CAUSATIVE MICROORGANISMS Escherichia coli and the group B streptococci in neonates Streptococcus pneumoniae and Neisseria meningitidis in adolescents and young adults Listeria monocytogenes in the elderly

1. MENINGITIS
ASSISTANT PROFESSOR
DEPARTMENT OF PATHOLOGY

2. PORTALS OF ENTRY OF INFECTION INTO CNS
• Hematogenous spread –Most common
• Direct implantation- Traumatic or congenital malformations (e.g.,
meningomyelocele)
• Local extension can originate from infected adjacent structures,
such as air sinuses, teeth, skull, or vertebrae.
• Viruses - Rabies and herpes zoster viruses.

3. INTRODUCTION
• Leptomeningitis- Inflammation of subarachnoid and pia
• Meningitis –Inflammation of leptomeninges and CSF within
the subarachnoid space.
• Meningoencephalitis- Inflammation of meninges and brain
parenchyma

4. ETIOLOGY
• Infective – Septic, Aseptic
• Chemical – Drugs
• Carcinomatous-Metastasis

5. ACUTE PYOGENIC MENINGITIS

6. CAUSATIVE MICROORGANISMS
• Escherichia coli and the group B streptococci in neonates
• Streptococcus pneumoniae and Neisseria meningitidis in
adolescents and young adults
• Listeria monocytogenes in the elderly

7. CLINICAL FEATURES

8. CSF

9. CSF
• Cloudy or frankly purulent CSF
• Many as 90,000 neutrophils per cubic millimeter
• Increased protein concentration, and markedly reduced glucose
content.

10. PYOGENIC MENINGITIS

11. MORPHOLOGY
• The anatomic distribution of the exudate varies; in H. influenzae
meningitis it is usually basal
• Pneumococcal meningitis it is often dense over the cerebral
convexities near the sagittal sinus.

12. MICROSCOPY
• Neutrophils fill the subarachnoid space in severely affected areas
and are found predominantly around the leptomeningeal blood
vessels in less severe cases.
• Gram stain reveals variable numbers of bacteria.

13. MICROSCOPY

14. COMPLICATIONS
• Ventriculitis
• Phlebitis Venous occlusion Hemorrhagic infarction of underlying brain
• Leptomeningeal fibrosis Hydrocephalus
• Septicemia hemorrhagic infarction of adrenal glands and cutaneous petechiae(
Waterhouse Friedrichsen syndrome)
• Focal cerebritis and seizures
• Cerebral abscess
• Chronic adhesive arachnoiditis

15. ACUTE ASEPTIC (VIRAL) MENINGITIS

16. ASEPTIC VIRAL MENINGITIS
• Aseptic meningitis is a misnomer
• It is a clinical term used for an absence of organisms by bacterial
culture
• Manifestations of meningitis, including meningeal irritation, fever,
and alterations of consciousness of relatively acute onset.

17. CSF
• Less fulminant than that of pyogenic meningitis
• CSF is sterile
• Increased number of lymphocytic (pleocytosis)
• The protein elevation is only moderate, and the glucose content is
nearly always normal.

18. ETIOLOGY
• Enterovirus (80%)
• An aseptic meningitis-like picture may also develop subsequent to
rupture of an epidermoid cyst into the subarachnoid space or the
introduction of a chemical irritant (chemical meningitis).

19. MORPHOLOGY
• No distinctive macroscopic picture except for brain swelling seen
only in some instances
• On microscopic examination there is either no recognizable
abnormality or mild to moderate infiltration of the leptomeninges
by lymphocytes

20. COURSE OF DISEASE
• Usually self-limited
• Treated symptomatically

21. FUNGAL MENINGITIS
• Primarily in immunocompromised individuals.
• Hematogenous dissemination of fungi;
• The most frequent offenders are Candida albicans, Mucor species,
Aspergillus fumigatus, and Cryptococcus neoformans

22. MORPHOLOGY
• The three main forms of injury in CNS fungal infection are
chronic meningitis, vasculitis, and parenchymal invasion.
• Vasculitis- Mucormycosis and Aspergillosis

23. CRYPTOCOCCAL MENINGITIS
• Most common opportunistic infection
• May be fulminant and fatal in as little as 2 weeks or indolent,
evolving over months or years.

24. CSF
• The CSF may contain few cells but usually has a high
concentration of protein.
• The mucoid-encapsulated yeasts can be visualized in the CSF with
special stains or detected indirectly using assays for cryptococcal
antigens

25. GROSS

27. TUBERCULOUS MENINGITIS
• Tuberculosis of the CNS may be part of active disease elsewhere in
the body, or appear in isolation following seeding from silent
lesions elsewhere, usually the lungs.

28. CSF
• Pleocytosis made up of mononuclear cells or a mixture of
neutrophils and mononuclear cells
• Protein concentration (often strikingly so), and a moderately
reduced or normal glucose

29. GROSS

30. MICROSCOPY

31. TUBERCULOMA

32. TUBERCULOMA
• Well circumscribed intraparenchymal mass
• Rupture of tuberculoma into subarachnoid space cause Tuberculous
meningitis
• Tuberculoma maybe upto several centimeters causing significant mass
effect
• Always occurs after hematogenous dissemination of organism from
pulmonary infection.

33. COMPLICATIONS
• Fibrous adhesive arachnoiditis
• Obliterative endarteritis
• Hydrocephalus

34. CSF