Longitudinally extensive transverse myelitis (LETM) is caused by a myriad of etiologies. We present a case of Neuromyelitis Optica Spectrum Disorder (NMOSD)-related myelitis, initially seronegative, masquerading as VZV-related myelitis.

A woman in her sixties reported a one-month history of bilateral lower extremity paresthesias and weakness. Days prior, she felt tingling on her back with eruption of a painful rash, and was diagnosed with varicella zoster (VZV). She had transient improvement, before worsening 2 months later with involvement of the arms and signs of myelopathy on exam. MR imaging revealed a long segment T2 hyperintense cord expansion extending from the medulla throughout the thoracic spine with additional hyperintensities in the conus medullaris with patchy enhancement. Work up was significant for lymphocytic-predominant CSF pleocytosis with elevated protein and IgG index. Serum VZV IgG was positive with negative IgM. CSF VZV PCR was negative. Aquaporin-4 antibody was negative. Testing for other causes of myelopathy was unrevealing. She was treated with IV Acyclovir, IV pulse steroids, and subsequently plasma exchange. She improved without further immunomodulation. Three months later, she had another attack and imaging showed new occipital enhancing lesion consistent with demyelination. At this visit, aquaporin-4 antibodies returned positive with a titer of 1:100. She received IV steroids and started rituximab.