Encephalitis resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Moises Romo M.D.

Synonyms and Keywords: encephalitis management, encephalitis workup, encephalitis approach,encephalitis management, encephalitis treatment, encephalitis diagnosis

Overview

Encephalitis refers to the inflammation of the brain. The causes of encephalitis are mostly infectious, beign viruses, bacteria, fungi, or parasites the possible agents. Presentation usually involves headache, fever, confusion, neck stiffness (Kernig and Brudzinski signs), and vomiting. Diagnosis is typically based on clinical presentation and supported by blood tests, medical imaging, and analysis of cerebrospinal fluid. A rapid identification of encephalitis is crucial to reduce sequelae. Management is directed against the affecting agent (antivirals, antibiotics), reducing swelling, and supportive measures.

Causes

Life Threatening Causes

Life-threatening causes include conditions that may result in death or permanent disability within 24 hours if left untreated.

• All causes of encephalitis may be potentially fatal or disabiling if left untreated in 24 hours.; among them:
  • Infectious
    • Bacterial
      • Tuberculosis
      • Treponema pallidum
      • Mycoplasma
    • Viral
      • Herpes simplex
      • Epstein-Barr virus
      • Zoster
      • Rabies
      • HIV
      • Cytomegalovirus
      • West Nile virus
      • St. Louis encephalitis virus
      • Japanese encephalitis virus
    • Fungal
      • Coccidioidomycosis
      • Blastomycosis
      • Histoplasmosis
      • Cryptococcosis
    • Protozoan
      • Granulomatous amebic
      • Toxoplasma
      • Bartonella Henselae
  • Autoimmune
  • Encephalitis lethargica
  • Limbic encephalitis

Diagnosis

Shown below is an algorithm summarizing the diagnosis of encephalitis according to the American Academy of Neurology guidelines:

Patient meets criteria for encephalitis

Perform:• CSF analysis (at least 20 ml): Opening pressure, WBC count with differential, RBC count, protein, glucose Gram stain and bacterial culture • Routine blood cultures • HSV-1/2 PCR • VZV PCR • Enterovirus PCR • Cryptococcal antigen and/or India Ink staining • Oligoclonal bands and IgG index • VDRL • HIV serology • Hold acute serum and collect convalescent serum 10–14 d later for paired antibody testing • Neuroimaging (MRI preferred to CT, if available) • Chest imaging (Chest x-ray and/or CT) • EEG

Diagnostic Criteria for Encephalitis and Encephalopathy of Presumed Infectious or Autoimmune Etiology according to the International Encephalitis Consortium

Major Criterion (required):

Patients presenting to medical attention with altered mental status (defined as decreased or altered level of consciousness, lethargy orpersonality change) lasting ≥24 h with no alternative cause identified.

Minor Criteria (2 required for possible encephalitis; ≥3 required for probable or confirmeda encephalitis):

Documented fever ≥38° C (100.4°F) within the 72 h before or after presentationb

Generalized or partial seizures not fully attributable to a preexisting seizure disorderc

New onset of focal neurologic findings

CSF WBC count ≥5/cubic mmd

Abnormality of brain parenchyma on neuroimaging suggestive of encephalitis that is either new from prior studies or appears acute in onsete

Abnormality on electroencephalography that is consistent with encephalitis and not attributable to another cause.f

Do not modify

Treatment

Shown below is an algorithm summarizing treatment of encephalitis according to the American Academy of Neurology guidelines: