Another indication is the presence of new seizures within 1 year of presenting with psychotic symptoms.10 The possibility of undiagnosed seizures should be considered in a patient with psychosis who has episodes of unresponsiveness, dissociative episodes, or seizure-like activity that is thought to be psychogenic but has not been fully evaluated. Seizures in autoimmune encephalitis involve deep structures in the brain and can be present without overt epileptiform activity on EEG, but rather causing only bilateral slowing that is often described as nonspecific.12
In a young patient presenting with first-episode psychosis, a recent diagnosis of cancer or abnormal finding in the ovaries increases the likelihood of autoimmune encephalitis.4 Historically, however, this type of medical history has been irrelevant to psychosis. Although rare, any person presenting with first-episode psychosis and a history of herpes simplex virus (HSV) encephalitis should be evaluated for autoimmune encephalitis because anti-NMDA receptor antibodies have been reported to be present in approximately one-third of these patients.13 Finally, the report of focal neurologic symptoms, including neck stiffness or neck pain, should raise concern, although sensory, working memory, and cognitive deficits may be difficult to fully distinguish from common somatic and cognitive symptoms in a primary psychiatric presentation.
Table 1 lists 4 questions to ask patients who present with first-episode psychosis that may not usually be part of a typical evaluation.
CASE CONTINUED
Uncooperative with examination
In the ED, Ms. L’s heart rate is 101 beats per minute and her blood pressure is 102/72 mm Hg. Her body mass index (BMI) is 22, which suggests an approximate 8-pound weight loss since her BMI was last assessed. Ms. L responds to questions with 1- to 6-word sentences, without clear verbigeration. Though her speech is not pressured, it is of increased rate. Her gaze scans the room, occasionally becoming fixed for 5 to 10 seconds but is aborted by the interviewer’s comment on this behavior. Ms. L efficiently and accurately spells WORLD backwards, then asks “Why?” and refuses to engage in further cognitive testing, stating “Not doing that.” When the interviewer asks “Why not?” she responds “Not doing that.” Her cranial nerves are intact, and she refuses cerebellar testing or requests to assess tone. There are no observed stereotypies, posturing, or echopraxia.
While not necessary for a diagnosis of autoimmune encephalitis, short-term memory loss is a common cognitive finding across studies.5-7 A common clinical finding from a mental status exam is speech disorders, including (but not limited to) increased rates of speech or decreased verbal output.7 Autonomic instability—including tachycardia, markedly labile blood pressures, and orthostasis—all increase the likelihood of autoimmune encephalitis.14 Interpreting a patient’s vital sign changes can be confounded if they are agitated or anxious, or if they are taking an antipsychotic that produces adverse anticholinergic effects. However, vital sign abnormalities that precede medication administration or do not correlate with fluctuations in mental status increase suspicion for an autoimmune encephalitis.
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