HSV | Common cause of encephalitis. Predilection for temporal lobes, sylvian fissure, orbital–frontal cortex. Associated with periodic lateralizing epileptiform disharges on EEG, vesicles on the skin, focal seizures, hemiparesis, aphasia, and cranial neuropathies. |
HHV-6 | Rarely causes encephalitis. |
| Typically occurs in infants and small children, and has a focal onset. |
VZV | Uncommon cause of encephalitis. |
| Typically occurs in children. Usually associated with vesicular rash, headache, vomiting, altered mental status, and seizures. Can also cause ischemic or hemorrhagic infarcts. |
EBV | Rarely causes encephalitis. |
| Often associated with rash or mononucleosis. |
CMV | Rarely causes encephalitis. |
| More common in immunocompromised patients. |
EV | Common cause of CNS infection, but rarely causes encephalitis. |
| Often associated with pharyngitis, gastroenteritis, and rash. |
Arboviruses | Most common causes of worldwide encephalitis. |
WNV | Associated with headache, vomiting, diarrhea, abdominal pain, and rash. Presents with seizures, flaccid paralysis, and cranial neuropathies. |
EEE | Rare cause of encephalitis, but children are most affected. |
| Presents with sudden high fever, seizures, and altered mental status. |
SLE | Rarely causes encephalitis. Presents with headache. |
La Crosse | Rare cause of encephalitis, but occurs most commonly in children. |
| Associated with upper respiratory illness, abdominal pain, and seizures. |
Influenza | Rarely causes encephalitis in the United States. |
| Presents with a prodrome of myalgias and fever, progresses to cause seizure. |
Rabies | Rare in developed countries, but common throughout the world. |
Encephalitic | Presents with anxiety, hydrophobia, aerophobia, hypersalivation, and seizures. |
Paralytic | Presents with progressive peripheral nerve paralysis. |
Measles | Rarely causes encephalitis, more commonly causes SSPE. |
| SSPE occurs months to years after measles infection and presents with progressive dementia, myoclonus, seizures, and ataxia. |
Mumps | Rarely causes encephalitis. |
| Presents with fever, headache, and a typically mild course. |
| Postinfectious encephalomyelitis: occurs 7–10 d after mumps infection and is more severe. Symptoms include seizure, hemiparesis, and altered mental status. |