Ovarian Teratoma or Uterine Malformation? PET/MRI as a Novel Useful Tool in NMDAR Encephalitis.

This is a case report of a 17-year-old girl affected by N-methyl-D-aspartate-receptor (NMDAR) encephalitis suspected for a paraneoplastic syndrome. Ultrasound (US) and computed tomography (CT) imaging identified an ovarian lesion compatible with teratoma. 18F-fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET/MRI), performed to evaluate metabolic activity of the brain and of the ovarian mass, correctly changed the diagnosis to uterine malformation that was later histologically proven.