Successful Laparoscopic Resection of 7 mm Ovarian Mature Cystic Teratoma Associated with Anti-NMDAR Encephalitis

Anti-NMDAR (N-methyl-D-aspartate receptor) encephalitis is an immune-mediated encephalitis. It has been predominantly described in young women and is commonly associated with an ovarian teratoma. We report a case of anti-NMDAR encephalitis associated with a 7 mm ovarian teratoma that was completely resected by laparoscopic surgery. An 18-year-old woman suddenly presented with personality changes requiring her admission to the department of neurology. After that, she also showed involuntary movements, disturbance of consciousness, and central hypoventilation. As an abdominal image revealed the possibility of a right ovarian teratoma of 5 × 7 mm, a laparoscopic operation was performed. The macroscopic appearance of the right ovary did not show any abnormalities; nevertheless, we performed a partial resection of the right ovary, with reference to the image diagnosis, in order to spare the ovarian reserve. The 22 × 22 mm partially resected ovary contained an intact 5 × 7 mm cystic tumor. The pathological diagnosis was mature cystic teratoma with components of brain tissue. An anti-NMDAR-antibody test proved positive in both serum and cerebrospinal fluid 1 month after the surgery. From these results, she was diagnosed with anti-NMDAR encephalitis. By the administration of cyclophosphamide in addition to the operation, she recovered drastically without any of the symptoms shown before.