Wednesday, 17 September 2014

What is meningitis?

Adventure racer Rika Viljoen is currently in hospital with bacterial meningitis and like the rest of the the AR community, I've been reading up on this illness. This piece that I've written should answer your questions around how Rika got bacterial mengitis.

You've probably heard of meningitis and know that it has something to do with an infection and the brain and that it generally is not a good thing to have. You're right. And that's essentially what it is - an infection of the brain.

The most common symptom is a headache and a stiff neck; those affected can't tip their head forward to touch their chin to their chest.

Fever (increased body temperature caused when the body sends out the artillery to deal with the invaders), confusion or altered consciousness, vomiting, and an inability to tolerate light or loud noises are also symptoms.

There are two common agents that cause infection - viruses and bacteria. And it isn't any one specific virus or bug (bug is lingo for bacteria); a variety of each are responsible. Parasites, funguses and non-infectious agents (like cancer, cysts and certain drugs) can also be responsible.

On the virus front, enteroviruses (responsible for a range of diseases including polio, chronic fatigue syndrome and non-specific illnesses where fever, headache, sore tummy, sore throat and muscle pain are symptoms), herpes simplex 2 (genital herpes), the chicken pox and shingles virus, mumps virus, HIV and a virus carried by rats that literally goes straight to the head of the infected person.

In adults, the bacteria Neisseria meningitidis (also known as meningococcus) and Streptococcus pneumoniae (also known as pneumococcus) together cause 80% of bacterial meningitis cases.

Meningococcus live in the nose and throat of 5-15% of adults as part of the normal flora, causing no trouble.
Pneumococcus also just hangs around and you can have it and not be ill. It's the fellow responsible for causing pneumonia and when you're susceptible (lowered immunity, elderly, children) then it takes advantage of the situation to cause a range of illness from a snotty nose to a sinus infection, middle-ear infection, pink eye to pneumonia.

It's important to diagnose what has caused the meningeal infection because treatment needs to be specific for the organism. First treatment line is antibiotics (for meningitis caused by bacteria) and antiviral medications (for meningitis caused by viruses).

We're invaded by a multitude of viruses and bugs all the time and just because you have flu or a sinus infection it doesn't mean that you'll develop meningitis.

There are three membranes that surround and protect the brain and spinal cord. These are called the meninges.

So looking at the three layers there's a soft, form-fitting base layer (against the brain - capillaries penetrate this layer), a light-weight, loose-fitting waterproof shell and a storm-weather, thick and durable waterproof jacket (below the skull). Fluid (Cerebrospinal Fluid - CFS) flows in the space (subarachnoid space) between the loose-fitting shell and the base layer.

And then there's this wonderful mechanism called the blood-brain barrier (BBB). More than 100 years ago it was found that if a blue dye was injected into the bloodstream of an animal, if showed up in tissues of the whole body except the brain and spinal cord.

Infectious agents have to get through the meninges or BBB into the CFS to cause meningitis, which is an infection specifically of the loose-fitting shell (arachnoid mater) and the form-fitting base layer (pia mater) of these layers as well as the actual brain tissue, which become inflammed.

With is being not-so-easy for bacteria to get into the meninges and CFS, how do they do so?

They gain access either through the bloodstream or by direct contact with the CSF and meninges via the nasal cavity or skin. Invasion of the bloodstream is most common. You need to have head trauma (injury / skull fracture) or an infection of the throat or sinuses that has made contact with the subarachnoid space.

On Friday, while at work (she's a school teacher), the first sign for Rika that something was wrong was that she had a really bad headache and her vision was affected to the extent that she couldn't see properly. She was taken straight to casualty by a colleague. The hospital sent her home having diagnosed a sinus infection. On Friday night she was in pain and not doing well. Richard took her back to the hospital.

I think meningitis was confirmed on Saturday (lumbar puncture is performed to extract CSF) and treatment initiated.

And this is the key element here: sinuses are one way for bacteria to get into the CFS.

Sinuses are air-filled spaces around the nasal cavity. There are four of them. Many major blood vessels, supplying blood to the brain, lie next to the sinuses - and that's how infection is transferred.

You could have a sinus infection every season and never get meningitis. It's really a combination of factors (severe infection in just the wrong place) that results in the conditions that lead to meningitis.

Treatment is specifically geared towards fighting the infection (intravenous antibiotics) and probably also corticosteroids to reduce inflammation and swelling of the meninges and resulting pressure on the brain. Sedation is common practice.

Bacterial meningitis is a very serious illness and Rika has a battle on her hands. Being young, fit and healthy is a big positive in her arsenal in her fight against this infection.

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