Shingles Encephalitis
EDP column by Dr Ketan Dhatariya

“My uncle had shingles recently and even though he is physically better, his behaviour is different to before. Why is this?"

Shingles is a blistering rash that is caused by the same virus that causes chicken pox – the varicella virus. In fact, you can only get shingles if you have had chicken pox in the past – even if it was decades ago. The chicken pox virus has the ability to lie dormant within certain areas of the nervous system. Eventually, the virus come back to life and spreads along the nerves that it has been living in causing symptoms. No one knows why the virus comes back to life. Usually the precipitating factor is a decrease in your body's natural resistance, which may come through other infections, stress, being generally run down.  Being on certain medicine may also increase the likelihood of getting shingles.

Because the virus lives in the nervous system, it can occasionally affect the brain. If this happens, it is known as varicella encephalitis. Thankfully this condition is relatively rare because it can be quite serious. People who have had shingles who then, a few days later develop symptoms that include confusion, irritability, drowsiness or vomiting. Weakness or inability to walk, severe headache and neck stiffness are also possible features. If any of these develop, then it is important to get them to a hospital quickly to get the proper diagnosis made and then start the correct treatments.

The diagnosis will be made by taking off some of the fluid that surrounds the brain by doing a lumbar puncture (a small needle going into the lower back). The fluid is analysed to see what the cause of the problem is.

The virus can affect different parts of the brain, including the parts that control personality. Occasionally before the virus is completely killed off by the treatment, these parts of the brain can be damaged. This leads to the person having a different personality to the one they had before they became unwell. In children this condition can be very serious, with about 1 child developing encephalitis for every 50,000 children who get chicken pox. Because of this risk, in the United States, the vaccine against chicken pox is given to all children as part of the routine immunisation schedule.