Rate of Anti-NMDA Receptor Encephalitis in Ovarian Teratomas

Background The rate of anti-N-methyl-D-aspartate receptor encephalitis (NMDARE) in ovarian teratomas is unknown. We aim to identify the prevalence of NMDARE as well as volumetric and histopathologic characteristics of ovarian teratomas in patients with versus without. Methods We performed a retrospective cohort study to identify patients with confirmed ovarian teratomas and the characteristics of teratomas in NMDARE compared with non-NMDARE patients. Patients aged between 0 and 21 years with confirmed histopathological diagnosis of ovarian teratoma after resection were included. The rate of NMDARE in ovarian teratomas was identified. Moreover, volumes of ovarian teratomas and the frequency of neuronal glial elements on histopathology in NMDARE versus non-NMDARE patients were assessed. Results Five out of one-hundred-and-sixty-three (3.07%) patients with histopathology confirmed ovarian teratomas were diagnosed with NMDARE. Age was not different between the NMDARE (mean: 13.8 years, standard deviation: 3.9) and non-NMDARE groups (median: 14, interquartile range [IQR]: 5). Teratoma volumes from NMDARE patients were smaller than those of non-NMDARE patients (median 28.3 cm (3) with IQR of 431.2 and median 182.8 with IQR of 635.0, respectively). Both age and NMDARE diagnosis were statistically significant variables in the analysis of variance on a multiple linear regression model. Age ( p = 0.013) had a positive correlation with teratoma size, whereas presence of NMDARE had a negative correlation ( p = 0.008). Conclusion The rate of NMDARE in ovarian teratomas is low and NMDARE patients have smaller teratomas than non-NMDARE. Further studies are needed to understand the timing of anti-NMDA receptor antibodies in teratomas and the development of NMDARE.