Types of meningitis | The Different Types of Meningitis

Meningitis occurs due to various causes, and identifying the type and cause of meningitis is the first step towards an effective treatment.

The types of meningitis are classified into different categories according to the causative agents:

1- Bacterial meningitis:

Bacterial meningitis is the term referring to bacterial inflammation of protective membranes covering the brain and spinal cord, the meninges, usually by bacterial invasion of the fluid surrounding the brain and spinal cord, causing a characteristic swelling of these membranes.

Despite being life-threatening, bacterial meningitis is not the most frequent type of meningitis, thanks to childhood vaccination in the past few decades. This refers to an incidence rate of 1.3 per 100,000 persons in the United States.

Causes:

According to the patients’ age group, bacterial meningitis occurs due to infection by a wide variety of bacterial species.

The most frequent causes are Streptococcus pneumonia, Group B Streptococcus, Neisseria meningitides, Haemophilus influenza, and Listeria monocytogenes.

What makes someone at a higher risk of getting bacterial meningitis?

Age: Although people can develop bacterial meningitis at any age, young children are at higher risk due to immune immaturity. Thanks to the introduction of conjugate vaccines in the past few decades, the rates have dropped tremendously. While previously bacterial meningitis was a disease of children and adolescents, currently, most patients are elderly with an average age of 50, especially for Listeria monocytogenes meningitis.

Living in groups: Bacterial meningitis can spread at ease in overcrowded or densely populated community settings. College campuses, dormitories, military bases, and retirement houses are the usual places. This is more frequent with meningococcal meningitis, caused by Neisseria meningitides.

Certain medical conditions: Pulmonary diseases, malignancies, chronic sinusitis, chronic middle ear inflammation (otitis media), and immunity problems, for instance, HIV infections, diabetes mellitus, cancer, or the use of immunosuppressive drugs, are all risk factors for bacterial meningitis.

Patients who underwent splenectomy (surgical removal of the spleen) are at significant risk for S. pneumoniae and Haemophilus influenzae meningitis since the spleen is the only site in the human body where encapsulated bacteria; such as S. pneumoniae, can be cleared from the bloodstream.

Recent cranial neurosurgery may increase the risk of meningitis, known as (postoperative meningitis).

Pregnancy: Pregnant females are at higher risk for Listeria monocytogenes infection, causing meningitis, miscarriage, stillbirth, and premature delivery.

Travel: Traveling to crowded locations, for instance, Mecca during pilgrimage seasons, facilitates the spread of meningococcal meningitis between pilgrims. Therefore, vaccination is mandatory by law before the pilgrimage.

Sub-Saharan Africa is called the meningitis belt, and traveling there during the dry seasons increases the risk of meningococcal spread, too.

Genetic factors: It’s believed that the risk of getting meningococcal and pneumococcal diseases, disease outcomes, and increased disease severity run in families. Specific genes that control the immune response to bacterial invasions have protective roles in ordinary people deficient in the absence of these genes.

Certain factors in neonates and infants: Preterm labor, Down syndrome, and congenital heart diseases are linked to increased risk of bacterial meningitis.

Vaccination: The US centers of disease control and prevention (CDC) recommend Meningococcal vaccines, Pneumococcal vaccines, and Hib vaccines for children and adults on schedule for maximal protection from bacterial meningitis.

Vaccination of pneumococcal meningitis patients also reduces the risk of second meningitis episodes.