1. Meninges are three layers of membranes that cover and protect brain and spinal cord
(your central nervous system [CNS]). They’re known as:
1. Dura mater: it is the outer layer, closest to the skull.
contains a drainage system, called the dural venous sinuses,
which allows blood to leave brain and allows cerebrospinal
fluid to re-enter the circulation.
dura mater receives its blood supply from middle meningeal
artery and vein, and your trigeminal nerve runs through it.
2. Arachnoid mater: This is the middle layer..
3. Pia mater: is the inner layer, closest to brain tissue.
Many blood vessels pass through this layer to supply brain tissue
with blood
the arachnoid mater and pia mater are called leptomeninges.
Their function is :
protect and anchor your brain and provide a support system for blood vessels, nerves,
lymphatics and the cerebrospinal fluid that surrounds your central nervous system.
2. spaces within the meninges:
1. The epidural space:- is a space between skull and dura mater.
2. The subdural space :- is a space between dura mater and arachnoid mater. Under
normal conditions, this space isn’t a space, but can be opened if there’s trauma to
your brain (such as a brain bleed) or other medical condition.
3. The subarachnoid space :- is a space between your arachnoid mater and pia
mater. It’s filled with cerebrospinal fluid.
3. • Meningitis is an infection of the protective membranes that surround the brain and spinal
cord (meninges).
• It can affect anyone, but is most common in babies, young children, teenagers and young
adults
• It can cause life-threatening blood poisoning (sepsis) and result in permanent damage to
the brain or nerves.
4. 1) Bacterial meningitis
o Streptococcus pneumoniae
o Group B Streptococcus
o Neisseria meningitidis
o Haemophilus influenzae
o Listeria monocytogenes
o Escherichia coli
o Mycobacterium tuberculosis,, is a less common cause of bacterial meningitis
(called TB meningitis).
• Group B Streptococcus and E. coli: Mothers can pass to babies during birth.
• H. influenzae, M. tuberculosis, and S. pneumoniae: these bacteria spread by coughing or
sneezing while in close contact with others
• N. meningitidis: People spread these bacteria by respiratory or throat secretions (saliva or
spit). This typically occurs during close (coughing or kissing)
• E. coli: People can get these bacteria by eating food prepared by people who did not wash
their hands well after using the toilet.
5. 2) Viral meningitis: -
Non-polio enteroviruses are the most common cause of viral meningitis it can be
found in an infected person’s
o feces (stool)
o eye, nose, and mouth secretions (such as saliva, nasal mucus, or sputum)
o blister fluid
Mumps virus spreads through direct contact with saliva or respiratory droplets
from the mouth, nose, or throat
Herpesviruses, including Epstein-Barr virus, herpes simplex viruses, and varicella-
zoster virus (which causes chickenpox and shingles)
Measles virus
Influenza virus
Arboviruses, such as West Nile virus West Nile virus is most commonly spread to
people by the bite of an infected mosquito.
Lymphocytic choriomeningitis virus spreads through direct contact with saliva
or respiratory droplets from the mouth, nose, or throat
6. 3) fungal meningitis include:-
o Cryptococcus.
o Histoplasma
o Blastomyces
o Coccidioides
o Candida.
4) Parasitic meningitis:- called eosinophilic meningitis
o can be caused by a tapeworm infection in the brain or cerebral malaria.
o Amoebic meningitis is a rare type that is sometimes contracted through
swimming in fresh water and can quickly become life-threatening.
5) Other meningitis causes
o Meningitis also can result from noninfectious causes. They include chemical
reactions, drug allergies, some types of cancer and inflammatory diseases
such as sarcoidosis.