and posterior segments remained stable. On visual field testing, it was noted that the bitemporal hemianopia had resolved without any residual visual field deficits. Additionally, the patient’s OCT RNFL and ganglion cell complex scans had remained stable from his prior visit.

SIGNS AND SYMPTOMS TO KNOW

Some patients with a pituitary adenoma are asymptomatic, and associated findings may be caught incidentally during a routine eye examination. Common signs and symptoms of a pituitary adenoma include headaches, hypopituitarism, afferent pupillary defect, visual field defects, ophthalmoplegia, reduced stereopsis, and dyschromatopsia. Headaches do not have a correlation with tumor size, whereas visual changes have shown a positive correlation with tumor size.^3,4 Visual disturbances, particularly visual field defects, are the most common symptom at presentation,⁵ with bitemporal hemianopsias presenting in 46% of patients due to direct and inferior compression of the optic chiasm. Junctional scotomas, centrocecal defects, incongruous hemianopsias monocular defects, and mixed visual defects may also occur, depending on the location of the pituitary adenoma.⁶ Binocular diplopia may occur due to paresis of cranial nerve III, IV, or VI as a result of lateral extension of the tumor into the cavernous sinus.⁷ The diplopia may have horizontal, vertical, or torsional components, depending on the combination of cranial nerves affected.

Pendular seesaw nystagmus is a rare form of nystagmus characterized by cyclical, pendular eye movements, where one eye elevates and intorts, while the other eye is depressed and extorts. This condition is pathognomonic for parasellar/suprasellar masses.⁸ Patients with a bitemporal visual field defect will not have a relatively afferent pupillary defect; however, a relatively afferent pupillary defect will be present if there is significant asymmetry of visual field loss. Optic atrophy is representative of chronic compressive damage. If only the fibers nasal to the macula are damaged, the nasal and temporal aspects of the nerve will appear atrophic and display a “band-shaped” pattern, likely due to compression of the optic tract.⁹

Similarly, when assessing the RNFL weeks to months after the damage occurs, binasal macular ganglion cell atrophy will correlate with temporal and nasal RNFL atrophy, sparing the superior and inferior quadrants. This creates a classic bowtie or band-shaped appearance of RNFL thinning.¹⁰

MRI with and without contrast of the brain and orbits may confirm a suspected diagnosis. MRI postcontrast coronal sections are most helpful in identifying any extension of the adenoma into adjacent structures. MRI can also indicate if a pituitary apoplexy is present, which is caused by an infection or a hemorrhage of the pituitary gland, often involving a preexisting pituitary adenoma. This condition may cause severe, sudden headache and can be life-threatening if not treated immediately.

MANAGEMENT

Once a diagnosis is confirmed, the patient will need to be comanaged with neurology, neurosurgery, and endocrinology. Treatment for pituitary adenomas may range from dopamine agonists to gamma-knife radiotherapy or endoscopic or microscopic transsphenoidal surgery. Although microadenomas respond well to treatment and tend to have a favorable prognosis,¹¹ macroadenomas that are invasive or hormone-producing may have a less favorable prognosis and a higher risk of recurrence.¹² Systemic health factors, such as hypertension, diabetes, or cardiovascular conditions, may also influence the prognosis of pituitary adenoma.¹³ Tumor size is not significantly associated with postoperative vision/visual field defect recovery but rather a shorter duration of symptoms, younger age, and better preoperative BCVA.¹⁴

Following treatment, it is recommended to monitor patients at 3- to 12-month intervals for any visual changes and potential recurrence.¹⁵

PREPARE FOR A RANGE OF PRESENTATIONS

Pituitary adenomas are relatively common benign tumors that optometrists may frequently encounter. Some patients are asymptomatic, whereas others may report symptoms such as vision loss and/or loss of peripheral vision. The prognosis of a pituitary adenoma is generally favorable, especially if diagnosed early. Understanding the signs and symptoms patients may present with can aid in appropriate team management and, ultimately, support an optimal outcome.