Question:

What is a teratoma?

Answer:

A teratoma is a tumor that may contain several types of body tissue. A person’s antibody attack on the brain can be a reaction to the presence of an ovarian or testicular teratoma.  The Anti-NMDA receptor encephalitis is associated in some cases with ovarian pathology, in particular teratomas. It is considered, that the antibodies that are attacking (the NR1-NR2 subunits of the NMDA subtype of glutamate receptors) the person’s healthy brain cells, have developed, in response to this abnormal tissue.

 Ovarian tumors, primarily ovarian teratomas occur 59% cases in anti-NMDAr encephalitis. Teratomas are found most commonly in women between age 12 and 45 and in patients in Asian or African American descent. A 2021 case study describes a teratoma in a 4-year-old female child, the youngest case to date. Testicular teratoma is common. Other germ-cell and rarely non-germ cell tumors have also been described in association with anti-NMDA-receptor encephalitis.

 The removal of any identified teratoma takes place first and then first-line immunotherapy treatment typically corticosteroids, intravenous immunoglobulins or plasma exchange is administered. In one series of patients with anti-NMDA-receptor encephalitis, five out of six patients with an ovarian teratoma who did not undergo surgery died. In contrast removal of the tumor may be curative in approximately 80% of patients who undergo tumor removal and immunosuppressive treatment, substantial neurological improvement occurs. Symptoms of anti-NMDA-receptor encephalitis markedly improved within one month of tumor removal and immunosuppressive treatment, though recovery can continue for up to 24 months.

Treatment is generally thought to be more effective in patients who have underlying tumor removed. Cases of ovarian teratomas discovered years after initial onset of symptoms have been described particularly in patients who experienced a slow recovery. A case was reported where oophorectomy was performed despite negative scan results (MRI, abnormal Ultrasound, CT) and on postoperative biopsy an occult teratoma was revealed, was subsequent improvement in clinical symptoms. Patients may require prolonged monitoring for development of teratoma.

Although the younger the patient is, the less likely a tumor will be detected, we still emphasize that all patients with suspected or confirmed anti-NMDAR encephalitis should be screened for ovarian tumors if possible. Prompt initiation
of immunotherapy and tumor removal are crucial for good outcomes.

References:  Anti-N-methyl-D-aspartate receptor encephalitis: review of clinical presentation, diagnosis and treatment 2015. Anti-NMDA-receptor encephalitis: A neuropsychiatric syndrome associated with ovarian teratoma 2015. And Anti-NMDA Receptor Encephalitis by Dr Chris Nickson, last updated April 17, 2019 in Life in the Fast Lane.