A 29-year-old woman with no known past medical history is admitted to the ICU with status epilepticus. Her family reports that she complained of headaches, fevers, and myalgias that started a few days prior to presentation. On exam, you notice abnormal movements of her lips and mouth, but no evidence of seizure activity on EEG. A brain MRI is unremarkable. CSF obtained via lumbar puncture was notable for 14 WBCs, no RBC, mildly elevated protein, and normal glucose. CSF culture is negative and PCR for HSV is also negative. Anti-NMDA antibody in the CSF and serum is positive.
What is the MOST appropriate next step to make a diagnosis?
A. Repeat brain MRI to assess for progression of the diseaseCorrect Answer: D
The patient described has an anti-NMDA receptor antibody–mediated encephalitis. The usual presentation is subacute (3 months) progressive neurological symptoms, which could include new psychiatric symptoms, movement disorders, and new onset seizures. MRI will characteristically show T2 abnormalities, but these are not necessary for the diagnosis. Imaging is needed more for exclusion of other causes (option A is incorrect). The CSF profile could be consistent with primary CNS malignancies; however, CNS malignancies are usually accompanied by specific imaging findings, and not by a positive anti- NMDA receptor antibody (option B is incorrect). As part of the autoimmune encephalitis workup, it is important to rule out systemic autoimmune diseases. However, in this specific case, there are no other signs or symptoms of SLE, and the patient has marker for autoimmune encephalitis (option C is incorrect).
Anti-NMDA receptor encephalitis is the first specific autoantibody described for CNS paraneoplastic syndrome. The most common associated neoplasm, especially given the young age, is an ovarian teratoma (option D is correct).
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