The first time I had a patient with herpes simplex virus infection of the brain was while I was doing my Infectious Diseases (ID) fellowship. It was a woman who had neurosurgery to remove a brain tumor.
She was more than a week into her recovery from surgery but suddenly one day, she was confused and had a low grade fever. As part of the investigations, her spinal fluid was tested. The suspicion was that she had a bacterial infection in the brain due to contamination from her recent surgery. Lo and behold, the spinal fluid came back positive for herpes simplex virus!
Over the past 3 years, I have had 4 cases of proven HSV meningitis.
1 – One was a 50 something woman who came to the ER because of severe headache, neck stiffness, sensitivity to light, and nausea.
2 – Another was a 30 something man with severely uncontrolled diabetes, who also came with headache, along with neck pain and sensitivity to light.
3 – Yet another was a 70 something man with dementia who presented with worsening confusion and low grade fever.
4 – The last case was a 40 something woman with diabetes who presented with severe worsening headache, neck pain, nausea, vomiting, sensitivity to light, and low grade fever.
Meningitis is an infection of the membranes (meninges) lining the brain. An infection of the central nervous system can also involve the substance of the brain. That is called encephalitis, and with this, there tends to be more confusion, and decreased level of consciousness. Sometimes a patient can have both meningitis AND encephalitis. This is referred to as meningoencephalitis.
So yes…herpes simplex virus (HSV) can indeed cause infection of the brain and it’s lining. Fortunately, however, HSV is not a common cause of meningitis. Of all the cases of viral meningitis, only about 0.5 to 3% of them are due to HSV.
When HSV meningitis is diagnosed, the affected person is usually astonished, devastated even. They can’t believe that what they thought was “just an STD that happens in other people” is the cause of their meningitis. Then the spouse (if there is one) starts to panic about their risk of “catching” herpes.
What is herpes?
Herpes, as mentioned in this earlier post, is the broad term for a family of viruses which, after acquisition, can never be eradicated (cured), but stay dormant in the body forever. Herpes simplex viruses (HSV) hide out in the nerve roots, and during times of stress, can reactivate causing recurrent infection.
Related post: Yes, you probably have herpes
If tested, many of us would be found to have evidence of having been exposed to at least one type of HSV in the past. Notably, as many as two-thirds of people don’t manifest any symptoms when they first get infected with HSV. Many will go through life without ever developing an outbreak of infection.
There are two types of HSV: type 1, and type 2. Classically, HSV type 1 causes fever blisters (on the lips or in the mouth), and HSV type 2 causes genital herpes. However, either type can cause infection about the mouth or the genital area, and either type can cause meningitis. Of the 5 patients I’ve had with HSV meningitis, 3 of them were caused by HSV type 2.
How on earth can herpes cause infection of the brain?
HSV lays dormant in nerve roots. When it reactivates, it travels along the particular nerve, causing an outbreak of blisters in then area of skin supplied by that nerve. If the virus happens to be hiding out in the root of a nerve in the head and neck area, then reactivation can lead to extension of the virus into the brain, causing meningitis.
Of all the people having HSV dormant in their bodies, there is no way to tell who would reactivate. Generally speaking however, a strong immune system goes a long way in decreasing the chance of reactivation.
What is the treatment of HSV meningitis?
Patients sick enough to be admitted to the hospital are usually treated with an antiviral medication (acyclovir) intravenously. Truthfully, most patients will recover on their own, and antiviral treatment is not compulsory. This is reassuring, especially for persons living in resource limited settings. Having practiced in the Caribbean, I know that confirmatory testing for HSV meningitis is not readily obtainable. Furthermore, antiviral medication is very expensive and may not always be available.
Patients with HSV encephalitis on the other hand, are sicker, and antiviral treatment is definitely indicated in those cases. Sometimes these patient are so sick that they can develop seizures, and sometimes even have strokes.
Prevention of HSV meningitis
There is no specific preventative measure for HSV meningitis. From the cases described earlier, you will notice that they all had some factor contributing to a weakened immune system – recent major surgery, diabetes, elderly.
As with other infectious diseases, general optimization of health status goes a long way to improve the immune system and decrease chances of severe infections.
Thankfully, HSV meningitis and encephalitis are uncommon infections and most of us will never have to battle with them.