Background: Anti-N-methyl-D-aspartate receptor [anti-NMDAR] encephalitis is an autoimmune encephalitis commonly associated with ovarian teratoma [OT]. Currently, there is no literature for anti-NMDAR encephalitis in Thai patients who may have different clinical manifestations compared to patients from other regions.

Objective: To evaluate the clinical characteristics, assessments, and outcomes of a series of anti-NMDAR encephalitis in Thai patients and review of the literature.

Materials and Methods: All adult Thai patients with anti-NMDAR encephalitis confirmed positive by one anti-NMDAR antibody test, either in serum or cerebrospinal fluid [CSF], and hospitalized in the Department of Medicine, Siriraj Hospital, Thailand, between 2007 and 2016, were identified from the hospital’s database.

Results: Nine patients with a median age of 21 years (range 15 to 49), including eight (89%) that were female, were included in this study. Initial presentations included seizures (4 patients, 44%), psychiatric symptoms (4, 44%), and cognitive impairment (1, 11%). Chronic relapsing inflammatory optic neuropathy proceeded to encephalopathy in one patient (11%). Six patients (67%) had abnormalities in brain imaging, revealed by computed tomography with contrast or magnetic resonance imaging, or both. Leptomeningeal enhancement was present in two patients (22%). An OT was found in three out of six patients (50%), all of whom underwent tumor removal. Immunotherapy was given to all patients. Clinical outcomes were marked recovery in four patients (44%), persistent cognitive deficit and partial dependency in two (22%), and death by hospital-acquired pneumonia in two (22%).

Conclusion: The majorities of the initial manifestations of anti-NMDAR encephalitis in the Thai patients were seizures and psychiatric symptoms. The first episode of seizure without other neurological abnormalities especially among young adult women may reveal anti-NMDAR encephalitis. CRION may precede such an encephalitis. Leptomeningeal enhancement, with or without intraparenchymal lesion, may be more frequently seen in Thai patients.

Keywords: Anti-NMDAR encephalitis, Thai, Seizure, Leptomeningeal enhancement, CRION, Recurrent optic neuritis