Precipitously and certainly psychotic—but what’s the cause?

At discharge, Ms. L’s clinical presentation is thought to be most consistent with viral encephalitis, because of her CSF lymphocytic pleocytosis, fever, and improvement with supportive care. Because she improves, the team does not find it necessary to wait for results of pending studies, including a paraneoplastic autoantibody panel and a CSF anti-NMDA receptor antibody, before discharging her.

Readmission. Although the results of the paraneoplastic autoantibody panel are unremarkable, several weeks after discharge Ms. L’s CSF anti-NMDA receptor antibodies return positive, despite 2 earlier negative serum studies. She is readmitted to the neurology service for treatment with immunomodulators.

A positron-emission tomography scan is negative for malignancy. She is treated on an ongoing basis with immunomodulators; cognition improves such that she is able to start working again with good overall functioning. Despite this improvement, she experiences residual sequelae, including noise sensitivity, amnesia of the events surrounding her hospitalization, mild short-term memory deficits, and persistent affective blunting.

The authors’ observations
Psychosis is not exclusive to psychiatric syndromes and frequently is a symptom of an underlying neurologic, immunologic, metabolic, infectious, or oncologic abnormality.¹ Anti-NMDA receptor encephalitis is an autoimmune disease in which antibodies attack NMDA-type glutamate receptors at central neuronal synapses and can produce psychosis, as seen with Ms. L² (Table 1^2,3). The etiology of the disease is not fully understood. Determining the appropriate setting to perform a complete medical workup in a severely agitated patient after an initial negative medical workup can be challenging.

What’s the most appropriate treatment setting?
This case illustrates the importance, with any new-onset psychosis, of weighing heavily a carefully obtained psychiatric history, even in the absence of focal physical examination and initial laboratory abnormalities. It also highlights the challenge of determining the most appropriate initial setting for performing the important task of a complete medical workup for first-episode psychosis.

Ms. L initially was treated in the inpatient psychiatric unit because of safety concerns and practical limitations, but was later found to have a disease that could not be managed in that setting. She proved to be too agitated to obtain a full medical workup on the inpatient psychiatric or general medical floors and required transfer to the ICU. Despite her normal basic laboratory tests, her EEG and CSF studies did demonstrate abnormalities, suggesting these can be useful to the basic workup for psychosis of unknown cause (Table 2^1,2).

This case also demonstrates that negative serum anti-NMDA receptor antibody tests do not rule out the disease; one study found that only 85% of patients with CSF anti-NMDA receptor antibodies also had detectable antibodies in their serum and that detectability changed during the course of the disease.⁴ This supports the utility of a lumbar puncture as part of a basic initial workup for some cases of new-onset psychosis. Because clinical outcomes often correlate with early treatment, as with anti-NMDA receptor encephalitis, a timely diagnostic workup of psychosis often can be important.^3,5 The ICU can be considered an appropriate setting for working up some patients who develop new, rapid-onset psychosis and severe agitation, even in the absence of initial laboratory or physical examination findings.

Ms. L’s case also illustrates the importance of completing a thorough medical workup for patients with new-onset psychosis before transferring them to an independent psychiatric hospital. Initially, the university’s psychiatric unit was at capacity and a bed was sought at outside psychiatric hospitals while Ms. L waited in the ED. Had Ms. L not been admitted to a large academic medical center, she may not have had access to the multidisciplinary collaboration that proved necessary for the appropriate diagnosis and treatment of her anti-NMDA receptor encephalitis (Table 3^5,6).

What prodromal symptoms occur as long as 2 weeks as an initial presentation in many patients with anti-NMDA receptor encephalitis?
   a) Flu-like symptoms of lethargy, headache, gastrointestinal symptoms, myalgias, fevers, and upper respiratory symptoms
   b) Delusions, hallucinations, disorganized behaviors and thoughts, behavioral outbursts, hypersexuality, mood lability, personality change, paranoia, echolalia, mutism, anxiety, agitation, aggression, hyperactivity, sleep dysfunction, and blunted affect
   c) Dyskinesias, autonomic instability, central hypoventilation, and seizures

The authors’ observations
Lab results, vital signs, and physical examination should not supplant a careful history when determining an appropriate clinical course of action. As experts in the cognitive sciences, psychiatrists may be the most qualified in determining whether a patient with new-onset psychosis should undergo further medical testing before a condition is deemed to be solely of a psychiatric cause. As a neurologic disease of immunologic origin with psychiatric manifestations, anti-NMDA receptor encephalitis is a complex condition requiring collaboration among several specialists for appropriate management.