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CASE REPORT You may be the first to spot visual field defectsand other signs of pituitary adenomas. Appropriate follow-up testing and timely referral saved this patient's vision. by Andrew S.
Gurwood, O.D., Adrienne B. Ari, O.D., and Elena C. Golde, O.D., Philadelphia A 63-year-old black female presented complaining of periodic dizziness and blurred vision. She said she had those symptoms for about two months.
Her medical history included high cholesterol, which she controlled by diet, and seasonal sinusitis. Her family history was non- contributory, and she denied taking any medications. Diagnostic Data
Biomicroscopy revealed healthy external structures and open angles. Intraocular pressure was 16mm Hg in each eye. Dilated fundus examination revealed temporal pallor of both optic nerve heads. We noted two dot hemorrhages with adjacent lipid flecks in the juxtapapillary region of the left eye. An automated central 24-2 threshold visual field demonstrated a non-congruous bitemporal quadrantnopsia. This was more dense superiorly, and the left eye was more involved than the right. We referred the patient for an MRI, chest X-ray and blood work, including a two-hour post-prandial blood sugar, complete blood count with differential and fluorescent treponemal antibody absorption test. Diagnosis Treatment and Follow-up We saw the patient again at two weeks post-op. At this exam, her visual acuity and extraocular muscle movements were normal, and confrontation fields were full. As she recovers, our clinic comanages her care with the neurosurgeon.
Pituitary adenomas are typically slow-growing, benign neoplasms. They usually arise from the adenohypophysis (the anterior lobe of the pituitary gland), and may cause patients to experience systemic and visual signs and symptoms.1-13 Pituitary adenomas represent 10 to 15 percent of symptomatic neoplasms.10,14,15 Interestingly, 6-23 percent of all pituitary glands examined during autopsy reveal some evidence of neoplasm, speaking to its characteristic slow growth rate and often uneventful course.10,14,15 Joel Glaser went so far as to generalize that approximately one in 10 people died with a prolactin-secreting pituitary adenoma without symptoms.10 Pituitary adenomas usually present during early adulthood, and equally affect both sexes. There are no outstanding reported risk factors.1 However, nonsecreting adenomas, which this patient had, present later in life—average age 57—and occur more often in men.10,14,15 The tumors are differentiated by: • Secreting vs. non-secreting. Endocrine-active, or secreting, tumors include prolactin-secreting adenomas, growth hormone-secreting adenomas, thyroid-stimulating hormone adenomas, adrenocorticotropin hormone adenomas and multiple hormone adenomas.10,14,15 Nonsecreting adenomas make up 25 percent of pituitary tumors and are usually found to be larger than their secretory counterparts.10,14,15 Adenomas known not to secrete include inactive onocytoma, null cell tumors, prolactin tumors without galactorrhea (spontaneous flow of milk from the breast in women) and "low hormone" adenomas.10,14,15 Internal medicine doctors typically detect secreting adenomas before eye-care specialists, because patients are more likely to present to them first with a pertinent systemic symptom. Optometrists diagnose pituitary adenomas first when they produce visual symptoms. • Size. Microadenomas, which measure up to 1cm in diameter, have little impact on the visual system or gland function.1-10 Macroadenomas measure larger than 1cm, and present with mass-effect symptoms such as headache.1-10 Macroadenomas include non-secreting adenomas, prolactin-secreting adenomas and growth hormone-secreting tumors.1-10 • Effects. Hormonal disturbances result when hyper or hypo secretions occur. Prolactinomas, the most common form of pituitary tumor, cause amenorrhea (the loss of menstruation), galactorrhea and infertility in females, and hypogonadism (inadequate gonadal function), decreased libido and impo- tence in males.4-6,8 Tumors that secrete excess growth hormone cause gigantism in children and acromegaly in adults.2,8 Other symptoms include chronic frontal headaches, fatigue, thyroid changes and sexual hair changes. Since most secreting adenomas are small, visual symptoms may be delayed for years. Mechanical disturbances result when the tumor compresses adjacent structures. When pituitary tumors reach 10mm or more, they impinge on the optic chiasm, which is located 8-13mm above the pituitary gland. This produces the telltale bitemporal hemianopsia with increased superior density.2,4-6,8 The tumor usually grows asymmetrically, so the field loss between the two eyes tends to be asymmetrical.4,6 In rare instances the anterior aspect of one nerve produces a painless, ipsilateral central scotoma. Pituitary adenomas are the most common compressive pathology to affect the optic chiasm. Other compressive pathologies include craniopharyngiomas, supersellar meningioma and gliomas. Less common compressive lesions include aneurysms, arachnoidal and epithelial cysts, and mucoceles.
Besides bitemporal field loss, patients with pituitary adenomas might present with headache, blurred vision or these ocular signs: • Visual acuity loss . When a pituitary tumor interrupts visual acuity and the visual field, the patterns are specific and limited in their variation. In some cases the patient loses enough acuity and field that the eyes inadvertently move into their phoric position. With exophoria (producing a crossed diplopia projection), images in the temporal fields slide together. These images create the visual illusion that objects are incomplete, broken horizontally or misaligned vertically— the hemifield slide phenomenon. • Paretic or non-paretic extraocular muscle (EOM) palsy. This may occur if the tumor expands into the cavernous sinus.1-13 • Optic atrophy. Primary optic atrophy secondary to retrograde axonal degeneration is a sign of long-standing chiasmal compression.12,13 Severe optic atrophy may indicate poor visual recovery following surgical decompression.12,13 Differential diagnosis of pituitary tumor includes craniopharyngioma, meningioma and glioma. Craniopharyngioma are slow-growing tumors that arise from vestigial rem- nants of Rathke's pouch.1-13 Meningiomas are common, benign, slow-growing neoplasms that arise in the optic nerve sheath and are sometimes associated with neurofibromatosis.10,14,15 Gliomas are mostly benign, slow-growing pilocystic astrocytomas that arise from the supportive astrocytes of the optic nerve.10,14,15 These are associated with neurofibromatosis. Masqueraders of pituitary adenoma include chronic retrobulbar optic neuritis, nutritional amblyopia, uncorrected refractive error, low-tension glaucoma and age-related maculopathy.1-7 Misdiagnosis often occurs due to inadequate history, failure to correlate systemic signs and visual symptoms, or failure to perform adequate testing or follow-up.2 Perimetry, color testing and brightness comparison are important tools for diagnosing and locating neurologically based lesions.1-7 In this case, confrontation fields showed a clear bitemporal deficit that was more dense in the superior regions. This prompted the need for threshold automated perimetry to provide more precise quantification. Clinicians experienced in diagnosing neurological disease often prefer a visual field test that measures the threshold for points within the entire central 30 degrees. Automated tests are consistent, repeatable and often come with software that allows you to monitor changes.16 Unfortunately, these tests are often long and taxing, especially for individuals with deficits.16 If systemic neurological or other neuro-ophthalmic symptoms are present, without definitive central defects, a peripheral 30-60-degree threshold may uncover visual field compromise in the periphery.16 When patients can't sit or concentrate for long periods, cannot return to the office or require a more expeditious evaluation, shorter tests are acceptable. When you suspect a lesion, refer the patient to a neurologist or neuro-ophthalmologist for further testing. In appropriate cases thin-section computed axial tomography, MRI with gadolinium and radioimmunoassay for detecting prolactin hormone, along with other laboratory tests are indicated. If the adenoma remains small enough not to cause symptoms, the neurologist might simply choose to monitor the patient's condition. Other management options include: • Transsphenoid resection. The current research and literature show that the neuro-ophthalmological community supports transsphenoidal resection as the pre- ferred procedure for removing pitutitary tumors. Surgery is indicated if there is evidence of tumor enlargement, especially when accompanied by compression of the optic chiasm, invasion of the cavernous sinus or the development of pituitary hormone deficiencies.13 Visual improvement following treatment is often dramatic, with the greatest degree occurring within the first few months.13 Complications of transsphenoidal resection include cerebrospinal fluid rhinorrhea (discharge from nasal mucous membranes), diabetes insipidus and sinusitis.12,13 • Medication. This treatment is limited to prolactinomas. Bromocriptine, a dopamine agonist, is useful in shrinking these tumors. Bromocriptine works by inhibiting pituitary gonadotrophic function, reducing prolactin secretions, and helps to diminish the size of these tumors. These patients maintain low-dose therapy of bromocriptine for life. If they discontinue drug therapy, the adenoma often regrows and enlarges.12,13 • Radiotherapy . Conventional radiotherapy is usually adjunctive to prevent tumor regrowth.12,13 Whatever treatment the neurologist or neuro-ophthalmologist chooses, patients must undergo neurological and automated perimetry tests in a serial fashion, at regular intervals, so you can monitor their progress. This case presents several important lessons. Although confrontation fields first revealed a bitemporal defect in this patient, an automated visual field exam is still necessary for more accurate findings. It was also important to recognize that these visual field defects pointed to a systemic problem. Timely referral to a specialist ultimately helped save this patient's vision. Overall, this patient demonstrates how optometrists can play a vital role in pinpointing systemic disease and comanaging the patient with other professionals.
Dr. Gurwood is an associate professor of clinical sciences and senior attending optometric physician at The Eye Institute of the Pennsylvania College of Optometry. Dr. Ari is an optometrist in the United
States Armed Forces. Dr. Golde is in private practice. 1. Wormington CM. Pituitary adenoma: diagnosis and management. J Am Optom Assoc 1989;60(12):929-35. |
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