EGADS! A Zebra Among Horses!


Sky Prestowitz, Kevin Patel, MD, David Chen, MD


This case highlights the importance of maintaining high suspicion for autoimmune encephalitis in patients with rapidly progressing psychosis. While advanced immunologic testing has added autoimmune encephalitis to the differential diagnosis for altered mental status it can be diagnosed with traditional methods. Due to the delicate nature of brain tissue, timely diagnosis and treatment can make a marked difference in quality of life.

Case Presentation

This 27-year old man with past medical history of epilepsy and schizophrenia presented to the emergency department with marked behavior changes over one month including increased hallucinations, agitation, and suspected seizure activity. The patient was diagnosed with intellectual disability as a child, epilepsy at 16, and schizophrenia at 25. Family and home health aides brought him to the emergency department several times in two weeks prior to his admission with concern for his worsening condition. On exam the patient was unable to answer questions. He exhibited confusion and echolalia. Cranial nerves were grossly intact. He was able to move all four extremities spontaneously without gross asymmetry. Deep tendon reflexes were 1+ and symmetric. Proprioception, cerebellar, and testing involving command following was limited otherwise no focal neurologic deficits noted. The patient had no lymphadenopathy, rash, or fever and no evidence for myalgia, nausea, or headache. In the emergency department electrolytes, liver function tests, and ammonia levels were normal. Urine drug screen was negative. Thyroid stimulating hormone was elevated, but T4 was normal. Computed tomography of the brain was negative for structural processes including hemorrhage. Over two weeks, the patient's agitation worsened, magnetic resonance imaging (MRI) revealed diffuse abnormal enhancement in bilateral cerebellar hemispheres suggestive of encephalitis. During 24-hour electroencephalogram (EEG) monitoring the patient had status epilepticus and was transferred to the neurology intensive care unit. Lumbar puncture was performed and cerebrospinal fluid (CSF) was tested for 15 different common viral, bacterial, and fungal causes of infectious encephalitis; all were negative. CSF antibody testing showed positive glutamic acid decarboxylase-65 antibodies establishing diagnosis of anti-glutamic acid decarboxylase-65 autoimmune encephalitis. The patient was treated with pulse dosed steroids, intravenous human immunoglobulin, rituximab, and plasmapheresis. The acuity of his situation decreased dramatically but did not return to cognitive baseline.


Autoimmune encephalitis is an important consideration in cases of altered mental status and traditional methods can be used to diagnose it. Careful history can elicit subacute disease progression of symptom worsening and mixed features including psychosis, agitation, and speech dysfunction. Traditional methods such as basic metabolic panel, CSF polymerase chain reaction with culture, and urine drug screen rule out common infections, electrolyte abnormalities, and toxic ingestions. Computed tomography can rule out gross structural abnormalities. More specific indicators include brain MRI and EEG. Suggestive brain MRI findings include hyperintense signal on T2 weighted sequences highly restricted to one or both medial temporal lobes. Other MRI findings include multifocal areas involving grey matter, white matter, or both compatible with demyelination or inflammation. Suspicious EEG findings include generalized slowing, subclinical seizures, and non-convulsive status epilepticus. Antibody testing can establish the specific autoimmune process to guide further management.


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