Late Onset Chiasmal Neuritis in Newly Diagnosed Neuro-myelitis Optica

A 70-year-old African American woman presented with loss of vision in both eyes. She noted cloudiness in both eyes with mild headache and possible flu-like symptoms of body fatigue. The past medical history was of hypothyroidism on levothyroxine. Initial visual acuities were 20/250 in both eyes with bitemporal field loss to confrontation count fingers testing. Ishihara color plates were reduced in both eyes missing the temporal numbers in most plates. Intraocular pressured were 9 OD and 8 mm of Hg OS. Slit lamp exam showed cataractous changes in both eyes. The fundus exam was normal upon presentation. Humphrey visual fields showed dense central and temporal visual field defects in both eyes. Combined optical coherence tomography of the retinal nerve fiber layer (RNFL) and ganglion cell GCL) were normal in both eyes. Magnetic resonance imaging(MRI) of the brain and orbits without gadolinium (patient request) revealed a thickened chiasm and high signal in both optic tracts. The patient was admitted for work up and received 7 total days of 1gram intravenous Solumedrol and lab work. The vision recovered to 20/30 and 20/20 over two month's period. Lab work revealed a positive Aquaporin 4 IgG cell-based assay as seen in neuro myelitis optica (NMO). Repeat MRI of the brain and orbits with gadolinium revealed resolution of the chiasmal neuritis and the optic tract signal. The patient was referred to neuro-immunology for further management for NMO. Neuromyelitis optica (NMO) is an autoimmune demyelinating disorder of the central nervous system that tends to affect the optic nerves and the spinal cord. Diagnostic criteria have been updated as of 2015 and include criteria such as having positive test for aquaporin 4, having optic neuritis, transverse myelitis or area postrema syndrome and excluding other cause such as multiple sclerosis. Acute treatments involve the use of steroids including intravenous Solumedrol, plasmapheresis and intravenous immunoglobulin. Maintenance treatments include the use of azathioprine, mycophenolate, rituximab and other newer medications. Chiasmal neuritis is fairly rare and when encountered presents with bilateral visual loss with variable degrees of bitemporal visual field deficits. Chiasmal neuritis can be seen in inflammatory conditions such as multiple sclerosis, NMO as well as sarcoid and myelin oligo dendroglycoprotein associated diseased (MOG-AD) among other rarer non-inflammatory causes such as Leber Hereditary Optic Neuropathy and toxic optic neuropathies. Age of onset of NMO on average is 38 years but can range from age 2 to 86. Late onset NMO is considered to start at age 50 or older and have been reported to have greater severity including higher motor weakness and death. In summary, late onset NMO and chiasmal neuritis are both rare presentations of NMO. We must still consider the diagnosis of NMO in patients older than 50 and in any case that has chiasmal neuritis.