It may take a number of tests to diagnose herpes encephalitis.
Polymerase Chain Reaction (PCR). The polymerase chain reaction (PCR) assay of cerebrospinal fluid detects tiny amounts of DNA from the virus, and then replicates them millions of times until the virus is detectable. This test can identify specific strains of the virus. PCR identifies HSV in cerebrospinal fluid and gives a rapid diagnosis of herpes encephalitis in most cases, eliminating the need for biopsies. The CDC recommends PCR for diagnosing herpes central nervous system infections.
Imaging Tests. Magnetic resonance imaging (MRI) scans may be used to differentiate encephalitis from other conditions.
Brain Biopsy. Brain biopsy is the most reliable method of diagnosing herpes encephalitis, but it is also the most invasive and is generally performed only if the diagnosis is uncertain. With the increased use of PCR, biopsies for herpes are now only rarely performed.
Canker Sores (Aphthous Ulcers). Simple canker sores (known medically as aphthous ulcers) are often confused with the cold sores of herpes simplex virus 1 (HSV-1). Canker sores frequently crop up singly or in groups on the inside of the mouth or on or under the tongue. Their cause is unknown, and they are common in perfectly healthy people. They are usually white or grayish crater-like ulcers with a sharp edge and a red rim. They usually heal in 2 weeks without treatment.
Thrush (Candidiasis). Candidiasis is a yeast infection that causes a whitish overgrowth in the mouth. It is most common in infants but can appear in people of all ages, particularly people taking antibiotics or those with impaired immune systems.
|Click the icon to see an image of thrush.|
Other conditions that may be confused with oral herpes include herpangina (a form of the Coxsackie A virus), sore throat caused by strep or other bacteria, and infectious mononucleosis.
Review Date: 11/05/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.