Neuromyelitis optica spectrum disorder in a patient with neurofibromatosis type 1 mimicking spinal cord infarction.

A man in his 70s with neurofibromatosis type 1 (NF1) developed tetraplegia and bowel and bladder dysfunction over 5 days. MR scan of the spine showed a longitudinally extensive lesion in the anterior spinal cord, with diffusion restriction characterised by hyperintensity on diffusion-weighted imaging and corresponding hypointensity on the apparent diffusion coefficient map, localised to the anterior spinal artery territory. These findings initially led to a diagnosis of spinal cord infarction attributed to NF1 vasculopathy. However, on day 29, we identified aquaporin-4 antibody on cell-based assay, prompting a revised diagnosis of neuromyelitis optica spectrum disorder (NMOSD) despite initially negative ELISA results. While NF1 is associated with cerebrovascular diseases and some neurological disorders, such as multiple sclerosis, NMOSD is rare. This case underscores the diagnostic challenge of differentiating NMOSD from vascular myelopathy in patients with pre-existing vascular risk factors.