Objective We assessed the frequency and characteristics of ring-enhancing spinal cord lesions in neuromyelitis optica spectrum disorder (NMOSD) myelitis and myelitis of other cause.
Methods We reviewed spinal cord MRIs for ring-enhancing lesions from 284 aquaporin-4 (AQP4)-IgG seropositive patients at Mayo Clinic from 1996 to 2014. Inclusion criteria were as follows: (1) AQP4-IgG seropositivity, (2) myelitis attack and (3) MRI spinal cord demonstrating ring-enhancement. We identified two groups of control patients with: (1) longitudinally extensive myelopathy of other cause (n=66) and (2) myelitis in the context of a concurrent or subsequent diagnosis of multiple sclerosis (MS) from a population-based cohort (n=30).
Results Ring-enhancement was detected in 50 of 156 (32%) myelitis episodes in 41 patients (83% single; 17% multiple attacks). Ring-enhancement was noted on sagittal and axial images in 36 of 43 (84%) ring enhancing myelitis episodes and extended a median of two vertebral segments (range, 1–12); in 21 of 48 (44%) ring enhancing myelitis episodes, the ring extended greater than or equal to three vertebrae. Ring-enhancement was accompanied by longitudinally extensive (greater than or equal to three vertebral segments) T2-hyperintensity in 44 of 50 (88%) ring enhancing myelitis episodes. One case of a spinal cord biopsy during ring-enhancing myelitis revealed tissue vacuolation and loss of AQP4 immunoreactivity with preserved axons. The clinical characteristics of ring-enhancing myelitis episodes did not differ from non-ring-enhancing episodes. Ring-enhancing spinal cord lesions were more common in NMOSD than other causes of longitudinally extensive myelopathy (50/156 (32%) vs 0/66 (0%); p≤0.001) but did not differ between NMOSD and MS (50/156 (32%) vs 6/30 (20%); p=0.20).
Conclusions Spinal cord ring-enhancement accompanies one-third of NMOSD myelitis episodes and distinguishes NMOSD from other causes of longitudinally extensive myelopathies but not from MS.
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Contributors NLZ is the lead author and was involved in data acquisition. PPM contributed to radiographic data review. BGW was involved in critical revision of manuscript. CFL conducted pathology review and critically revised the manuscript. YG was involved in pathology review. SJP critically revised the manuscript. KNK reviewed radiographic data. TJK, DMW and NK critically revised the manuscript. EPF contributed to study and concept design, analysis and interpretation, and critically revised the manuscript.
Competing interests NLZ, PPM, NK, EPF, YG and KNK have no disclosures. BGW receives royalties from RSR and Oxford University for technology licence for AQP4 autoantibodies used for diagnosis of neuromyelitis optica. He serves on data safety monitoring committees for Novartis, Biogen-Idec and Mitsubishi pharmaceutical companies, and serves on an adjudication panel for MedImmune Pharmaceuticals. He served as a consultant for GlaxoSmithKline, Elan, Ono, Chugai and Alexion and Novartis pharmaceutical companies. He serves on editorial boards for Neurology, the Canadian Journal of Neurological Sciences and Turkish Journal of Neurology. CFL shares in royalties from marketing of kits for detecting AQP4 autoantibody and from the sale of Blue Books of Neurology: Multiple Sclerosis 3 (Saunders Elsevier, 2010); she receives research support from Biogen, Novartis, Alexion, and Sanofi. SJP is a named inventor on patents (#12/678,350 filed 2010 and #12/573,942 filed 2008) that relate to functional AQP4/NMO-IgG assays and NMO-IgG as a cancer marker; receives research support from Alexion Pharmaceuticals, the Guthy-Jackson Charitable Foundation and the National Institutes of Health (NS065829). SJP has provided consultation to Alexion Pharmaceuticals, MedImmune LLC and Chugai Pharma but has received no personal fees or personal compensation for these consulting activities. All compensation for consulting activities is paid directly to Mayo Clinic. TJK is a consultant for SpineThera. DMW has received research support from Alexion, Terumo BCT and the Guthy-Jackson Charitable Foundation, receives financial compensation for participation on a relapse adjudication panel for MedImmune, has served as a consultant to Alexion, MedImmune and Chugai Pharmaceuticals, and has served as co-Editor-in-Chief of The Neurologist.
Ethics approval Institutional Review Board of Mayo Clinic, Rochester, Minnesota.
Provenance and peer review Not commissioned; externally peer reviewed.