Anti-NMDA Receptor Encephalitis or Primary Psychiatric Disorder?

Andrew D. Bowser

May 01, 2020

It remains difficult to distinguish anti-NMDA receptor encephalitis from a primary psychiatric disorder, but recent studies have identified clinical features and proposed screening criteria that could make it easier to identify these patients who would benefit from immunotherapy, according to an expert in the neurologic disease.

Most patients with confirmed anti-NMDA receptor encephalitis will experience substantial improvement after treatment with immunotherapy and other modalities, said Josep Dalmau, MD, PhD, professor at the Catalan Institute for Research and Advanced Studies at the University of Barcelona and adjunct professor of neurology at the University of Pennsylvania, Philadelphia.

"In our experience, being aggressive with immune therapy...the patients do quite well, which means that basically 85%-90% of the patients substantially improved over the next few months," Dr. Dalmau said at the annual meeting of the American Psychiatric Association, which was held as a virtual live event.

Identified for the first time a little more than a decade ago, anti-NMDA receptor encephalitis is a rare, immune-mediated disease that is usually found in children and young adults and is more common among women. It is frequently associated with ovarian tumors and teratomas, said Dr. Dalmau, and in about 90% of cases, patients will have prominent psychiatric and behavioral symptoms.

Patients develop IgG antibodies against the GluN1 subunit of the NMDA receptor. These autoantibodies represent not only a diagnostic marker of the disease, but are also pathogenic, altering NMDA receptor–related synaptic transmission, Dr. Dalmau said.

In several recent studies, investigators have attempted to cobble together a distinct phenotype on anti-NMDA receptor encephalitis to aid psychiatrists who might encounter patients with the disease, he said.

In one of the most recent studies, researchers combed the medical literature and found that, among 544 individuals with the disease, the most common psychiatric symptoms were agitation, seen in 59%, and psychotic symptoms (particularly visual-auditory hallucinations and disorganized behavior) in 54%; catatonia was seen in 42% of adults and 35% of children.

Several "red flags" could tip off clinicians to a diagnosis of anti-NMDA receptor encephalitis, according to a report from researchers in Berlin, Dr. Dalmau added. By picking up on those clinical signs, which included seizures, catatonia, autonomic instability, or hyperkinesia, the time from symptom onset to diagnosis could be cut in half, the researchers found.

There's also a handy acronym that could serve as a mnemonic to pick up on "diagnostic clues" of anti-NMDA receptor encephalitis among patients with new-onset psychiatric symptoms, Dr. Dalmau said.

That acronym, published in a review article by Dr. Dalmau and colleagues, is SEARCH For NMDAR-A, covering, in order: sleep dysfunction, excitement, agitation, rapid onset, child and young adult predominance, history of psychiatric disease (absent), fluctuating catatonia, negative and positive symptoms, memory deficit, decreased verbal output, antipsychotic intolerance, rule out neuroleptic malignant syndrome, and of course, antibodies (though the final "A" also stands for additional testing, including magnetic resonance imaging, cerebrospinal fluid studies, and electroencephalogram).

While the disease can be lethal, Dr. Dalmau said most patients respond to immunotherapy, and if applicable, treatment of the underlying tumor can help. The most common first-line treatments include steroids, intravenous immunoglobulin, and plasma exchange, he said, while second-line treatments include the monoclonal anti-CD20 antibody rituximab and cyclophosphamide.

Beyond immunotherapy, patients may benefit from supportive care and psychiatric treatment. Benzodiazepines are well tolerated, but Dr. Dalmau said antipsychotic intolerance is frequent, and electroconvulsive therapy has "mixed results" in these patients.

The recovery process can take months and may be complicated by hypersomnia, hyperphagia, and hypersexuality, he added.

"Some patients improve dramatically in 1 month, but this is uncommon, really," he said, adding that an early recovery may be a "red flag" that the underlying condition is something other than anti-NMDA receptor encephalitis.

Dr. Dalmau provided disclosures related to Cellex Foundation, Safra Foundation, Caixa Health Project Foundation, and Sage Therapeutics.

SOURCE: Dalmau J. APA 2020, Abstract

This article originally appeared on MDedge.com.

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