Encephalitis. Identifying the specific cause is key to effective management.

Acute viral encephalitis and postinfectious encephalomyelitis affect both children and adults. Enteroviruses, HSV types 1 and 2, and arboviruses are the most common causes of encephalitis in the United States; however, the differential diagnosis is broad. History taking and physical examination can provide clues to the cause, but the diagnosis is usually established on the basis of CSF analysis, viral culture, MRI, and serologic testing, when indicated. In the future, PCR techniques may enhance rapidity of diagnosis. Until the specific cause is identified, empirical therapy should be given. Because complications can be severe, all patients with encephalitis should be monitored in a facility capable of providing supportive intensive care. Long-term follow-up is important to detect sequelae, particularly in patients with eastern equine or HSV encephalitis.