Meningitis refers to inflammation of the membranes (meninges) surrounding the brain and spinal cord. It is generally caused by viral or bacterial infections, though chemical meningitis can occur from injection of irritants into the subarachnoid space. The main types are acute pyogenic (bacterial), aseptic (usually viral), and chronic (often tuberculous or fungal). Common causative agents include bacteria like Neisseria meningitidis, Streptococcus pneumoniae, and viruses such as enterovirus. Bacteria typically enter the CSF through the blood or direct implantation. This causes an inflammatory response and increased CSF pressure that can lead to complications like hydrocephalus or brain damage if left untreated

1. Meningitis
Group- 5 Tutor:Dr.Rajiv Shrestha

2. Group Members
• Sagun Baral
• Ashkal Basi
• Ashutosh Ghimire
• Kamal Ghimire
• Anup Subedi
• Samir Raut
• Prasesh Dhakal
• Prastuti Shrestha
• Saugat Lamichhane
• Kriti Pandey
• Shravya Rayilla

3. What is meningitis??
• Meningitis refers to an inflammatory process of
leptomeninges and CSF within the sub-arachnoid
space.
• Meningitis is generally caused by an infection, but
chemical meningitis may also occur in response to a
bacterial irritant injected into the sub-arachnoid
space.

4. CLASSIFICATION
• Infectious meningitis is broadly classified into three
groups :
- Acute Pyogenic (Bacterial) Meningitis
- Aseptic (usually acute viral) Meningitis
- Chronic (usually tuberculous / fungal) Meningitis

5. CAUSATIVE AGENTS
OF
MENINGITIS

6. - BACTERIAL AGENTS:
Neonatal: E. coli
Group B Streptococci
Infants: Hemophilus influenzae
Adolescents and young adults:
Niesseria meningitidis(most common)
Streptococcus pneumoniae
Elderly: Listeria monocytogens
Streptococcus pneumoniae
- VIRAL AGENTS: Enterovirus(most common), Mumps virus,
Coxsackie virus, HSVII, EBV
- FUNGAL AGENTS: Candida albicans, Cryptococcus neoformans,
Blastomyces dermatidis, Coccidiodesimitis
- PARASITES: Protozoa, Nematodes, Cestodes

7. Routes of Infection :
There are 4 methods by which microbes enter the
nervous system
1. Hematogenous route : through arterial and venous spread;
is the most common route of entry
2. Direct implantation : it may be traumatic or rarely
iatrogenic i.e. through a lumbar puncture needle
3. Local extension : through air sinuses, infected tooth or a
surgical site.
4. Through peripheral nervous system : as occurs with certain
viruses.

8. Pathogenesis of bacterial meningitis:
Nasopharynx
Nasopharyngeal colonisation (in epithelial cells)
Local invasion into intravascular space
bacteria transported across epithelial cells in membrane bound vacuoles
OR by creating separations in apical tight junctions
Bacteremia
(avoid phagocytosis due to presence of polysaccharide capsule)
Reach choroid plexus / Adhere to cerebral capillary endothelium
Bacteria gain access to CSF
Rapid multiplication in CSF
Lysis of bacteria …contd

9. Release of bacterial component Cytotoxic edema
(lipopolysaccharide, endotoxin, peptidoglycan, teichoic acid)
Cerebral microvascular endothelium Macrophages activated
and release cytokines
IL-1,TNF
Increase BBB permeability;
Vasculitis Subarachnoid space inflammation
Vasogenic edema and ↑CSF outflow Exudates
leakage of serum proteins resistance; ↑ICP
into the sub arachnoid space
CSF flow obstruction & Hydrocephalus
↓CSF reabsorption
↓cerebral blood flow
Interstital edema

10. Morphology of Bacterial Meningitis
GROSS:
• Exudates in the
leptomeninges and the surface
of brain.
• Engorged meningeal vessels.
• In H. influenzae exudates are
localized to the base.
• In Pneumococcal meningitis
the exudate is seen over
cerebral convexities near the
sagittal sinus.
• When the meningitis is
fulminant, the inflammation
may extend to the ventricles
producing ventriculitis.
MICROSCOPY:
• Neutrophils fill the entire
subarachnoid space.
• In severe cases they infilterate
the vessel wall and even the
brain.
• Untreated cases can follow
leptomeningeal fibrosis and
hydrocephalus.

11. Acute pyogenic meningitis showing purulent exudates

12. Clinical Features
• Fever, chills and rigor
• Headache, nausea, vomiting
• Seizures, cranial nerve palsies
• Signs of meningeal irritation
– Neck rigidity
– Photophobia

13. Signs

14. Complications:
• Bacterial : - Waterhouse-Friderichsen syndrome
- obstructive hydrocephalus
- chronic adhesive arachnoiditis
- focal cerebritis
- phlebitis leading to venous occlusion and
hemorrage of underlying brain.

15. Cerobrospinal Fluid (CSF) in Normal individuals and in different types of meningitis
Characteristics Normal CSF Acute pyogenic
meningitis
Tuberculous
meningitis
Viral meningitis
Pressure Normal
(<20cm H20)
Highly
increased
Moderately
increased
Slightly
increased
Direct examination
A. Cell
count/cumm and
predominant cell
1-3
Lymphocytes
1,000-20,000
Neutrophils
(90-95%)
50-500
Lymphocytes
(90%)
10-500
Lymphocytes
B. Biochemical
analysis
1. Protein
(mg%)
2. Sugars
(mg%)
30-45
40-80
Highly
increased
(100-600)
Diminished
(10-20)
Moderately
increased
(80-120)
Diminished
(10-20)
Slightly
increased
(60-80)
Normal
Bacteriological examination
A. Microscopy
Gram stain
ZN-staining
Nil
Nil
GPC,GNC,GN
B,GPB etc
Nil
-
Acid fast bacilli
-
B. Culture Nil Specific
medium
In LJ medium Cell cultures

16. References
Harrison’s Principles Of Internal Medicine
Pathologic Basis Of Disease
Robbins and Cotran

17. K YOU
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