Brighter spotty lesion on spinal MRI: Is it helpful in differentiating AQP4 antibody positive neuromyelitis optica spectrum disorder from MOG antibody associated disease?

Abstract

Introduction: Brighter spotty lesion (BSL) in the spinal cord was reported to be seen exclusively in aquaporin-4-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD), but not in multiple sclerosis or seronegative myelitis. Myelitis in AQP4-NMOSD and myelin oligodendrocyte glycoprotein antibody disease (MOGAD) shares common clinical and radiological features, such as longitudinally extensive transverse myelitis (LETM), despite the differences in their pathogenesis.

Objectives & Aims: We aimed to determine whether BSL on spinal magnetic resonance imaging (MRI) can help distinguish AQP4-NMOSD from MOGAD.

Methods: Fifty participants with MOGAD from six Korean medical centres and 61 age-/attack severity matched participants with AQP4-NMOSD from the National Cancer Center, Korea, were enrolled. A total of 134 spinal MRI scans (66 scans from MOGAD and 68 from AQP4-NMOSD) acquired within 1 month from attack were analysed independently by a neuroradiologist and two neurologists blinded to the diagnosis. The presence of BSL and the lesion length were evaluated. BSL was defined as a more hyperintense spotty lesion on axial T2-weighted imaging (WI) than usual T2-hyperintense lesion, with signals at least as high as the surrounding cerebrospinal fluid on T2WI but not as low as that on T1WI.

Results: BSLs were observed in 18 of 61 (30%) participants with AQP4-NMOSD, whereas only 1 of 50 (2%) participants with MOGAD showed BSL (p < 0.001). LETM (lesion length over three vertebral segments) was common in both AQP4-NMOSD (54/61, 89%) and MOGAD (32/50, 64%) but with a significant difference (p = 0.0028). Two AQP4-NMOSD participants without LETM showed BSLs.

Conclusion: These results suggest that BSL seen in the acute phase is a useful MRI feature to differentiate AQP4-NMOSD from MOGAD.