Abstract
Anti-N-methyl-D-aspartate receptor encephalitis is an auto-immune paraneoplastic disease of the limbic system. This syndrome may present itself as a range of psychiatric, neurological and autonomic features. It is associated with long-term morbidity and mortality. The syndrome is associated with ovarian teratoma affecting mainly young females. If the syndrome is identified at an early stage, then a good prognosis is expected. In this case report, the ultrasound performed by an experienced and competent operator was more sensitive than MRI in diagnosing a small ovarian teratoma. Following the removal of the teratoma and with appropriate immunotherapy the patient's condition improved. In the clinical suspicion of anti-A-methyl-D-aspartate receptor encephalitis, the first modality of choice should be an ultrasound of the ovaria performed by an experienced and competent operator.