Clinical features and visual outcome of pediatric optic neuritis

Pediatric optic neuritis (PON), an inflammatory disorder of the optic nerve, is rare, not well-studied, and has limited data. It accounts for 25% of acute pediatric demyelinating syndromes. Although children have poor visual acuity at presentation, the recovery in children is remarkable with a return close to baseline functioning. Almost 89% recover vision >20/40.[1] The PON prospective outcome study[2] was the first prospective study in the western literature to analyze the visual outcome of PON and noted a marked improvement in visual acuity at 6 months and maintenance of good vision at 2 years despite poor vision in 81% at presentation. The current study[3] serves as the only prospective Indian study of PON. It also noted good visual outcome at 3 months despite poor visual acuity in 81% at presentation. PON differs from adult optic neuritis in its clinical manifestation. The most significant difference is the frequency of bilateral presentation (simultaneous or sequential), especially under 10 years, of age as compared to adults. Interestingly, both the PON prospective outcome study[2] and the current study[3] noted that unilateral disease was more common in their series. In prepubertal children, boys and girls can be equally affected. The Indian study noted female preponderance (ages ranging from 5 to 14 years) unlike the PON prospective study (ages ranging from 5 to 15 years). Another feature of notable difference is the presence of papillitis (60–70%) as opposed to around only 30% in adults.[4,5] Disc edema was noted in almost 78% of children in the present study. Pain in eye movements while classical and universal in adults was only reported in 50% of cases[1] and only noted in 26% in the present study.[3] Relative afferent pupillary defect (RAPD) has been reported in 67% of cases in one study.[6] The Indian study noted RAPD in almost 96%. Like other studies,[6] color vision deficits were noted in 26% at presentation and not elicitable in 74% due to poor vision at presentation. Visual field and optical coherence tomography (OCT) should be included where possible. Centrocaecal scotoma was noted in 7.4% of cases, with generalized constriction in 11.1%. Retinal nerve fiber layer on OCT, as in adults, shows thinning in previously affected eyes and a gradual decrement with subsequent attacks that could correspond to the lag in recovery of visual function in terms of contrast, color vision, and fields. All cases of PON should undergo magnetic resonance imaging (MRI) head and orbits with contrast and a spinal tap. The imaging characteristics for PON on MRI tend to remain similar to adults, with more extensive optic nerve involvement suggestive of neuromyelitis optica – myelin oligodendrocyte glycoprotein (NMO-MOG) disorder. Perivenous distribution of demyelinating lesions suggests acute disseminated encephalomyelitis (ADEM). PON can be monophasic. But if during workup the MRI shows white matter lesions and there are oligoclonal bands in cerebrospinal fluid (CSF), this could help establish risk for multiple sclerosis (MS) in future[7] and understand the course, prognosis, and treatment options. There is a lack of evidence on treatment for PON; a treatment used in adult population is extrapolated for this age group. Initial treatment is with high-dose IV steroids; if visual recovery is poor or with recurrence, one could consider intravenous immunoglobulin and plasma exchange though the evidence is limited to case reports and series. PON may follow a febrile illness. It could herald the initial demyelinating event for ADEM, MS, neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein (MOG)-associated disease (MOGAD).[8] In the prospective PON study,[2] 61% were noted to have associated neurologic autoimmune disease: ADEM in 7%, MS in 14%, NMOSD in 11%, and MOGAD in 29%. In the prospective Indian study,[3] 19% had MS, which was slightly higher compared to other retrospective Indian PON studies.[9-11] The PON prospective study[2] showed that isolated optic neuritis at onset reduces the chances of recurrence and development of associated neurologic disease. Though bilateral optic nerve involvement could be a monophasic event with a subsequent good outcome, NMOSD needs to be considered, especially when recovery with steroids is poor. This requires testing for aquaporin/MOG antibodies as well as other markers like anti Sjogren’s syndrome related antigen A (SSA), antinuclear antibody (ANA). ADEM typically though is a monophasic event. Optic neuritis secondary to ADEM has recently been found to be associated with MOG Ab in almost 40–50%. Longitudinal follow-up of MOG Ab titers in these patients showed persistently high titers in those with multiple attacks and incomplete recovery[12] and an indication for favorable outcome in those with a serial reduction in their titers. This could potentially serve as a marker for those who may require prolonged treatment beyond.[13] Factors that increase the risk for MS include Human Leucocyte antigen- DRB1 HLA-DRB1*15 alleles, remote Epstein-Barr virus infection, and low serum 25-hydroxyvitamin D concentrations.[14] The lack of oligoclonal bands on CSF and the absence of characteristic MS-like lesions also help in distinguishing MS from other demyelinating diseases and deciding on appropriate treatment.