- Infection of brain parenchyma of the temporal lobes and inferior frontal lobe causing distinct neurologic abnormality
- Gray matter is predominantly affected (cognitive / psychiatric signs, lethargy, seizure)
- New psychiatric symptoms (HSV)
- Cognitive deficits
- Aphasia, amnesia, confusion
- Movement disorder (arboviruses)
- Fever and meningeal signs are almost always present
- Dysuria and pyuria (St. Louis encephalitis)
- Extreme lethargy (West Nile encephalitis)
Altered mental status and fever
- Imaging identifies abnormalities in medial temporal and inferior frontal gray matter in HSV
- Bloody tap consistent with HSV
Often it is unclear which type of encephalitis is present and starting Acyclovir empirically is appropriate. In addition to the pathogens below, possible causes can include West Nile Virus, EBV, HIV, toxoplasmosis, or rabies.
- Acyclovir 10mg/kg (10-15mg/kg for pediatrics) every 8hrs
- Acyclovir 10mg/kg every 8hr
Tick Associated (Borrelia burgdorferi, Ehrlichiosis or Rickettsia)
- Doxycycline 200 mg IV once followed by 100 mg IV twice daily
Admit in all cases
- Somand D, Meurer W. Central Nervous System Infections. EMCNA 2009; 27: 89-100.
- Loring KE, Tintinalli JE: Central Nervous System and Spinal Infections, in Tintinalli JE, Kelen GD, Stapczynski JS (eds): Emergency Medicine, A Comprehensive Study Guide, ed 7. New York, McGraw-Hill, 2011, (Ch) 168:p 1175-1176.
- Howes DS et al. Encephalitis Workup. Oct 12, 2015. http://emedicine.medscape.com/article/791896-workup#showall