“Sickness comes on horseback, but departs on foot” is an old Dutch saying what is so true for neurological infectious diseases. Most of the times you are healthy one day and you have a life treathening illness the next day.

That was the case with the older lady I saw in the Emergency department, when I just started my residency. According to her family she was well the day before, lifed on her own and runned her household herself without any help. One day later her daughter visited her and found her complety desorientated and with trouble speaking. In the emergency department she didn’t had a fever, but was desoriented and had trouble with finding words.  We thought she might had a stroke, made a scan of the head, started therapy and admitted her on the Neurology ward.

One of the reasons why infection of the brain or meninges is so dangerous is because there is only room for your brain and spinal fluid within your bony skull. Tissue with inflammation tends to swell, and the room in your head is limited. This is one of the reasons some patients with infection within the brain die. Another reason is that you need your brain, almost every bit is important, and when a part doesn’t work it is causing problems in other parts of your body: you will have a paresis of an arm and leg, problems with finding words or you have convulsions.

When she came on the Neurology ward, my patient suddenly had an epileptic seizure and she developed a fever. Immediate we had a different diagnosis, this wasn’t a stroke, this was inflammation of the brain caused by the herpesvirus! We performed a lumbar puncture and started aciclovir (a medicine against herpesvirus). In the spinal fluid we found infection cells and after a few days the herpesvirus was also found in the spinal fluid.

Even though the illness “comes by horseback”, a diagnosis can be difficult. An important example is inflammation of the brain caused by a virus, “viral encefalitis”. A patient with this disease is often moderately ill, without high fever and has often a headache. But, most patients also are desoriented and can’t tell about the headache. Also, a lot of other (mostly elderly) patients are desorientated when they have an infection somewhere else in the body, like an urinary tract infection. This is called a delirium. Also a stroke can cause desorientation.

My patient fortunately survived this disease, not all patients do. Unfortunately, she couldn’t live alone anymore and had to go to a nursery home because of epileptic attacks that were hard to treat. This  was a remainder of the inflammation of the brain. Before aciclovir was discovered almost all patients died from herpes encefalitis. Nowadays about 1/3 of the patients die, around 2/3 of the surviving patients have neurological deficits afterwards.

And this is why it is so important to investigate virus infections and try to find ways to prevent these infections. With new medication we might find ways to treat the illness better, when we get more knowledge about how you get ill, we can think of ways to prevent the disease.