Doctors use the term encephalitis to refer to inflammation of the brain, usually caused by bacterial, fungal or viral infections. In the 2008 edition of "Harrison's Principles of Internal Medicine," University of Washington Professor Lawrence Corey, M.D. reports that herpes simplex accounts for 10 to 20 percent of encephalitis cases in the United States---for an estimated total of 2.3 million cases per year. According to Dr. Corey, most cases occur in people between the ages of 5 and 30 or people over 50.
Types
According to the National Institute of Neurological Disorders and Stroke (NINDS), herpes simplex encephalitis can be primary or secondary. Doctors use the terms "primary encephalitis" or "acute viral encephalitis" to describe encephalitis that develops around the same time or shortly after the classic, painful mouth or genital blisters of herpes simplex. Secondary encephalitis, also known as "post-infective encephalitis," develops after other symptoms have resolved.
Symptoms
Early clinical features of herpes simplex encephalitis include mild flu-like illness with headache, fever, poor appetite and drowsiness. After about five days, according to NINDS, symptoms typically get worse. According to Dr. Corey, herpes simplex typically targets the brain's temporal lobe, which regulates emotional, sexual and eating behaviors. Therefore, impaired judgement, personality changes, and abnormal behavior may be the first neurological symptoms to present. As the infection spreads to other areas of the brain, mental confusion, hallucinations, partial paralysis, memory loss or problems with speech, hearing or vision may appear.
Time Frame
Primary encephalitis symptoms develop around the same time as other symptoms of herpes simplex, while secondary encephalitis symptoms usually appear two to three weeks after other symptoms have subsided. According to Dr. Corey, about 30 percent of cases develop during the first outbreak of herpes simplex. The remaining 70 percent develop during recurrent outbreaks or as secondary encephalitis in people who exhibit no other symptoms of active herpes simplex. Each episode of encephalitis usually lasts about two weeks. Some people, especially children, experience more than one.
Treatment
Treatment for herpes simplex encephalitis begins with intravenous acyclovir. Some doctors, according to University of Michigan infectious disease specialist Dr. Cecilia Big in the Dec. 2009 edition of "Clinical Medicine and Research," prescribe steroids to reduce inflammation and diuretics, such as mannitol, to control excess swelling in the brain. Additional treatment is symptom-based. For example, sedatives are used to control abnormal behavior and anticonvulsants are used to control seizures.
Complications
According to the University of Maryland Medical Center, approximately 30 percent of patients treated for herpes simplex virus encephalitis die. That figure rises to about 70 percent in untreated patients. According to Dr. Big, 50 percent of survivors experience permanent, severe disability. Specific symptoms correlate with the location of the infection. Patients with significant temporal lobe involvement, for example, may exhibit permanent deficits in impulse control and judgement, especially involving eating or sexual behavior. Patients with extensive frontal lobe involvement may lose cognitive function and even become demented.
References
- "Harrison's Principles of Internal Medicine, 23rd Edition"; Anthony S. Fauci, M.D. et al.; 2008
- National Institute of Neurological Disorders and Stroke: Meningitis and Encephalitis Fact Sheet
- "Clinical Medicine and Research"; Viral Infections of the Centeral Nervous System; Cecilia Big, M.D. et al.; Dec. 2009
- University of Maryland Medical Center: Viral Encephalitis
- MayoClinic.com: Encephalitis: Treatments and Drugs
