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Backgrounds: The distinction between neuromyelitis optica (NMO) and multiple sclerosis (MS) has long been a debate in Asia. The most specific finding for NMO is a longitudinally extensive, central cord lesion on MRI in the setting of myelitis (LETM), which is very rare in MS. The MRI criterion for LETM (contiguous spinal cord lesion 3 or more segments in length) is crucial. However its sensitivity and specificity are not well known. Objective: We aimed to assess the usefulness of the supportive diagnostic criterion for NMO myelitis in a cohort of patient who had myelitis from MS or NMO and NMO spectrum disorder (NMOSD). Methods: From the Korean MS registry between 2007 and 2009, 300 patients presented with myelitis from MS or NMO and NMOSD. Among those, our study included 151 patients whose brain and spinal cord MRIs were available. We applied their MRI findings to a LETM criterion and analyzed their demographic, imaging features. Results: Among 151 included patients, 50 patients had MS (19 males and 31 females, mean age of onset 32.5 years and disease duration 5.2 years) and 101 had NMO and NMOSD (13 males and 88 females, mean age of onset 34.6 years and disease duration 6.0 years) with? anti-aquaporin-4 antibody (77/101, 76%). There was no differences in age, onset age and disease duration between two groups, however, a significant female predominance (88%) in NMO and NMOSD. Twelve patients of NMO and NMOSD (13%) had cord lesion less than 3 vertebral segments and 7 of MS (14%) had LETM. The sensitivity of LETM criterion was 88%, the specificity was 86% and the accuracy was 87%. There were significant differences in cord MRI findings between two groups, in terms of multiple lesions (MS 28/50, NMO 29/101), cord swelling (MS 13/50, NMO 68/101), central cord lesion (MS 19/50, NMO 86/101) and cord atrophy with follow-up MRI (MS 1/50, NMO 34/101). Overall demographic, clinical and imaging features of 151 patients diagnosed as MS or NMO and NMOSD were not different from those previously reported. Conclusions: Our results suggest two things, (1) the LETM MRI criterion is very useful in differentiation between NMO and MS; (2) even though a LETM is characteristic of NMO, some patients have overlapping MRI features at least in Korean population.

Read More: Is the cord lesions extending over three or more vertebral segments sufficiently specific to distinguish neuromyelitis optica from multiple sclerosis?