A rare and challenging case of teratoma associated Anti-NMDA receptor encephalitis

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disease that is often underdiagnosed due to the variability and complexity of its clinical presentation and is frequently misdiagnosed as viral encephalitis. It is sometimes characterized as a form of limbic encephalitis, which predominantly affects children and younger adults, with a female-to-male ratio of 4:1. The neurological disease is commonly associated with an underlying tumour. Its pathophysiology is attributed to the formation and binding of IgG1 and G3 antibodies to the NR1 subunit of the NMDA receptor in the central nervous system. We present the case of a 23-year-old woman with a one-year history of episodic mood lability and psychosis who sought medical attention at the emergency department due to the sudden onset of agitation, hallucinations, and altered mental status. Brain magnetic resonance imaging revealed findings suggesting possible encephalitis. A cerebrospinal fluid analysis was positive for NMDAR antibodies, and a transvaginal ultrasound later revealed a right ovarian mass, from which a biopsy confirmed a mature cystic teratoma. Despite surgical resection of the tumour and medical treatment, the patient experienced persistent cognitive impairment and gait dysfunction following three months of hospitalization in the neuroscience intensive care unit. In light of the complexity and aggressiveness of the clinical symptoms of NMDAR encephalitis, the disease has a relatively good prognosis, especially following surgical resection of the associated malignancy and medical treatment in most patients. On the other hand, a delay in diagnosis and treatment may result in long-term functional deficits and poorer clinical outcomes.