Bright spotty lesions on the spinal cord: an additional MRI indicator of neuromyelitis optica spectrum disorder?

Neuromyelitis optica spectrum disorder (NMOSD) is a devastating inflammatory disease of the central nervous system (CNS), thus, an early and accurate diagnosis is important.1 The aquaporin-4 (AQP4) antibody is a specific marker of NMOSD that has generally modest sensitivity but is not always available in time. The radiological characteristics, such as longitudinally extensive transverse myelitis (LETM), are helpful in the diagnosis, but LETM is not a pathognomonic feature of NMOSD. Therefore, it would be good to identify the other specific features associated with NMOSD. Bright spotty lesions (BSLs) on spinal MRIs have recently been identified as a discriminative feature that distinguishes NMOSD from multiple sclerosis (MS).2 However, previous study was conducted with a small number of patients and the timing of the MRIs was not controlled. Furthermore, it has not been investigated whether BSLs may help to discriminate NMOSD from other entities, such as idiopathic transverse myelitis (ITM), which share many similar features with NMOSD. Thus, the present study investigated whether BSLs can be utilised as a discriminative feature of NMOSD to distinguish it from MS and ITM in a large cohort of patients with myelitis, particularly during the acute phases. A total of 114 patients, who presented with acute myelitis and underwent spinal MRIs (≤3 weeks since the latest clinical attack), were enrolled from the National Cancer Centre registry of CNS idiopathic inflammatory diseases between 2005 and 2014. Of 114 patients, 59 patients with NMOSD were positive for AQP4 antibody, 31 patients met the McDonald criteria for MS and 24 patients fulfilled the criteria for ITM.3 All patients with MS and ITM were negative for AQP4 antibody following repeated assays of three different methods.4 Myelin-oligodendroglycoprotein (MOG) antibodies were also tested using a cell-based assay at Tohoku University and all patients were negative for MOG antibodies.4 …