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Herpes Meningoencephalitis

What is herpes meningioencephalitis?

The meninges are the layers of thin tissue that cover your brain. If these tissues become infected, it’s called meningitis. When your brain becomes inflamed or infected, the problem is called encephalitis. If both the meninges and the brain are involved, the condition is called meningoencephalitis.

Encephalitis involving herpes is a medical emergency. It needs to be promptly diagnosed and treated. This disease is fatal in a third or more of cases when it is not treated. Many people who survive it have long-term problems afterward.

What causes herpes meningioencephalitis?

Meningitis and encephalitis may be caused by bacteria, fungi, or other types of germs. But many are caused by viruses, and many kinds of viruses can be to blame.

About 1 in 10 cases of encephalitis is caused by the herpes simplex virus. Most are caused by herpes simplex virus type 1 (HSV1), the virus that also causes cold sores. The disease may also be caused by herpes virus type 2 (HSV2). This virus can be spread by sexual contact or from an infected mother to her baby during childbirth. HSV1 infection can also be sexually transmitted to the genital area. These viruses remain in the body throughout a person's life, even when they're not causing signs of infection.

Sometimes the meningoencephalitis occurs during the initial infection with the herpes simplex virus, but most often it is caused by reactivation of the virus from an earlier infection.

What are the symptoms of herpes meningoencephalitis?

If you have viral meningitis, symptoms may include fever, light sensitivity, headache, and a stiff neck. If you have other symptoms, such as confusion, seizures, sleepiness, or a focal neurologic deficit—a nerve function problem that affects a specific area — these may suggest that your brain is also affected, and your doctor may diagnose it as meningoencephalitis.

These are possible symptoms of meningoencephalitis:

  • Headache
  • Fever
  • Neck stiffness
  • Sensitivity to light
  • Seizures
  • Trouble thinking clearly
  • Personality changes
  • Unusual behaviors
  • Unconsciousness

How is herpes meningoencephalitis diagnosed?

If, after reviewing your medical history and symptoms, your doctor thinks you may have herpes meningoencephalitis, he or she will order various tests and exams to confirm the diagnosis. Other tests may include:

  • Neurological exam. Your doctor will do a neurological exam to look for changes in motor and sensory function, vision, coordination and balance, mental status, and in mood or behavior.
  • Lumbar puncture. In this procedure, your doctor will take a sample of spinal fluid. Cells and other substances in this fluid may give your doctor important clues.


  • Imaging. Your doctor may want to create images of your brain using a CT or MRI scan.
  • EEG. An EEG measures brain waves by placing electrodes onto your scalp.
  • Bloodtests. Testing the blood helps identify infection..

If doctors think that a newborn has herpes encephalitis resulting from infection with HSV2 while passing through the birth canal, they may check samples of the baby's blood and spinal fluid.

How is herpes meningoencephalitis treated?

Treating the cause of your infection is the primary treatment. Since most cases of meningoencephalitis are caused by the herpes virus, the antiviral acyclovir is used to treat it. You may need to take this medicine through an intravenous (IV) line for 10 to 14 days. Doctors may also give you medicine to reduce swelling in the brain and to treat or prevent seizures.

Doctors may treat babies with this disease with acyclovir for several weeks.

Depending on the severity of your infection, you may need to be treated in the hospital.

What are the complications of herpes meningoencephalitis?

With treatment, most people with this disease start to improve within a day or two and tend to recover fully within about a month. But without treatment, very serious complications can set in, including death.

Even with treatment, some people with severe cases may have long-term brain damage. They may have trouble thinking, controlling their body, and hearing, seeing, or speaking. They may need to take medicines for a long time, and they may require long-term care.

Can herpes meningoencephalitis be prevented?

Avoiding herpes virus infections in the first place can help you prevent herpes meningoencephalitis. Ways to avoid infections from herpes viruses include:

  • Abstain from sex or have only one sex partner who has been tested for the virus and isn't infected.
  • Use a latex condom, which can reduce — but not entirely prevent — the risk of infection.
  • Avoid kissing people with cold sore blisters. It's important to keep in mind that most people have already been infected with HSV1 virus by the time they're 20 years old. If you've already been infected, the virus goes dormant inside your body except during outbreaks. 

Some pregnant women who have had genital herpes outbreaks may want to have their babies delivered by cesarean section. This may prevent meningoencephalitis in newborns.

When should I call my health care provider?

Treating herpes meningoencephalitis as soon as possible is essential. If you’re feeling neck stiffness, having any neurological problems (including seizures, changes in consciousness, or feeling sleepy), are sensitive to light, or are running a fever along with a bad headache, call your doctor and have the problem treated promptly.

If you have already been diagnosed with herpes meningoencephalitis and are being treated, it's very important to let your doctor or nurse know if any of your symptoms get worse or if you develop any new symptoms, as these could be signs that the infection is getting worse despite treatment.

Key points

  • Herpes meningoencephalitis is an infection of the brain and brain covering (meninges) caused by the herpes simplex virus. It is a medical emergency that requires treatment right away.
  • Symptoms can include headache, fever, changes in consciousness, confusion, neck stiffness, sensitivity to light, seizures, and changes in mood, personality, or behavior.
  • Treatment is with antiviral medicine, sometimes along with other medicines such as steroids and drugs to prevent seizures.

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.
Online Medical Reviewer: Berry, Judith, PhD, APRN
Online Medical Reviewer: Marcellin, Lindsey, MD
Date Last Reviewed: 11/20/2013
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