Accurately and promptly diagnosing suspected cases of encephalitis is essential. Two main tests are used to diagnose encephalitis. They are:
- brain scans – such as computerised tomography (CT) scans and magnetic resonance imaging (MRI) scans
- lumbar punctures
These procedures are briefly described below.
Brain scans
CT scans or MRI scans 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 swelling in the wall of an artery).
However, in the early stages of encephalitis, brain scans do not always rule out a diagnosis. This is because the swelling inside the brain that can be detected with a brain scan often only occurs as the symptoms of encephalitis progress to a more advanced stage.
See the Health A-Z topics about CT scan and MRI scan for more information about these procedures.
Lumbar puncture
A lumbar puncture, also known as a spinal tap, is a procedure that is used to test a sample of spinal cord fluid. The fluid, called cerebrospinal fluid (CSF), surrounds your brain and spinal cord and supports and protects them.
A lumbar puncture is performed by inserting a hollow needle into the lower part of your spinal canal so that a sample of CSF can be drawn out. The fluid is subjected to a series of tests, which can help to confirm a diagnosis of encephalitis, such as checking it for the presence of infection.
See the Health A-Z topic about lumbar puncture for more information about the procedure.
Other tests
Other tests that are occasionally used to help confirm or rule out a diagnosis of encephalitis include the laboratory screening of blood, urine and other body fluids. Screening these substances can help to detect and identify infections of the brain or spinal cord. Results from these tests can also help to exclude other conditions that mimic encephalitis.
