Electrophysiological Findings in Neuromyelitis Optica Spectrum Disorder

Neuromyelitis Optica Spectrum Disorder (NMOSD) has been differentiated from Relapsing Remitting Multiple Sclerosis (RRMS) by clinical, laboratory, and pathological findings, including the presence of the anti-aquaporin 4 antibody. However, it is recognized that patients with NMOSD are hard to differentiate from those with RRMS. Measurement of Evoked Potentials (EPs) is often used to diagnose RRMS and to find subclinical lesions in patients with RRMS, but EPs have not been investigated in detail in patients with NMOSD. Here, we have compared EPs in patients with NMOSD to those with RRMS. Characteristic findings in patients with NMOSD were the absence of both visual evoked potentials and of motor evoked potentials in the lower extremities, while in patients with RRMS there were delays in these potentials. Most patients with NMOSD did not present abnormal subclinical EPs, whereas many patients with RRMS did. None of the patients with NMOSD showed abnormalities in auditory brainstem responses. These data lead us to conclude that NMOSD can be differentiated from RRMS by EP data obtained in the early stages of these diseases.