Longitudinally Extensive Transverse Myelitis Causes and Diagnostic Approach

Primary Autoimmune/Inflammatory Causes

The primary causes of LETM are MOG-antibody associated encephalomyelitis (MOG-EM) and aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD), which together account for the majority of cases 1, 2
MOG-antibody associated encephalomyelitis (MOG-EM) is common in LETM, occurring in approximately 44-52% of patients at some point during their disease course 1, 3
In pediatric MOG-EM patients, LETM is frequently present at disease onset (80% in examined cases) 1
Aquaporin-4 antibody-positive NMOSD is characterized by LETM extending ≥3 vertebral segments, a hallmark feature and diagnostic criterion for AQP4-NMOSD 1, 2
Multiple sclerosis (MS) rarely if ever occurs in LETM; when present, it should prompt consideration of alternative diagnoses 1, 2

Acute disseminated encephalomyelitis (ADEM) can present with LETM, particularly in pediatric populations, often with concurrent brain involvement 4

When evaluating LETM, immediately test for both AQP4-IgG and MOG-IgG antibodies in parallel if cost is not prohibitive; if cost is a factor and the disease is stable, test AQP4-IgG first as it is more frequent 1, 3
CSF analysis showing neutrophilic pleocytosis or WCC >50/μl suggests MOG-EM or AQP4-NMOSD rather than MS 2, 4
Absence of oligoclonal bands (in 87-88% of MOG-EM patients) also distinguishes from MS 5
Conus medullaris involvement is particularly suggestive of MOG-EM, especially at disease onset 4