NMO-IgG DETECTED IN CSF IN SERONEGATIVE NEUROMYELITIS OPTICA

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Abstract
Neuromyelitis optica (NMO) is an inflammatory and demyelinating disease characterized by recurrent attacks of optic neuritis (ON) and longitudinally extensive transverse myelitis (LETM).1 NMO is associated with antibodies against the aquaporin-4 (AQP4) water channel.2 NMO–immunoglobulin G (IgG) predicts a relapsing course and is a supportive criterion for NMO.3–5 The high risk of relapse, sometimes with devastating effects, makes early diagnosis important. Early identification permits counseling and consideration for immunosuppressive therapy. The serum NMO-IgG assay, using indirect immunofluorescence, is 73% sensitive and 91% specific for clinically defined NMO.6 While helpful when positive, the sensitivity is insufficient to exclude the diagnosis. We describe 3 of 26 patients with NMO at our institution with NMO-IgG positivity restricted to CSF. ### Case reports. #### Case 1. A 25-year-old African American woman presented with leg numbness and mild tetraparesis that resolved over 1 month. Two months later, she developed a midthoracic sensory level, again with recovery. The next month, bilateral leg weakness impaired her ability to ambulate. MRI (figure, A–C) demonstrated T2 hyperintensities (T2H) and patchy enhancement spanning the medulla through C7 and T2–T11. Brain MRI revealed a single nonspecific T2H. Visual evoked potentials (VEPs) were normal. Serum NMO-IgG was negative but CSF NMO-IgG was positive. IgG index was elevated to 0.79, CSF leukocytes were 24/μL, but albumin index, IgG synthesis, and oligoclonal bands (OCBs) were normal. Serum antinuclear antibodies (ANA) were negative. Treatment included IV glucocorticoids and rituximab with no further exacerbations. After 8 months of disease, Expanded Disability Status Scale (EDSS) was 6.0. Figure Neuroimaging of CSF antibody-positive neuromyelitis optica Case 1: Sagittal T2-weighted STIR …