Anti-n-Methyl-d-Aspartate-Receptor (NMDAR) Encephalitis in Association with Ovarian Teratoma

Ovarian Teratoma-Related Paraneoplastic Neurological Syndromes

Paraneoplastic neurological syndromes (PNSs) are a group of neurological disorders triggered by an underlying remote tumor. Ovarian teratoma (OT) is the most common histologic type of germ cell tumor in females. The most common PNSs associated with OT is anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. However, with the increasing number of new antibodies reported over the last decade, the clinical spectrum of OT-related PNSs is also expanding. Our knowledge of OT-related PNSs is still far from complete. Here, we provide a comprehensive review of the most recent findings in the field of OT-related PNSs, with a particular focus on their clinical and pathological characteristics. Overall, the description of neuronal antibodies in PNSs associated with OT strongly suggests that antibodies may be responsible for the clinical symptoms in some cases. OT-related PNSs are associated with various clinical manifestations, including anti-NMDAR encephalitis, limbic encephalitis, encephalomyelitis, progressive cerebellar syndrome and opsoclonus-myoclonus syndrome. The pathological characteristics of the OT suggest that the mechanism of PNSs is probably due to heteromorphic neurons in the tumor tissue, the ectopic expression of the antigens in neural tissue within the teratomas and patients' unusual immune response. Despite the severity of the neurological syndromes, most patients with OT-related PNSs showed good neurologic response to early tumor resection combined with immunotherapy. To further advance the management of OT-related PNSs, additional studies are needed to explore this complex topic.

The Association of Ovarian Teratoma and Anti-N-Methyl-D-Aspartate Receptor Encephalitis: An Updated Integrative Review

Ovarian teratomas are by far the most common ovarian germ cell tumor. Most teratomas are benign unless a somatic transformation occurs. The designation of teratoma refers to a neoplasm that differentiates toward somatic-type cell populations. Recent research shows a striking association between ovarian teratomas and anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis, a rare and understudied paraneoplastic neurological syndrome (PNS). Among teratomas, mature teratomas are thought to have a greater relevance with those neurological impairments. PNS is described as a neurologic deficit triggered by an underlying remote tumor, whereas anti-NMDAR encephalitis is characterized by a complex neuropsychiatric syndrome and the presence of autoantibodies in cerebral spinal fluid against the GluN1 subunit of the NMDAR. This review aims to summarize recent reports on the association between anti-NMDAR encephalitis and ovarian teratoma. In particular, the molecular pathway of pathogenesis and the updated mechanism and disease models would be discussed. We hope to provide an in-depth review of this issue and, therefore, to better understand its epidemiology, diagnostic approach, and treatment strategies.

Brain astrocytoma misdiagnosed as anti-NMDAR encephalitis: a case report

Background

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis, which is the most common type of autoimmune encephalitis, is caused by the production of autoantibodies against NMDA receptor. Anti-NMDAR encephalitis patients present with various non-specific symptoms, such as abnormal psychiatric or behaviour, speech dysfunction, cognitive dysfunction, seizures, movement disorders, decreased level of consciousness, and central hypoventilation or autonomic dysfunction.

Case presentation

A 67-year-old man presented with new-onset focal seizures. The brain magnetic resonance imaging (MRI) plain scan and enhanced scan showed abnormal signal on the proximal midline frontoparietal junction region. Anti-NMDAR antibody was detected in cerebrospinal fluid (CSF) and serum using a commercial kit (Euroimmune, Germany) by indirect immunofluorescence testing (IIFT) according to the manufacturer’s instructions for twice. Both of the test results were positive in CSF and serum. The patient was diagnosed as anti-NMDAR encephalitis and then was treated repeatedly with large dose of intravenous corticosteroids and gamma globulin. Accordingly, the refractory nature of seizures in this case may be attributed to NMDAR autoantibodies. When the patient presented at the hospital for the third time, the brain MRI revealed an increase in the size of the frontal parietal lesion and one new lesion in the left basal ganglia. The patient underwent a surgical biopsy and astrocytoma was confirmed by histopathology.

Conclusions

Although the sensitivity and specificity of anti-NMDAR-IgG antibodies in CSF to diagnose anti-NMDAR encephalitis are close to 100%, it is not absolute. Anti-NMDAR antibodies were positive, which might make the diagnosis more complex. The diagnosis of atypical presentation of anti-NMDAR encephalitis requires reasonable exclusion of other disorders.