Figure 1: The right (a) and left (b) optic nerve heads and vessels are obscured by a fluffy white mass.
An otherwise healthy 14-year-old male was referred to the Neuro-ophthalmology service for abnormal optic nerves. He had recently had a seizure after falling from a tree. His head CT was normal, but an undilated eye exam in the emergency room was concerning for papilledema. At the time of evaluation, he denied decreased visual acuity, decreased visual fields, diplopia, or transient visual changes. A full neuro-ophthalmologic exam was done and revealed normal visual acuity, color vision, and visual fields to confrontation. His pupils were symmetric without evidence of a relative afferent defect. Anterior segment exam was normal, and the dilated fundus exam demonstrated the findings seen in Figure 1a and 1b.
What is the presumed diagnosis? What is the management plan?
Answers to the Neuro-Ophthalmology Case Quiz
The examination is significant for elevated irregular fluffy white material over and surrounding both optic nerve heads. The 2 most common etiologies on the differential diagnosis are myelinated retinal nerve fibers (MRNF) or bilateral infiltrative optic neuropathy. The normal afferent examination along with the lack of retinal hemorrhages or other signs of ocular inflammation favors a diagnosis of MRNF.
MRNF is typically a benign congenital finding that is static and asymptomatic, although rare acquired cases have been reported. Typically, myelination of visual pathway axons progress toward the eye but stop before entering the eye and effecting the retina. It is believed that oligodendrocytes that produce myelin fail to stop at the end of the optic nerve, and myelinate the retinal nerve fibers.
Evaluating a patient with an abnormal optic nerve should always include a thorough history to identify symptoms of elevated intracranial pressure. When an infiltrative optic neuropathy secondary to leukemia or lymphoma is suspected, additional questions about fatigue, weight loss, and chronic fever should be asked. Patients with MRNF can demonstrate mild visual field defects. Beyond the comprehensive examination, additional diagnostic studies can include visual field testing, retinal imaging, blood tests, and brain imaging.