Bright spotty lesions as an imaging marker for neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is a rare inflammatory demyelinating disorder of the central nervous system (CNS). Aquaporin-4 (AQP4) antibodies in the serum are highly specific for the diagnosis of NMOSD, but the sensitivity remains under 90% allowing for diagnosis of AQP4 IgG seronegative disease. It remains of crucial importance to identify seronegative NMOSD myelitis as early as the first attack to initiate long-term treatment that will reduce future relapses and disability and to avoid potentially harmful treatments such as those of multiple sclerosis (MS). Over the years, many spinal imaging features have been reported to favour the diagnosis of NMOSD, but only longitudinally extensive transverse myelitis (LETM) was specific enough to make the diagnostic criteria in the AQP4 IgG seronegative cases. Bright spotty lesions (BSLs), which are defined as hyperintense lesions on axial T2-weighted images and sometimes associated with T1 low signal, are now reported to have a higher specificity and sensitivity compared to LETM in predicting a diagnosis of NMOSD against other causes of myelitis. In the review, we aim to highlight the position of BSLs in diagnosing NMOSD as well as its possible role as a prognostic factor for the clinical outcome.