Encephalitis is inflammation of the brain tissue, most often from viruses such as herpes simplex or from autoimmune causes. It is an emergency, and acyclovir should start as soon as the diagnosis is suspected.
Key symptoms
- Fever and headache
- Confusion, or personality and behavior change
- Seizures
- Drowsiness progressing to coma
- Speech problems, weakness or memory loss
What you find on exam
- Glasgow Coma Scale and mental status
- Focal neurologic deficits
- Neck stiffness (suggests meningoencephalitis)
- Skin rash, vesicles or tick bites
- Vital signs for sepsis
Tests
- Lumbar puncture: lymphocytes, normal glucose, raised protein, HSV PCR
- Brain MRI: temporal lobe changes in HSV
- EEG for seizures or nonconvulsive status
- Autoimmune antibodies (such as anti-NMDA receptor) if viral tests are negative
Treatment basics
- Empiric IV acyclovir right away
- Add antibiotics for meningitis until bacterial causes are ruled out
- Seizure control with levetiracetam or another antiseizure drug
- ICU care for airway and raised intracranial pressure
- Autoimmune causes: steroids, IV immunoglobulin or plasma exchange
Red flags
- Seizures or status epilepticus
- Falling level of consciousness
- Delay in starting acyclovir
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.