Herpesviral encephalitis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 6, 2016
StartDiseasesHerpesviral encephalitis

Herpesviral encephalitis, or herpes simplex encephalitis is a rare disease that occurs when the herpes simplex virus causes inflammation in the brain (encephalitis). It is sometimes a complication of another disease.


Definition & Facts

Herpes simplex encephalitis must be considered a medical emergency, for it is fatal if it is left untreated. Even if it is treated, some patients suffer neurological problems after the disease has run its course. These problems can be temporary or permanent, and the virus remains in the body, though in a dormant state, even if the patient recovers.

Studies have shown that the incidence of herpes simplex encephalitis is about 1 in 500,000. The disease strikes about 5.9 babies per 100,000 births.

Half of the adults who get herpesviral encephalitis are over 50 years old, and people over 55 as well as infants tend to have the worst outcomes. How well they recover from the disease depends on the health of their immune system, whether they already had a neurological disorder before they caught the disease and how severe the viral infection is.

Symptoms & Complaints

The symptoms of herpesviral encephalitis can take a few days to develop or can strike without warning. The early symptoms of the disease are fever, headaches, vomiting, and seizures. Other symptoms are mental confusion, disorientation, weakness, and sleepiness.

Some patients have a stiff neck and a stiff back, abnormal speech patterns, and paralysis if the meninges, the protective membranes that cover the brain, are affected.

After the initial symptoms, the person starts to have trouble communicating. They cannot speak or write in ways that are intelligible to others. They develop problems with their memory, lose their sense of smell, and become sensitive to light.

Personality changes are also common. The patient may be hyperactive or psychotic, which means they sense or believe things that are not real. They may become partially paralyzed, lose consciousness or sink into a coma.

In some cases, the virus attacks the retina of the eye and causes retinitis, a condition that can lead to blindness.

The brain damage that can be a complication of herpesviral encephalitis can be minimal or devastating. The damage can affect one part of the brain, like the area responsible for muscle control or affect several parts of the brain. It can be diffuse, which means the damage is spread throughout the brain.


The cause of herpesviral encephalitis is most often herpes simplex virus type I, though in rare cases the cause is herpes simplex virus type II. The latter is more likely to affect newborn babies, who receive the virus as they pass through their mother’s vagina. Adults get the virus through sexual contact, contact with virus-shedding lesions or if the virus enters a tiny break in the skin.

A herpes simplex outbreak presents as tiny, fluid-filled blisters on the patient’s genitals (genital herpes) or lips (cold sores). These blisters are rarely present when the patient contracts encephalitis. Herpesviral encephalitis can occur when the dormant virus from a previous infection becomes active.

Diagnosis & Tests

Diagnosis of herpesviral encephalitis begins with the health care provider observing the patient’s symptoms and taking their medical history. The doctor then does a neurological examination to evaluate the patient’s sensory function and motor functions. Through this exam, the doctor sees how well the patient can walk and coordinate their arms and legs and how well they balance. The doctor also observes the patient’s moods and behavior.

The doctor may give the patient a lumbar puncture (spinal tap) to check their cerebrospinal fluid. This tests consists of a needle inserted between the vertebrae in the patient’s lower back. The cerebrospinal fluid is subjected to a polymerase chain reaction (PCR) assay, which can find extremely small amounts of the virus’s DNA and replicates them until the virus is identifiable. 

Blood tests can find antibodies that specifically fight either the herpes simplex I or herpes simplex II virus. Other types of tests search for glycoproteins found on the virus. Other tests used to diagnose a herpes virus infection include the Western Blot test.

Magnetic resonance imaging (MRI)'s and computed tomography (CT) scans are utilized to examine the structures of the patient’s brain. They show the type and extent of the inflammation in the brain caused by herpesviral encephalitis. The ways that the herpes virus damages the brain tissue are specific and are best seen through these imaging technologies. An electroencephalogram monitors the patient’s brain waves through electrodes attached to their skull.

In rare cases, the doctor orders a brain biopsy where tiny bits of brain tissue are extracted and studied under an electron microscope for the presence of the virus. This test is done only if the doctor isn’t sure of the diagnosis.

Treatment & Therapy

Fortunately, encephalitis caused by the herpes virus can be treated while many other causes of encephalitis cannot be. Patients with herpesviral encephalitis are treated with the antiviral drug, acyclovir. They are treated in the hospital, and the drug is delivered intravenously for up to 14 days for adults. Babies may also need to be on the drug for weeks. 

Treatment must begin as soon as the doctor suspects that the patient is suffering from herpesviral encephalitis. The doctor may also prescribe anti-seizure drugs such as lorazepam and corticosteroids to reduce the swelling in the brain.

Sedatives ease the patient’s restlessness, and painkillers such as ibuprofen are given to patients suffering from mild symptoms. The patient should start to get better after about a day and be fully recovered after about a month if there are no side effects.

Prevention & Prophylaxis

The best way to avoid herpesviral encephalitis is to practice safe sex and to subject oneself and one's sexual partners to regular STD screening. A person should also avoid kissing someone with a cold sore and use a latex condom during sexual activity.

If a pregnant woman has an outbreak of genital herpes blisters, she may opt for a caesarean section to lower the risk of her baby contracting herpes and developing herpesviral encephalitis.