BACKGROUND AND PURPOSE Magnetic resonance imaging (MRI)‐derived spinal cord (SC) gray and white matter (GM/WM) volume are useful indirect measures of atrophy and neurodegeneration over time, typically obtained in the upper SC. Neuropathological evidence suggests that in certain neurological conditions, early degeneration may occur as low as the sacral SC. In this study, the feasibility of GM/WM segmentation of the conus medullaris (CM) was assessed in vivo. METHODS Twenty‐three healthy volunteers (11 female, mean age 47 years) underwent high‐resolution 3T MRI of the CM using a 3‐dimensional fast field echo sequence. Reproducibility of the volume measurements was assessed in 5 subjects (2 female, 25‐37 years) by one rater who repeated the analysis 3 times and also with 2 additional raters working independently in order to calculate the intra‐ and interrater coefficient of variation (COV), respectively. Furthermore, the influence of age, gender, spine and SC metrics on tissue‐specific measures of the CM was investigated. RESULTS Volumetric CM analyses (N = 23) for the SC, GM, and WM revealed a mean (SD) total volume of CM‐TV = 1746.9 (296.7) mm3, CM‐GM‐TV = 731.2 (106.0) mm3, and CM‐WM‐TV = 1014.6 (211.3) mm3, respectively. The intra‐rater COV for measuring the CM‐TV and CM‐GM‐TV was 3.38% and 7.42%, respectively; the interrater COV was 3.43% and 10.80%, respectively. Using age, gender, spine and SC metrics in regression models substantially reduced group variability for CM‐TV, CM‐WM‐TV, and CM‐GM‐TV by up to 39.2%, 42.7%, and 21.2%, respectively. CONCLUSIONS The results from this study demonstrate the feasibility of obtaining tissue‐specific volume measurements in the CM by means of MRI with good reproducibility and provide normative data for future applications in neurological diseases affecting the lower SC.

BackgroundMyelin oligodendrocyte glycoprotein-antibody (MOG-ab)-associated disease (MOGAD) has highly heterogenous clinical and imaging presentations, in which encephalitis is an important phenotype. In recent years, some atypical presentations in MOG-ab-associated encephalitis (MOG-E) have been increasingly reported but have not yet been described well. The aim of the study was to describe the clinical and imaging features of patients with MOG-E in our center. Atypical phenotypes would be reported, which is expected to expand the spectrum of MOGAD.MethodsWe reviewed medical records of 59 patients with MOGAD diagnosed in our center and identified cases who had ever experienced encephalitic symptoms. Three hundred ten patients with autoimmune encephalitis (AE) were also reviewed, and cases with positive MOG-ab were identified. Besides, patients with chronically progressive encephalitis were identified from 13 MOG-E and 310 AE patients. We collected demographic, clinical, laboratory, radiological, and outcome data to explore clinical and imaging characteristics in MOG-E, especially in the atypical phenotype of chronically progressive encephalitis.ResultsWe identified 13 patients (7 males, 6 females) with MOG-E. The median age at onset was 33 years (range 13~62 years). Most (9/13, 69.2%) of patients showed acute or subacute onset of encephalitic symptoms. Brain MRI abnormalities were observed in all patients. The most common lesion locations on MRI were cortical/subcortical (11/13, 84.6%), deep/periventricular white matter (10/13, 76.9%) and corpus callosum (4/13, 30.8%). Brain MRI patterns were categorized into four phenotypes. The most common pattern was cortical encephalitis with leptomeningeal enhancement/brain atrophy (10/13, 76.9%). Eight (8/13, 61.5%) patients had a good response to immunotherapy. Four (4/13, 30.8%) patients with chronically progressive course were identified from MOG-E cohort. They showed leukodystrophy-like pattern, multifocal hazy lesions, or cortical encephalitis on MRI. With immunotherapy, they only showed mild or no improvement. We also identified four (4/310, 1.3%) patients with chronically progressive course from AE cohort. They had better outcomes than counterparts in MOG-E.ConclusionsThis study demonstrates that encephalitic presentations in MOGAD had complex clinical patterns. Chronically progressive encephalitis may be a new phenotype of MOGAD. We recommend to test MOG-ab in subacute and chronic progressive dementia with leukodystrophy-like MRI lesions.

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