Woman presents with bilateral optic nerve edema

The patient did not report any diplopia or transient visual obscurations.

Issue: December 10, 2018

ByMalgorzata Dymerska Peterson, MD

ByLaurel N. Vuong, MD

A 30-year-old woman was referred to the New England Eye Center neuro-ophthalmology service for evaluation of bilateral optic disc swelling found incidentally during her annual eye examination.

Her ocular history was notable only for a refractive error, for which she wore contact lenses. Her medical history included a long-standing seizure disorder, for which she had had multiple normal MRIs, obesity (BMI of 42), polycystic ovary syndrome, temporomandibular joint dysfunction (TMJ) and generalized anxiety disorder. Review of systems revealed frequent stable headaches thought to be secondary to TMJ. Additionally, she endorsed recent onset of intermittent intracranial noises and a 20-pound weight gain over the past year. She did not have any diplopia or transient visual obscurations. She did not take any vitamin A-derived medications, minocycline/tetracycline, oral contraceptives or steroids. However, she had a levonorgestrel intrauterine device (IUD). The rest of her review of systems was unremarkable.

Examination

**Figure 1.** Disc photos show bilateral disc edema more prominent in the right eye.

**Figure 2.** Visual field testing shows a slightly enlarged blind spot in the right eye and normal visual field in the left eye.

**Figure 3.** OCT shows swelling of both optic nerves with retinal nerve fiber layer thickness greater in the right eye than the left.

On examination, visual acuity with correction was 20/20 bilaterally. Pupils were equally reactive to light with no relative afferent pupillary defect. IOP was 19 mm Hg in the right eye and 18 mm Hg in the left eye. Confrontation visual fields were full in both eyes, and color vision was normal. Ocular motility was full. Anterior segment exam was unremarkable. Funduscopic examination was notable for mild optic disc edema bilaterally (Figure 1).

Humphrey visual fields 30-2 showed a slightly enlarged blind spot in the right eye and a normal visual field in the left eye (Figure 2). OCT of the optic nerves showed an average retinal nerve fiber layer thickness of 128 µm in the right eye and 113 µm in the left eye (Figure 3).

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Optic disc edema

Given our patient’s gender, age, body habitus and recent weight gain, idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, was at the top of the differential. However, other causes of elevated intracranial pressure (ICP) need to be considered before a diagnosis of IIH is made. This includes masses obstructing cerebrospinal fluid outflow, venous sinus thrombosis and venous sinus stenosis. If she had other associated symptoms, meningitis could also be considered. In addition to elevated ICP, inflammatory and infectious optic neuritis may also present as bilateral disc swelling, although she did not have any pain with eye movement or blurred vision, which typically accompanies optic neuritis. The appearance of her optic nerve swelling was not consistent with an infiltrative optic neuropathy. Finally, structural optic nerve abnormalities such as disc drusen may sometimes be misdiagnosed as disc edema.

Additional workup

MRI of the orbits with contrast did not show any masses or optic nerve enhancement. MRI of the brain showed a multicystic nonenhancing lesion centered in the midbrain involving both the tectum and tegmentum. The lesion had a mass effect on the cerebral aqueduct, causing obstructive hydrocephalus (Figure 4). MRV of the brain did not show any evidence of venous sinus thrombosis or stenosis. Lumbar puncture was deferred at this point, given the finding of hydrocephalus on imaging.

**Figure 4.** MRI of the brain shows a multicystic lesion (white arrow) in the midbrain with secondary obstructive hydrocephalus (blue arrow).

Discussion

Papilledema is commonly understood to refer to optic nerve edema due to increased ICP. Both optic nerves are usually involved, although the edema can be asymmetric. There are a number of possible etiologies for elevated ICP, including obstructive masses, meningitis, cerebral hemorrhage, venous sinus thrombosis and venous sinus stenosis. Certain medications have been associated with elevated ICP. This includes steroids, vitamin A analogs and tetracyclines. The etiology of increased risk of elevated ICP with use of these medications is not known. However, it has been postulated that vitamin A derivatives, for example, may reduce cerebrospinal fluid (CSF) absorption by decreasing the absorptive function of arachnoid villi. There have also been some reports of increased risk of increased ICP with the use of oral contraceptives, as well as with levonorgestrel IUD, which our patient had, but the mechanism is not understood.

Despite a clinical presentation highly suggestive of IIH, our patient was found to have an obstructive mass, which highlights the importance of neuroimaging in these cases. Mass lesions in the brain cause elevated ICP by increasing CSF volume secondary to obstruction of the ventricles. Patients presenting with papilledema and/or symptoms consistent with increased ICP (headache, pulsatile intracranial noises, diplopia, transient vision loss) must undergo neuroimaging. Reports in the neurosurgical literature found that up to 80% of patients with brain tumors had papilledema. Generally, masses that are infratentorial are more likely to obstruct CSF outflow through the cerebral aqueduct than supratentorial lesions; therefore, infratentorial masses are more likely to be associated with papilledema. Treatment of papilledema secondary to mass lesions generally involves surgical excision of the mass, if the risk is low. When the location of the mass precludes excision, the CSF flow can be diverted using shunts or ventriculostomies.

The diagnosis of IIH is a diagnosis of exclusion. IIH typically occurs in women who are young and obese with recent weight gain. In the United States, the incidence of IIH has been estimated at 0.9 per 100,000 of all people and at 3.5 in women between the ages of 15 and 44 years. The modified Dandy criteria help guide the diagnosis of IIH. With symptoms typical of increased ICP, or papilledema, patients need to undergo imaging and lumbar puncture. In IIH, the opening pressure is elevated and the CSF composition is normal. Treatment depends on the severity of vision loss. Unlike obstructive causes of elevated ICP, in IIH cases in which there is minimal to no vision loss, management can be conservative. Patients are asked to lose about 7% to 10% of their total weight, and this alone can be curative. When there is some degree of vision loss, administration of carbonic anhydrase inhibitors, specifically acetazolamide, is often prescribed while the patient works on weight loss. Topiramate and furosemide, which are not first-line treatments, have been used in some cases if the patient cannot tolerate acetazolamide. If the vision loss worsens on medical management or if the vision loss is severe on initial presentation, surgical interventions such as CSF shunting, venous sinus stenting or optic nerve sheath fenestration should be considered.

**Figure 5.** Disc photos 5 months after endoscopic third ventriculostomy demonstrate resolution of disc edema.

Clinical course continued

Our patient was referred for neurosurgical evaluation. Given the location and appearance most consistent with a low-grade glioma, neurosurgery recommended close observation of the lesion for growth. For treatment of the obstructive hydrocephalus, the patient underwent endoscopic third ventriculostomy, which involves endoscopic creation of a drainage path in the floor of the third ventricle to relieve the accumulation of CSF. Cytology performed on a sample of CSF revealed no malignant cells. A follow-up exam 5 months after the surgery revealed resolution of the papilledema (Figure 5).