Tests are needed to separate encephalitis from other brain conditions so that the appropriate treatment can be started as soon as possible.


Brain scans (CT, MRI) can be used to highlight the extent of brain inflammation and help to distinguish encephalitis from other conditions, such as stroke, brain tumours and aneurysms.


A  Lumbar puncture, also known as a spinal tap, is used to test a sample of cerebral spinal fluid (CSF). This fluid is produced by the brain and drains into the spinal cord.  The contents of this fluid can indicate infection and inflammation in the brain.  In some cases, samples of CSF can be tested to identify the virus or other infectious agent.  (Note, this procedure is not performed is the pressure within the brain is too high).


An Electroencephalogram (EEG) is used to monitor brain activity. People who are ill with encephalitis may have abnormal brain activity.


Blood, urine and other body fluids can be tested for viruses or other infectious agents and to determine the presence of antibodies and foreign proteins.  Such tests can also rule out metabolic conditions (such as liver disease) that have similar symptoms.


Note: the exact cause of encephalitis is not always found. In some people, encephalitis is diagnosed when other causes for their symptoms have been excluded after tests.

This information is taken from the Book “Understanding Encephalitis” by Elaine Dowell.  The book is available from Amazon Understanding Encephalitis.



Links are to a pdf if the article is free and to the Pubmed page is the article is not free

Consensus guidelines for the investigation and management of encephalitis in adults and children in Australia and New Zealand.  Abstract- Encephalitis is a complex neurological syndrome caused by inflammation of the brain parenchyma. The management of encephalitis is challenging because: the differential diagnosis of encephalopathy is broad; there is often rapid disease progression; it often requires intensive supportive management; and there are many aetiologic agents for which there is no definitive treatment. Patients with possible meningoencephalitis are often encountered in the emergency care environment where clinicians must consider differential diagnoses, perform appropriate investigations and initiate empiric antimicrobials. For patients who require admission to hospital and in whom encephalitis is likely, a staged approach to investigation and management is preferred with the potential involvement of multiple medical specialties. Key considerations in the investigation and management of patients with encephalitis addressed in this guideline include: Which first-line investigations should be performed?; Which aetiologies should be considered possible based on clinical features, risk factors and radiological features?; What tests should be arranged in order to diagnose the common causes of encephalitis?; When to consider empiric antimicrobials and immune modulatory therapies?; and What is the role of brain biopsy?