Clinical presentation and diagnosis of encephalitis
Viral encephalitis is a serious central nervous system (CNS) infection. It is difficult to differentiate from viral and bacterial meningitis. Encephalitis usually presents with an acute change in mental status – this can be subtle, or associated with confusion or coma. Meningitis typically presents with an acute history of fever, neck stiffness and altered conscious state. Headache, photophobia, and nausea or vomiting are often prominent.
Suspect encephalitis in patients with acute fever and focal neurological symptoms and signs, including seizures, behavioural changes, focal neurological deficits and coma.
Diagnostic tests for encephalitis should include analysis of cerebrospinal fluid (CSF), serum, respiratory samples and faecal samples, as well as magnetic resonance imaging (MRI) and electroencephalogram (EEG). A mild CSF pleocytosis is usually present, which can make it difficult to distinguish encephalitis from bacterial or viral meningitis. Seek expert advice, particularly for patients with immune compromise, returned travellers and those with unusual epidemiological exposures.
See the Consensus guidelines for the investigation and management of encephalitis in adults and children in Australian and New Zealand for detailed information.
For initial antimicrobial therapy, see Empirical therapy for encephalitis.