Short Myelitis Lesions in Aquaporin-4-IgG-Positive Neuromyelitis Optica Spectrum Disorders

Flanagan et al. published a study in 2014 to see how often patients with Neuromyelitis Optica Spectrum Disorders (NMOSD) have an initial attack of short transverse myelitis (STM) rather than longitudinally extensive transverse myelitis (LETM). LETM is a lesion extending more than three vertebral sections, while STM is a lesion that extends no more than three vertebral segments. NMO is characterized by LETM and/or aquaporin-4-IgG positivity, and it is important to catch NMO early in the disease in order to treat properly and reduce long-term disability. While NMO is characterized by LETM, STM often occurs in multiple sclerosis (MS), and it is important to differentiate between a diagnosis of NMO and MS because they have different treatment options, but it is unknown how often STM occurs in AQP4-IgG positive NMO.

The authors reviewed medical records of 319 patients who had AQP4-IgG positive NMO or NMOSD. Of these 319 patients, 25 patients (14%) had an initial attack of STM and had an MRI 90 days or less after this attack, and they were included in the study. They also included 27 control patients with STM who were AQP4-IgG negative. The final diagnoses in the control group were relapsing remitting MS (15 patients), monophasic STM (10 patients) and relapsing STM (2 patients). 83% of the 25 patients who had AQP4-IgG positive NMO or NMOSD made the treating physician unsure that the diagnosis should be NMO because the patients’ lesions were short. Those with STM had a median delay to diagnosis (5 months) that was greater than patients who had LETM (0 months). They also identified some risk factors for NMO or NMOSD, which included non-white race/ethnicity, older age, tonic spasms, history of autoimmunity, centrally located axial T2-hyperintensities and T1-hypointensities, lack of oligoclonal bands, severe or bilateral optic neuritis without good recovery, and long episodes of nausea or vomiting.

Short Transverse Myelitis

Longitudinally Extensive Transverse Myelitis

The authors conclude that short lesions are not uncommon in NMO or NMOSD and neurologists should consider this when diagnosing patients to avoid delaying treatment or giving inappropriate treatment. Dr. Benjamin Greenberg, Director of the TM and NMO centers at University of Texas Southwestern in Dallas, recommends all patients with a diagnosis of TM be tested for AQP4-IgG.