What are the meninges?
As a protective membrane, the three-layered meninges (made up of the pia mater, dura mater, and arachnoid mater) prevent infectious materials from coming into contact with the central nervous system (brain and spinal cord), protect the all-important brain and spinal cord from injury, and provide a space where cerebrospinal fluid (CSF) circulates. The brain essentially “floats” in a sea of cerebrospinal spinal fluid between two layers of the meninges, and this provides shock absorption for this most essential of organs.
Bacterial, Viral & Fungal Meningitis
Meningitis is generally caused by a bacteria, virus or (rarely) a fungus. Determining the cause of the illness is crucial to its proper treatment. Viral meningitis is generally less severe than a bacterial infection, and affected individuals can often recover without specific treatment other than supportive measures.
In terms of bacterial meningitis, an untreated infection can lead to brain damage, hearing loss, learning disabilities, and death. Prior to 1990, Haemophilus influenza Type B (HiB) was the leading cause of bacterial meningitis, but the introduction of the HiB vaccine has significantly decreased the frequency of this type of bacterial meningitis. Streptococcus pneumoniae and Neisseria meningitidis are now the most commonly detected bacteria causing worldwide cases of bacterial meningitis.
Viral meningitis (also known as “aseptic meningitis”) is very rarely fatal in persons with normal immune function, but can be dangerous for the young, the elderly, and those with compromised immunity.
Fungal meningitis is rare and usually the result of spread of a fungus through blood to the spinal cord. It is not contagious, and although anyone can get fungal meningitis, people with weak immune systems, like those with AIDS or cancer, are at higher risk. The most common cause of fungal meningitis for people with weak immune systems is Cryptococcus. This disease is one of the most common causes of adult meningitis in Africa.
Signs and Symptoms of Meningitis
The cardinal symptoms of meningitis are headache, stiff neck, and high fever. Symptoms can also include nausea, vomiting, confusion, lethargy, sleepiness, seizures, and photophobia (pain and discomfort when looking at bright lights). Infants with meningitis may not demonstrate symptoms of stiff neck, fever and headache, but may show signs of lethargy, difficulty waking, irritability, vomiting and loss of appetite.
Meningitis is diagnosed by obtaining a sample of cerebrospinal fluid via a procedure known as a “spinal tap”. During a spinal tap, a needle is inserted into the spine and CSF is extracted from the space between two layers of the meninges. The sample of is then sent to a laboratory where the cause is then identified.
When bacterial meningitis is diagnosed, antibiotics are prescribed for the specific organism identified in the laboratory. According to the Centers for Disease Control, proper treatment with appropriate antibiotics reduces mortality from bacterial meningitis to less than 15%.
If viral meningitis is diagnosed, doctors usually recommend bed rest, fluids, and medicine to relieve headache and fever.