DIAGNOSTIC CHALLENGES OF SERONEGATIVE AUTOIMMUNE ENCEPHALITIS

Document Type

Conference Proceeding

Publication Date

6-17-2022

Publication Title

Journal of General Internal Medicine

Abstract

CASE: A 77-year-old male with a history of HTN and hypothyroidism presented to the ED with acute altered mental status (AMS) after a reported episode of seizure-like activity. Prior to the episode, the patient was in his normal state of health with normal mental status. Initial physical exam revealed that the patient was oriented only to name with normal vitals. Initial work up with CT head, CTA, CXR, EEG and urine toxicology was unremarkable, CVA was ruled out with a NIHSS of 1, and no electrolyte or other lab irregularities were noted. On admission, further work up was significant for elevated free T4 levels to 3.34 and significantly low TSH levels of <0.01 despite the patient's hypothyroid history, prompting treatment with methimazole and a euthyroid state was achieved. However, the patient continued to experience an altered mental status of ANO x 0-1. Further neurological investigation revealed an unremarkable MRI brain, continuous EEG notable for diffuse background slowing with no seizure activity, and LP revealed CSF studies notable for lymphocytic pleocytosis with WBC of 27, 94% lymphocytes, elevated protein of 345.4, and a glucose of 62, with infectious CSF panel negative for VZV, HSV, EBV, West Nile Virus, and CMV. Autoimmune studies were positive for ANA, dsDNA antibodies, antihistone antibodies, and elevated rheumatoid factor of 33, while paraneoplastic panel, SSA antibody, SSB antibody, and thyroglobulin antibody were negative. A diagnosis of seronegative autoimmune encephalitis was suspected, and after 17 days of AMS the patient was initiated on empiric steroid therapy with a 5-day treatment course of 1g IV methylprednisolone. After 2 days of steroid treatment, the patient demonstrated significant signs of improvement and rapidly recovered his baseline mental status. IMPACT/DISCUSSION: Autoimmune encephalitis (AE) is a rare, immune mediated syndrome causing inflammation of the brain that typically manifests with acute or subacute characteristic presentations of seizures, cognitive impairment, and neuropsychiatric symptoms. Seronegative AE is a disease subtype that has a suspected autoimmune etiology without an identifiable autoantibody in the serum or CSF, which can create diagnostic challenges. Despite the recent discovery of new neuronal autoantibodies, many remain unidentified at present, thus a negative serology panel should not delay treatment in cases of suspected AE. Patients with a strong clinical suspicion of this disease process should be treated empirically with first line immunotherapy with 1g IV methylprednisolone for 3-5 days. Second line treatment includes IVIG or plasmapheresis, followed by third line treatment with rituximab. CONCLUSION: Autoimmune encephalitis is a diagnosis that should be strongly considered in patients with an unexplained spectrum of neuropsychiatric symptoms that do not correspond to vascular, infectious, toxic, or metabolic causes. Strong clinical suspicion should prompt treatment with empiric steroids without delay.

Volume

37

Issue

Suppl 2

First Page

S444

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