Pediatric patient presents with acute onset of vision loss

At presentation, the boy also had an afferent pupillary defect.

Issue: August 25, 2015

ByKristen E. Dunbar, MD

BySylvia H. Yoo, MD

An 8-year-old Asian boy presented with vision loss in the right eye for 1 day. He described a central area of vision loss with intact peripheral vision. At the onset of the vision loss, he had a mild headache that resolved. He did not have any eye pain or diplopia, and there were no changes in the left eye. He had no other neurologic changes and no recent illnesses or vaccinations. He was otherwise healthy.

Examination

Visual acuity with myopic correction was count fingers at face in the right eye and 20/20 in the left eye. There was an abnormal optokinetic nystagmus (OKN) response in the right eye. The patient’s pupils had been dilated by the referring physician but reportedly had a 2+ afferent pupillary defect, which was confirmed the day after presentation. Extraocular motility was full without pain or nystagmus. Ishihara color plate testing was decreased in the right eye to 0/10 and normal in the left eye. Anterior and posterior segment examinations were unremarkable with the exception of mild nasal elevation of the right optic nerve head.

What is your diagnosis?

Acute onset of decreased vision

Acute onset of decreased vision in a child with a normal exam may lead to a diagnosis of functional vision loss after careful exam and follow-up. In this patient with acute unilateral vision loss, however, an abnormal OKN response and relative afferent pupillary defect were also present. Given these findings, the possibility of a retrobulbar lesion causing an optic neuropathy was considered.

The differential diagnosis for optic neuropathy can be divided into several categories: ischemic, compressive, infiltrative, traumatic, mitochondrial and inflammatory (optic neuritis). Despite the lack of other neurological changes, given the acute onset and severity of vision loss, the patient’s presentation was concerning for optic neuritis associated with neuromyelitis optica (NMO) or multiple sclerosis. Leber’s hereditary optic neuropathy, post-infectious optic neuritis and a retrobulbar compressive lesion were also in the differential.

Management

The patient was admitted to the hospital for further work-up and started on intravenous methylprednisolone. The following labs were sent: CBC, ESR, Lyme titers, ACE, VDRL, FTA-ABS, QuantiFERON Gold and NMO antibody. A lumbar puncture was performed and cerebrospinal fluid sent for cell count, protein and oligoclonal bands. All labs were negative. An MRI of the orbit, brain and spine with gadolinium and fat suppression revealed intracanalicular right optic nerve enhancement and a few scattered nonspecific foci of T2/FLAIR hyperintense signals involving the subcortical white matter of the bilateral frontal lobes (Figure 1). A diagnosis of right retrobulbar optic neuritis was made.

Figure 1. MRI of the orbit coronal section shows enhancement of the right intracanalicular portion of the right optic nerve.

Discussion

Optic neuritis is an inflammation of the optic nerve associated with decreased vision and optic nerve dysfunction causing visual field defects, dyschromatopsia, decreased contrast and afferent pupillary defect. It may be associated with periorbital pain. The incidence in the adult population is estimated to be one to five per 100,000 per year.

Optic neuritis in the pediatric population is less common and considered to be a different disease process than in adults. Pediatric optic neuritis is typically bilateral, associated with infectious etiologies and often has a better visual prognosis than adult counterparts. Several infectious diseases have been associated with optic neuritis, including measles, mumps, varicella, rubella, brucella, pertussis, mononucleosis, Bartonella, toxoplasmosis, Q fever, Ebola, mycoplasma, enterovirus, herpes simplex and Lyme disease. Immunizations for diphtheria, pertussis and tetanus have also been associated with optic neuritis.

Most concerning is the association among optic neuritis, MS and NMO. However, unlike in adults, in which the probability of association with MS can reach 38% in the 10 years after an attack (higher if abnormalities on brain MRI), in children, the largest research sample by Luchinetti and colleagues reported a 13% risk in the 10 years after an attack and only 26% by 40 years. They also showed a lower risk for recurrent optic neuritis in children compared with adults.

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While adult optic neuritis has been studied extensively in large prospective trials, the rarity of pediatric neuritis has limited published reports to retrospective studies and case series. Waldman and colleagues performed a systematic literature review and meta-analysis of observational studies of pediatric optic neuritis. They found that unilateral optic neuritis occurred more frequently in older children and that there was no correlation between development of optic atrophy and initial visual acuity. Older children and children with brain MRI abnormalities at presentation were at greater risk for developing MS. It is unclear whether unilateral or bilateral optic nerve disease portends a higher risk for developing MS. There may also be an association between ethnicity and development of MS after an episode of optic neuritis.

Due to the lack of large prospective studies of pediatric optic neuritis, the treatment of optic neuritis in children is typically based on the results of the Optic Neuritis Treatment Trial (ONTT). The ONTT found that treatment of optic neuritis with intravenous corticosteroids increased the rapidity of visual improvement but did not improve the final visual acuity outcome. Treatment with oral corticosteroids alone was found to increase the rate of recurrent optic neuritis. Prospective outcomes studies are needed to further study the natural history of pediatric optic neuritis and determine evidence-based treatments in the pediatric population.

Follow-up

The patient was discharged after 5 days with an oral steroid taper. Visual acuity gradually improved to 20/20 over the next month despite persistence of the afferent pupillary defect.

References:
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For more information:
Kristen E. Dunbar, MD, and Sylvia Yoo, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.
Edited by Kristen E. Dunbar, MD, and Kendra Klein, MD. They can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St, Box 450, Boston, MA 02111; website: www.neec.com.