Determining an infectious or autoimmune etiology in encephalitis

Area of Science:

• Neurology
• Infectious Diseases
• Immunology

Background:

• Acute infectious encephalitis (IE) and autoimmune encephalitis (AE) share similar early symptoms and diagnostic workups.
• Differentiating between IE and AE is crucial for timely and appropriate treatment.

Purpose of the Study:

• To identify routine laboratory markers present at initial patient evaluation that can distinguish between IE and AE.
• To aid in the early risk stratification of patients with acute meningoencephalitis.

Main Methods:

• A multi-center retrospective study was conducted involving 333 patients with confirmed acute meningoencephalitis.
• Demographic and clinical data, including laboratory markers, were analyzed from patients diagnosed with definitive IE (pathogen identified) or AE (autoantibody identified).

Main Results:

• Non-bacterial IE (NB IE) was identified in 45.4%, bacterial IE in 28.5%, and AE in 26.1% of patients.
• NB IE cases showed higher frequencies of fever, elevated cerebrospinal fluid (CSF) white blood cell (WBC) counts and protein levels, and lower CSF glucose compared to AE.
• Specific criteria (fever, CSF WBC ≥50 cells/μL, CSF protein ≥75 mg/dL) were associated with a low likelihood of AE (95% negative predictive value).

Conclusions:

• Specific laboratory findings at presentation can help differentiate between infectious and autoimmune encephalitis.
• The presence of fever, elevated CSF WBC, and elevated CSF protein may suggest IE and help rule out AE.
• These findings support the use of routine laboratory markers for early risk stratification in acute meningoencephalitis.