Anti-NMDA Receptor Encephalitis
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Anti-NMDA receptor encephalitis
Overview
- Anti-NMDA receptor encephalitis is one of the most common forms of autoimmune encephalitis and is especially common in young woman.
- While it can occur in the setting of ovarian teratoma (in which case it is considered paraneoplastic), the syndrome often occurs in the setting of no neoplastic trigger.
Pathophysiology
- The NMDA receptor acts as a cell surface antigen and antibodies target an epitope at the N-terminal domain of the NR1 subunit of the NMDA receptor.
- Autoantibodies to extracellular antigens are characteristically easier to treat than autoantibodies to intracellular antigens.
- For anti-NMDA receptor encephalitis, draw a neuronal junction.
Clinical Presentation
- There is often a progression from a flu-like illness for several days to a profoundly severe psychotic phase with delusions, agitation and disinhibition, paranoid hallucinations, and even catatonia; the presentation is so severe it is often mistaken for psychiatric illness.
- In addition to psychosis, there is cognitive dysfunction and the disease may progress to involve motor dyskinesias, autonomic instability, and seizures.
Diagnostic Testing
CSF Testing
- CSF testing can reveal a mild lymphocytic pleocytosis (mildly elevated WBC that is predominantly lymphocytes), a mild elevation in CSF protein, and the presence of oligoclonal bands (immunoglobulins found in the CSF but not the serum).
Serologies
- Anti-NMDA receptor testing in CSF is more sensitive than in serum, which can be falsely negative in at least ~ 15% of cases (85% sensitivity), so testing both fluids is recommended.
MRI
- MRI, however, is often normal (or displays mild, varied hyperintensities) and EEG is often nonspecific (with just slowing).
Ovarian Teratoma
- Ovarian teratomas are the most common germ cell neoplasm and are a key paraneoplastic antibody cause of anti-NMDA receptor encephalitis.
- Remarkably they can comprise mature tissues, such as bone, teeth, eyes and other nervous system tissues, muscle, hair, and other tissue types.
Ovarian Teratoma Gross Section
- Teratoma Image adapted from Ed Uthman from Houston, TX. Mature Cystic Teratoma of the Ovary Uploaded by CFCF.