Infections Of The Nervous System
by Dr. John Rees
This month Dr Rees tells us about infections of the Nervous System and how they fall into three groups
Broadly, infections of the nervous system affect the meninges (the brain coverings), or encephalitis (the brain itself), frequently both and fall into three groups; bacterial, viral and other rarer causes.
The symptoms common to both conditions include fever, severe headache, sensitivity to light, confusion and in the case of encephalitis, impaired consciousness, epilepsy and occasionally symptoms masquerading as a stroke.
Urgent diagnosis including lumbar puncture, blood tests and brain imaging is essential especially in children, to distinguish between bacterial and viral causation because bacterial infection requires immediate life-saving antibiotics, whereas it is only rarely that viral infections can be given specific antiviral medicines.
Meningitis is usually caused by one of three common bacteria and one rare one (TB), all of which are now largely preventable by immunisation or easily treated by antibiotics, recognising the threat from antibiotic resistance. Before antibiotics, these infections were often, and in the case of TB invariably, fatal. Encephalitis spreads from the meninges into the brain and a Brain Abscess can be caused by different bacteria arriving in the brain via the blood stream or spreading directly from an infected sinus or mastoid infection. Death from meningitis is fortunately rare but brain abscess still carries a high mortality in 2018 and frequent problems for the survivors.
Encephalitis is usually caused by viruses the most common being measles and mumps which are uncommon in developed societies with good immunisation programmes but very common worldwide. The lack of immunisation take-up by some parents is worrying and has increased the incidence of these two diseases with the associated risk of encephalitis. In some parts of the world there are specific viruses that cause encephalitis, often seasonally. The most severe encephalitis is caused by the herpes simplex virus with a high degree of mortality or poor recovery in spite of the availability of specific anti-viral drugs.
Some rare forms of encephalitis can occur in association with a general infection (usually but not always viral), causing an indirect inflammation of the brain rather than a direct attack by the virus itself. There are also similar conditions when the brain’s interconnecting nerves have their insulating myelin damaged (post infective demyelination). In addition, we are now aware that some cancers and many auto immune conditions (when the body’s defence system attacks itself), can cause an encephalitis like condition.
Many unusual organisms including fungi, protozoa and others can infect people whose immune system is depressed because of disease or medication, for example patients on chemotherapy or with HIV/AIDS. It is important to recognise that many of our infections (especially viral), have or will come from animals e.g. HIV/AIDS, Avian Flu, Ebola.
Malaria remains one of the world’s major killers and cerebral malaria is the most lethal form. It is worrying that the parasite is becoming resistant to the current best anti malarial medication.
With vast numbers of people travelling to all parts of the world we have to be aware of rare causes of meningo-encephalitis.
Help is available from:
- Meningitis Now
- Brain & Spine Foundation