Last updated: Tuesday, 30, November, 2010
CausesAppropriate Tests

Cerebrospinal fluid examination, diagnostic imaging and electroencephalography to support clinical diagnosis.

Herpes simplex virus is the most common cause of sporadic disease; in the absence of conflicting evidence, appropriate therapy should be instituted.

In otherwise undiagnosed, severe, progressive encephalitis, brain biopsy may be required as a last resort.

See also Meningitis

Viral infection

Consideration of seasonal and geographic factors, recent travel, age, and sexual activity may assist in defining the likely viral agent.

If appropriate: throat/nasopharyngeal swabs, CSF, faeces - virus detection, culture.

If there is a past history of exposure to sick horses or bats, equine morbillivirus antibodies serology or bat lyssavirus antibodies (rabies virus antibodies) may be indicated.

Herpes simplex infection

Arbovirus infections, especially

  • Murray Valley encephalitis
Arbovirus antibodies.

Enterovirus infections, especially

  • Coxsackieviruses
  • Echoviruses
Enterovirus antibodies.

Infectious mononucleosis

HIV infection

See HIV infection, AIDS

Measles, including

  • Acute infection
  • SSPE


Serum, CSF - measles virus antibodies; CSF immunoglobulin studies (oligoclonal bands).

Rubella is a rare cause: rubella antibodies should be requested if measles antibodies negative.


Varicella zoster infection


Progressive multifocal leucoencephalopathy

A rare demyelinating disorder affecting immunosuppressed patients, due to JC virus (a polyomavirus).

Mycoplasma infection