"NMDA receptor spectrum disorder" in the differential diagnosis of demyelinating disorders of the CNS: optic neuritis and myelitis

Objective The aim of this study was to investigate the frequency of anti-N-methyl-D-aspartate receptor (anti-NMDAR) antibody positivity in patients presenting with transverse myelitis (TM) and/or optic neuritis (ON), to describe their neurologic and radiological characteristics, and to compare these characteristics with those reported in previous studies. Material and methods This study included 179 patients (ON: 96, TM: 74, ON and TM: 9) who visited Isfahan Multiple Sclerosis Center from January 2017 to September 2019, for approximately 32 months. The respective neurological examinations were performed. Demographic data of the patients, as well as findings from radiological and serological investigations were obtained. Results Frequencies of anti-NMDAR seropositivity in patients with TM, ON, and concurrent TM and ON were approximately 3.4%, 1.4%, and 11.1%, respectively. None exhibited any psychiatric symptoms. Conclusion Based on the frequency of seropositivity for anti-NMDAR antibody in our patients, positivity for this antibody appears to be more frequent than previously anticipated in patients presenting with these conditions. We recommend that the anti-NMDAR antibody presence in CSF/serum be checked and considered in addition to the routine examinations performed upon confronting demyelinating conditions such as TM and ON. We suggest considering the term "NMDAR spectrum disorder" to more clearly distinguish the potentially overlapping conditions with different etiologies in patients with CNS disorders.