Meningitis is an inflammation of the leptomeninges and underlying subarachnoid cerebrospinal fluid (CSF).

Meningitis is the inflammation of the protective membranes covering the central nervous system, known collectively as the meninges. Meningitis is a disease involving inflammation, or irritation, of the meninges. Most cases of meningitis are caused by microorganisms, such as viruses, bacteria, fungi, or parasites, that spread into the blood and into the cerebrospinal fluid (CSF). Many of the bacteria or viruses that can cause meningitis are fairly common and are more often associated with other everyday illnesses. Sometimes, however, they spread to the meninges from an infection in another part of the body. The meninges are composed of three layers of membranes enclosing the brain and spinal cord. Pia mater is the innermost layer. It is akin to a tissue paper that closely adheres to the brain and spinal cord, dipping into the various folds and crevices. Arachnoid mater is the middle layer. It is a filmy membrane that is joined to the pia mater by fine threads resembling a cobweb.

Dura mater, a parchment-like membrane, lies on the outermost part of the meninges and adheres to the skull and spinal canal. The cerebral spinal fluid (CSF) is the fluid that circulates in the spaces in and around the brain and spinal cord. In the past, most meningitis cases occurred in children younger than 5 years. But as a result of the protection offered by current childhood vaccines, most meningitis cases now occur in young people between the ages of 15 and 24. Older also tend to have a higher incidence of meningitis than do young children. Bacterial meningitis is less common than viral meningitis but is usually much more serious and can be life-threatening if not treated promptly.

Many different types of bacteria can cause meningitis:

• Group B Streptococcus.
• Escherichia coli.
• Listeria monocytogenes.

These are the most common causes of meningitis in newborns. It's also possible to get viral meningitis as a complication of chickenpox, but this is also very rare in healthy kids.

Meningococcal meningitis is endemic in parts of Africa, India, and other developing nations. Bacterial meningitis is contagious, which means it can be passed to someone else by spit or snot.

Symptoms in infants under 12 months include:

• high fever
• fretfulness
• irritability - particularly when handled
• difficulty awakening
• drowsiness
• difficulty feeding
• a stiff neck
• bulging fontanelle

Meningitis also can lead to skin rashes, although rashes caused by bacterial meningitis look different from those caused by viral meningitis. Immunosuppressed patients are at increased risk of opportunistic infections and acute bacterial meningitis. Immunosuppressed patients may not show dramatic signs of fever or meningeal inflammation. Complications of bacterial meningitis may require specific treatment. Rest, fluids, and good nutrition, as well as measures to control fever and relieve pain, will ease discomfort and aid in recovery from viral meningitis. Drugs such as dexamethasone (a steroid, different from the steroids abused by bodybuilders, that can reduce swelling of the brain) are sometimes given to reduce inflammation or to reduce the chance, or spread, of septicemia.

Treatment for Meningitis

• Acute bacterial meningitis requires prompt treatment with intravenous antibiotics to ensure recovery and reduce the risk of complications.
• Pneumovax (also known as Prevenar) against Streptococcus pneumoniae is recommended for all people 65 years of age or older.
• Drugs such as dexamethasone are sometimes given to reduce inflammation or to reduce the chance, or spread, of septicemia.
• Antifungals to combat the infection are usually administered, as well as fluids and medicine to control pain and fever.