What is Meningitis?
Meningitis is an inflammation of the membranes (meninges) of the brain and spinal chord. It is usually caused by infections of viral, bacterial, or fungal origin. Meningitis caused by bacterial infections is the most serious type, and can be fatal.
In the past, most meningitis cases were found in children under 5 years old. However, due to pervasive vaccination programs, childhood cases have decreased, and the 15-24 year old age group is now at greatest risk. Older adults also develop more cases of meningitis nowadays than young children.
Perhaps an overview of how the brain functions will help to understand meningitis better. The brain and its related tissues and organs make up a very complex but fragile system. Brain tissue is unique in that once brain cells are killed, the body cannot replace them. Therefore, infections affecting the brain are very serious and damage cannot be reversed.
The meninges, which encase the brain and spinal chord, are actually composed of a set of three layered tissues:
- The dura is the tough outer skin of the meninges. It is directly attached to the inner surface of the skull.
- The arachnoid is the middle layer, and is involved in the flow of the cerebrospinal fluid (CSF). CSF is a fluid that lubricates, protects, and gives nutritional support to the brain and spinal chord. It is produced deep inside the brain.
- The pia is the innermost layer, and it gives blood vessels critical access to the brain.
- There is a space between the arachnoid and the pia that is filled with CSF and acts as a “shock absorber” to protect the brain. This area is rich in blood vessels, which help to regulate the amount (and pressure) of CSF. There is a delicate balance between CSF produced and CSF reabsorbed by the brain through these blood vessels.
I went into this cerebral anatomy lesson simply to make the point that anytime there is infection and subsequent swelling in the brain, this delicate balance can be disturbed with serious consequences. The brain is enclosed in the hard bony case of the skull. When it swells too much, it has nowhere to go, and tissues can be damaged or destroyed as they are pushed against the skull. Therefore, any infection or potential swelling of the brain is a very serious matter.
Proper functioning of the brain is also very dependent on its own chemical balance. Sometimes infections can alter the chemistry of the brain and cause dysfunction. Certain substances such as oxygen, glucose, sodium, potassium, carbon dioxide, and others are must be kept at proper levels to have normal brain function. In addition, toxins must be kept out of the brain to avoid chemical imbalance.
Our creator designed our brains to carefully monitor and maintain these delicate balances. There is a layer of cells nearest the capillaries of the brain that act as a filter to let nutrients in and keep toxins and potential infectious agents out. It is referred to as the blood-brain barrier. When this is functioning properly, balance is maintained. However, whenever there is swelling in or around the brain, problems can arise. That is why conditions such as meningitis are so critical.
What Causes Meningitis?
I think the best way to tackle this question is to break down meningitis by the various types of infections that cause most cases.
While bacteria do not cause the majority of meningitis cases (that dubious distinction belongs to viruses), they are definitely responsible for the most serious and life-threatening ones. There are several strains that cause most bacterial meningitis:
- Streptococcus pneumoniae (pneumococcus): This is responsible for most meningitis cases found in infants and young children here in the United States. This strain is often associated with simultaneous ear infections. In fact, this same bacterium can cause pneumonia, as well as ear and sinus infections.
- Neissera meningitides (meningococcus): This is the most contagious form of bacterial meningitis, and often causes epidemics. College students living in dorms, children in daycare centers, and residents of military bases are particularly susceptible to this strain. It often develops as a result of an upper respiratory infection caused by this bacterium.
- Haemophilus influenzae (haemophilus): Used to be the leading cause of bacterial meningitis, but since the 1990’s it has been vaccinated against. Also is associated with upper respiratory infections.
- Listeria monocytogenes (listeria): This strain is found commonly in soil, dust, and contaminated foods such as lunchmeats, hot dogs, and some cheeses. Many wild and domestic animals carry listeria. While most healthy people ever get meningitis from this, it can be deadly to infants and newborns. Infected pregnant mothers can pass it to their fetuses, resulting in a stillborn baby or death of the child shortly after birth.
Viruses are the culprits behind the majority of meningitis cases. Most instances of viral meningitis are mild (relatively, as compared to bacterial) and short-lived. Viral meningitis usually runs its course in about 10 days. The majority of viral cases, up to 90%, are caused by a family of viruses calledenteroviruses. These are also responsible for stomach flu.In fact, the typical symptoms are very flu-like: joint and body aches, sore throat, and potentially severe headaches. Other viruses can cause meningitis as well, including West Nile, mumps, measles, rabies, chickenpox, and others.
While relatively rare, this form of meningitis can be particularly hazardous to those with a compromised immune system. AIDS patients can develop a fungal meningitis called cryptococcal meningitis which can be fatal if not treated with antifungal drugs.
There are a small majority of meningitis cases that are not caused by an infection. Some of these are caused by side effects of chemotherapy, bleeding in the meninges, some types of cancer, immune system disorders, inflammatory diseases such as lupus, and drug allergies. Also, injuries and certain surgical procedures can allow for bacteria and viruses to travel into the meninges in unusual ways. For example, a skull fracture or a cranial stint for draining fluids such as CSF can create an abnormal pathway for microorganisms to breach the blood-brain barrier and cause infections leading to meningitis.
What Are the Symptoms of Meningitis?
As we stated above, viral meningitis is usually no worse than a bad case of the flu. It is generally not considered dangerous in otherwise healthy people. Bacterial meningitis is the one that we must be very aware of and treat with great caution. Some bacterial meningitis can come on very quickly and intensely, and may even lead to coma and death within 24 hours or less! What are the signs to watch out for? Typical symptoms include:
- High fever
- Severe headache
- Stiff neck
- Sensitivity to light
- Confusion and disorientation
- Inability to keep eye contact (especially in very young children)
- Loss of appetite (for food and drinks)
- Skin rash (only with viral or meningococcal cases)
Additional signs that often accompany meningitis or other serious infections in the early stages are: ice-cold hands and feet, leg pain, and extreme paleness. Be especially cautious if you notice these symptoms.
If you suspect bacterial meningitis, get immediate medical attention. I am not a big fan of antibiotics. They are often over prescribed, and there are other options for less critical situations. But bacterial meningitis is a serious condition that can turn fatal very quickly. Rapid treatment with antibiotics can save the patients life and/or prevent permanent damage that will handicap them forever. Many times antibiotics at high doses are administered intravenously to attack the infection as quickly as possible. Every minute counts with brain infections like meningitis. We discussed the blood-brain barrier and how efficient it is at protecting the brain. One of the reasons intravenous medication is sometimes given is because the blood-brain barrier will do its job so well that it won’t let oral antibiotics through to fight the infection.
Bacterial meningitis is very dangerous to infants and small children. One of the problems is that they cannot readily communicate their symptoms. The immune system of newborns is not developed enough yet to spawn a fever in reaction to many infections. Often the only observable symptoms of meningitis in a very young child are seizures or muscle spasms called opisthotonos. This is a hypertension that stiffens the child’s entire body. They also may cry constantly, be unusually sleepy, and have a poor appetite. Brain damage or death may quickly occur unless treatment is obtained ASAP. Untreated meningitis can lead to a slew of problems later in life, such as kidney failure, deafness, blindness, dumbness, learning disabilities, seizures, and behavioral problems.
How is Meningitis Diagnosed?
Often in less serious cases, such as viral meningitis, testing will begin with a throat culture to check for bacterial or viral microorganisms. If meningitis is suspected, simple x-rays may or may not reveal swelling or inflammation in the skull or sinuses. Another test called polymerase chain reaction analysis(PCR) uses DNA to track the presence of certain causes of meningitis.
The most definitive test for meningitis, and according to some the most dangerous, is called a Lumbar Puncture (LP), or “spinal tap.” A very thin needle is inserted into the spinal chord and CSF is drawn off for analysis. Much can be told by looking at the condition of the CSF. Most meningitis patients will have low glucose levels, elevated white blood cell count, and elevated protein levels. In bacterial cases, the specific bacterium can also often be identified. This helps your health care provider to prescribe the most effective antibiotic.
The risk can be huge with an LP. First of all, like with many invasive procedures, the skill of the technician performing the spinal tap has a lot to do with the level of safety. The first thing that is always done upon insertion of the needle is to get a reading of the pressure within the brain-spinal chord system. If it is too high, perhaps due to excessive cranial swelling, CSF is not withdrawn because to do so could cause herniation of the brain stem. This is can lead to breakdown of critical body functions such as respiration and heartbeat, and sudden death.