SHM Converge Scientific Abstract ePoster Gallery-Mixed Messages: A Case of Autoimmune Encephalitis

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This case highlights the diagnostic challenge of autoimmune encephalitis (AE), especially when antibody testing is negative and symptoms are nonspecific. AE can present with subacute confusion, memory loss, mood change, or seizures, and routine labs, CSF, EEG, and imaging may be normal or only mildly abnormal. Because antibody testing has limited sensitivity, results may take weeks, and many patients have antibody-negative disease, diagnosis must rely heavily on clinical suspicion and exclusion of alternative causes.<br /><br />The patient was a 66-year-old man with a 2–3 month history of brief episodic altered sensorium, paresthesias, speech arrest, and déjà vu, with worsening fatigue and memory impairment. Initial workup showed mild leukocytosis but otherwise unremarkable labs and ECG. CT head and CTA were negative. EEG showed intermittent right hemispheric slowing without seizures. MRI brain demonstrated right mesial temporal lobe edema and enhancement, raising concern for encephalitis. Empiric acyclovir was started for possible HSV encephalitis. Lumbar puncture later showed elevated CSF protein with lymphocytic predominance, but infectious studies were negative, including HSV. Extensive serum and CSF antibody testing was also negative. CT abdomen/pelvis and echocardiogram did not reveal malignancy or another cause.<br /><br />Continuous EEG later showed right temporal slowing, and the patient’s events were felt to be likely temporal lobe auras. Repeat MRI showed improvement in the right mesial temporal abnormalities, supporting limbic encephalitis rather than tumor or ongoing infection. Based on Graus criteria, he was diagnosed with probable antibody-negative limbic encephalitis. He was treated with oxcarbazepine for suspected focal seizures and later received high-dose IV methylprednisolone followed by a prolonged prednisone taper.<br /><br />The key message is that early recognition of probable AE, even when antibodies are negative, is critical because timely treatment may improve recovery and reduce relapse and cognitive impairment.

Asset Subtitle

Alicia H. Darwin

Meta Tag

Author List Alicia H. Darwin, Tiana Dodd

Category Clinical Vignettes

Concept Autoimmune Encephalitis

Concept Subacute Neurocognitive Symptoms

Concept Antibody-Negative Autoimmune Encephalitis

Concept Graus Diagnostic Criteria

Concept Psychiatric Symptoms

Distinguished Non-Finalist

Presenter Organization University of South Florida Morsani College of Medicine

Presenting Author Alicia H. Darwin

Track Adult

Keywords

autoimmune encephalitis

antibody-negative

limbic encephalitis

temporal lobe

subacute confusion

memory impairment

MRI mesial temporal lobe

CSF lymphocytic pleocytosis

EEG slowing

high-dose corticosteroids

Autoimmune Encephalitis

Subacute Neurocognitive Symptoms

Antibody-Negative Autoimmune Encephalitis

Graus Diagnostic Criteria

Psychiatric Symptoms