Longitudinally extensive transverse myelitis: Etiologies and common diagnostic pitfalls

report the different etiologies of Longitudinally Extensive Transverse Myelitis (LETM), along with their key characteristics. A retrospective study was conducted at Hotel-Dieu de France University Hospital, Beirut, Lebanon. We collected demographic, clinical, radiologic and biochemical data of patients admitted for LETM between January 2021 and September 2024. Patients with compressive myelopathy or missing data were excluded. LETM characteristics were described in the whole sample, as well as in patients with inflammatory myelitis and those with spinal dural arteriovenous fistula (SDAVF). 32 patients were selected, of whom 12 patients were excluded. The most common cause of LETM was SDAVF (25%), followed by MOG antibody-associated disease, multiple sclerosis, idiopathic transverse myelitis, neurosarcoidosis and infectious myelitis (10% each). There was only one case of Neuromyelitis Optica Spectrum Disorder (NMOSD). Other causes included MOG-negative acute disseminated encephalomyelitis, paraneoplastic myelitis, spinal cord neoplasm and subacute combined degeneration of spinal cord (5% each). In total, there were 13 cases of inflammatory myelitis (65%). Patients with SDAVF were predominantly males (80%) and relatively older than those with inflammatory myelitis. Different MRI patterns were described: all inflammatory LETM involved cervical and/or thoracic cord, 69% were partial and enhanced on postcontrast sequences. Vascular myelopathy affected thoracolumbar region in 80% of cases. Perimedullary flow voids were common (80%) but inconsistent. Neurologist should think beyond NMOSD in case of LETM. The presence of thoracolumbar LETM with or without perimedullary flow voids requires MR angiography, before diagnostic lumbar puncture or empirical steroid therapy.