History |
Symptoms – Fever, decreased level of consciousness, irritability or personality/behavior change, seizures, focal neurologic abnormalities |
Travel |
Exposure (animals, insects, freshwater swimming, toxins) |
Immunizations and immune status |
Physical findings |
Vital signs and general examination |
Neurologic examination, particularly for GCS and focal findings |
Laboratory studies |
Blood tests:
|
Urine tests:
|
CSF studies (perform lumbar puncture after neuroimaging if a mass lesion has not been ruled out):
|
Other laboratory tests to consider:
|
Ancillary studies |
Neuroimaging – MRI preferred, but perform CT if MRI not promptly available, impractical, or cannot be performed |
EEG – As soon as is feasible |
Presumptive diagnosis |
Based upon ALL of the following:
|
Treatment |
Stabilization |
Support airway, breathing, and circulation |
Endotracheal intubation for GCS ≤8 or compromised airway |
Fluid resuscitation with normal saline (20 mL/kg, initial bolus) for signs of hypovolemia or shock |
Treat seizures with lorazepam (0.1 mg/kg IV) |
Empiric antimicrobial therapy |
Empiric acyclovirΔ (for all patients with suspected acute infectious encephalitis):
|
Empiric antibiotics (give until bacterial meningitis has been excluded):
|
Consider empiric treatment for other causes (eg, Mycoplasma pneumoniae, influenza, Rocky Mountain spotted fever, cat scratch disease, Q fever, ehrlichiosis) as indicated based upon clinical findings, season, exposure history, and other risk factors§ |
BUN: blood urea nitrogen; CBC: complete blood count; CMV: cytomegalovirus; CNS: central nervous system; CSF: cerebrospinal fluid; CT: computed tomography; EBV: Epstein-Barr virus; EEG: electroencephalography; GCS: Glasgow coma scale; HHV-6: human herpesvirus 6; HIV: human immunodeficiency virus; HSV: herpes simplex virus; IV: intravenous; LFT: liver function test; NMDAR: anti-N-methyl-D-aspartate receptor; MRI: magnetic resonance imaging; PCR: polymerase chain reaction; VZV: varicella zoster virus; VGKC: voltage-gated potassium channel; WNV: West Nile virus.
* PCR testing may consist of multiplex testing for multiple viral and bacterial pathogens simultaneously in a single CSF sample (eg, FilmArray meningitis/encephalitis panel [BioFire]) or individual PCR tests for specific pathogens. Testing for HSV, enterovirus, and parechovirus should be performed in all patients; testing for additional pathogens may be warranted based upon history and epidemiology (eg, Mycoplasma pneumoniae, influenza, CMV, EBV, HHV-6, VZV, WNV).
¶ Refer to separate UpToDate topics for details regarding the approach to diagnostic testing in children with suspected toxic metabolic encephalopathy, inborn errors of metabolism, or autoimmune encephalitis.
Δ Empiric acyclovir therapy is provided to all patients with suspected encephalitis until HSV infection has been excluded (ie, by negative CSF PCR). Refer to UpToDate topics on HSV for additional details.
◊ The doses of acyclovir and vancomycin listed in this table are for patients with normal kidney function. Dosing adjustment is required in patients with renal insufficiency. Refer to drug monographs for details.
§ Empiric therapy for M. pneumoniae typically consists of a macrolide antibiotic (eg, azithromycin). Several agents are available for treatment of influenza in children (oseltamivir, peramivir, baloxavir, and zanamivir); refer to UpToDate's topics on seasonal influenza in children for details. Empiric therapy for cat scratch disease, Rocky Mountain spotted fever, Q fever, or ehrlichiosis typically consists of doxycycline (rifampin is added in the case of cat scratch disease). Risk factors for these infections include exposure to or bites/scratches from cats or kittens (cat scratch disease), exposure to ticks in endemic regions (Rocky Mountain spotted fever and ehrlichiosis) and exposure to farm animals (Q fever). Refer to separate UpToDate content on these infections for additional details.
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