Short transverse myelitis (STM; <3 vertebral segments) is considered non-characteristic of neuromyelitis optica (NMO) spectrum disorders (NMOSDs). Non-appreciation of the potential for STM to occur in NMOSD may lead to increased disability from delay in diagnosis and appropriate treatment.
Mayo Clinic researchers conducted a study, recently published in Jama Neurology, to determine the frequency of short lesions at the initial myelitis manifestation of NMOSD and to compare the demographic, clinical, and radiological characteristics of aquaporin-4-IgG (AQP4-IgG) seropositive and seronegative STM.
According to the study, 25 patients who were AQP4-IgG seropositive with an initial STM represented 14% of initial myelitis episodes among patients with NMOSD. The STM episode was defined as the first manifestation of NMOSD in 10 patients (40%) preceded by optic neuritis in 13 patients (52%) and preceded by a nausea and vomiting episode in two patients (8%).
Based on these results, short transverse myelitis is not uncommon in NMOSD and, when it is present, delays diagnosis and treatment. Clinical and radiological characteristics identified in this study may help select patients with STM who are at the highest risk for an NMOSD. Short transverse myelitis does not exclude consideration of AQP4-IgG testing or NMOSD diagnosis.