Identifying specific myelopathy etiologies in the evaluation of suspected myelitis: A retrospective analysis

Background: Myelopathies require prompt etiologic diagnosis. We aimed to identify a specific myelopathy diagnosis in cases of suspected myelitis to highlight clinicoradiologic differences. Methods: In this retrospective, single-centre cohort of subjects with suspected myelitis referred to London Multiple Sclerosis (MS) Clinic between 2006 and 2021, we identified those with MS and reviewed the remaining charts for etiologic diagnosis based on clinical, serologic, and imaging details. Results: Of 333 included subjects, 318/333 (95.5%) received an etiologic diagnosis. Most (274/333, 82%) had MS or clinically isolated syndrome. Spinal cord infarction (n = 10) was the commonest non-inflammatory myelitis mimic characterized by hyperacute decline (n = 10/10, 100%), antecedent claudication (n = 2/10, 20%), axial owl/snake eye (n = 7/9, 77%) and sagittal pencillike (n = 8/9, 89%) MRI patterns, vertebral artery occlusion/ stenosis (n = 4/10, 40%), and concurrent acute cerebral infarct (n = 3/9, 33%). Longitudinal lesions were frequent in aquaporin-4-IgG-positive neuromyelitis optica spectrum disorder (AQP4+NMOSD) (n = 7/7, 100%) and myelin oligodendrocyte glycoprotein-IgG-associated disorder (MOGAD) (n = 6/7, 86%), accompanied by bright spotty (n = 5/7, 71%) and central-grey-restricted (n = 4/7, 57%) T2-lesions on axial sequences, respectively. Leptomeningeal (n = 4/4, 100%), dorsal subpial (n = 4/4, 100%) enhancement, and positive body PET/ CT (n = 4/4, 100%) aided the diagnosis of sarcoidosis. Spondylotic myelopathies had chronic sensorimotor presentations (n = 4/6, 67%) with relative bladder sparing (n = 5/6, 83%), localizable to sites of disc herniation (n = 6/6, 100%). Metabolic myelopathies showed dorsal column or inverted 'V' sign (n = 2/3, 67%) MRI T2abnormality with B12 deficiency. Conclusions: Although no single feature reliably confirms or refutes a specific myelopathy diagnosis, this study highlights patterns that narrow the differential diagnosis of myelitis and facilitate early recognition of mimics.