Neuromyelitis optica spectrum disorders with an inverted V sign on spinal cord magnetic resonance imaging: antiaquaporin-4 antibody and functional vitamin B12 deficiency

Several studies have reported a possible link between antiaquaporin- 4 antibody and vitamin B12 deficiency in neuromyelitis optica spectrum disorder (NMOSD). Bilaterally symmetric hyperintense signals on magnetic resonance imaging (MRI) of the posterior columns, called the inverted V sign, are a characteristic feature of subacute combined degeneration associated with vitamin B12 deficiency. We report a patient with anti-aquaporin-4 antibodypositive NMOSD and an inverted V sign on MRI of the spinal cord and address the association between anti-aquaporin-4 antibody and functional vitamin B12 deficiency.