Neurologic Presentation of Probable Seronegative Paraneoplastic Encephalitis in a Woman With an Ovarian Teratoma

Autoimmune Encephalitis as a Rare Paraneoplastic Syndrome in Adrenocortical Carcinoma

Paraneoplastic neurologic syndromes (PNSs) are rare in pediatrics and are understood to be consequences of cross-reactivity against various neuroendocrine antigens expressed on cancer cells. Here, we report a case of autoimmune encephalitis, a type of PNS associated with a case of adrenocortical carcinoma (ACC), that had a clinical response to immunosuppressive therapy. ACC is a rare tumor with controversial tissue of origin but expresses various neuroendocrine antigens that could be the possible mechanism for this rare yet interesting association.

Two Cases of Encephalitis without Anti-N-methyl-D-aspartate Receptor Antibody Successfully Treated with Ovarian Teratoma Resection and Immunotherapy

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disorder sometimes accompanied by ovarian teratoma. However, the concept of encephalitis without anti-NMDAR antibodies successfully treated with ovarian teratoma resection and immunotherapy has not been established. We herein report two such cases. Case 1 exhibited delayed magnetic resonance imaging abnormalities in the thalamus and basal ganglia, despite clinical improvement. Case 2 presented with brainstem encephalitis similar to Bickerstaff's encephalitis. Although both patients tested negative for anti-NMDAR antibodies, the recovery of the neurological function and good prognosis following tumor resection with immunotherapy indicated a close association between these diseases and 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.