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1

With infection, damage to nervous tissue may be the consequence of ____________________

 

  • direct injury of neurons or
  • glia by the infectious agent or
  • may occur indirectly through the elaboration of microbial toxins,
  • destructive effects of the inflammatory response,
  • or the result of immune-mediated mechanisms.

2

There are four principal routes by which infectious microbes enter the nervous
system. 

  1.  Hematogenous spread
  2. Direct implantation of microorganisms
  3. Local extension
  4.  peripheral nervous system

3

_____________ is the most common means of entry; infectious agents ordinarily
enter through the arterial circulation, but retrograde venous spread can occur through
anastomoses with veins of the face
.

Hematogenous spread

4

 Direct implantation of microorganisms is almost invariably
________________

traumatic or is associated with congenital malformations

(such as meningomyelocele).

5

  Local
extension can come from any of several adjacent structures ________________. 

(air sinuses, an infected tooth,
cranial or spinal osteomyelitis)

6

Transport along the peripheral nervous system occurs with
certain viruses, such as______________

 

 

Note :. General aspects of the pathology of
infectious agents are discussed in Chapter 8 ; here we focus on some of the distinctive forms of
CNS infections

 rabies and herpes zoster. 

7

ACUTE MENINGITIS
Meningitis refers to an i

  • Acute Pyogenic (Bacterial) Meningitis
  • Acute Aseptic (Viral) Meningitis

8

What is Meningitis ?

refers to an inflammatory process of the leptomeninges and CSF within the
subarachnoid space,

9

What is  while meningoencephalitis

It combines this with inflammation of the brain
parenchyma.

10

Meningitis is usually caused by an __________, but may also occur in response to a
nonbacterial irritant
introduced into the subarachnoid space (chemical meningitis).

infection

11

 Infectious
meningitis is broadly classified into: 

on the basis of the characteristics of inflammatory exudate on CSF examination and the clinical evolution of the illness.

  •  acute pyogenic (usually bacterial meningitis),
  • aseptic (usually acute viral meningitis),
  • and chronic (usually tuberculous, spirochetal, or cryptococcal)

12

The microorganisms that cause acute pyogenic meningitis vary with the age of the affected
individual
.

In neonates, they include__________ and _________

 

 Escherichia coli and the group B streptococci; 

13

The microorganisms that cause acute pyogenic meningitis vary with the age of the affected individual. In other
extreme of life, ____________ and __________ are more common.
 

Streptococcus pneumoniae and Listeria monocytogenes

14

Among adolescents and in young adults,_________- is the most common pathogen,
with clusters of cases causing frequent public health concerns. 

 Neisseria meningitidis

15

The introduction of immunization
against Haemophilus influenzae has markedly reduced the incidence of meningitis associated
with this organism in the developed world; the population that was previously at highest risk
(infants) now has a much lower overall risk of meningitis, with _____________ being the most
prevalent organism.

S. pneumoniae

16

Affected individuals typically show__________superimposed on clinical evidence
of meningeal irritation and neurologic impairment, including headache, photophobia, irritability,
clouding of consciousness, and neck stiffness.
 

 systemic signs of infection 

17

A spinal tap yields___________, under increased pressure, with as many as_______________, an
___________ protein concentration, and a __________ glucose content.

 

  •  cloudy or frankly purulent CSF
  •  90,000 neutrophils per cubic millimeter
  • increased
  • markedly reduced

18

Bacteria may be
seen on a smear or can be cultured, sometimes a few hours before the neutrophils appear.
Untreated pyogenic meningitis can be fatal, while effective antimicrobial agents markedly
reduce mortality. 

19

The Waterhouse-Friderichsen syndrome results from ______________(
Chapter 24 .

meningitis-associated
septicemia with hemorrhagic infarction of the adrenal glands and cutaneous petechiae 

20

The Waterhouse-Friderichsen syndrome . It occurs most often with__________ and ____________

 meningococcal and pneumococcal meningitis.

21

The normally clear CSF  is __________and sometimes frankly _____________ in Acute Pyogenic ( Bacterial) Meningitis. 

cloudy

 purulent

22

In acute
meningitis, an exudate is evident within the____________

The meningeal vessels are engorged and stand out prominently.

 

 leptomeninges over the surface of the brain 

23

The location
of the exudate varies; in H. influenzae meningitis, for example, it is usually_________ 

 basal,

 

Mnemonics: HB-- High blood!

24

Whereas in
pneumococcal meningitis it is often densest over the cerebral convexities near the______

 sagittal
sinus. 

25

From the areas of greatest accumulation, tracts of pus can be followed along blood
vessels on the surface of the brain
.

What happens when the meningitis is fulminant, the inflammation may
_______________

extend to the ventricles, producing ventriculitis.

26

On microscopic examination, neutrophils fill  predominantly around the_______________ in less severe
cases

 leptomeningeal blood vessels

27

 

 

On microscopic examination, neutrophils fill the_____________in severely affected
areas 

 subarachnoid space 

28

_______________ may follow pyogenic meningitis and cause hydrocephalus.

Leptomeningeal fibrosis

29

What is chronic adhesive arachnoiditis.?

 In some
infections, particularly in pneumococcal meningitis, large quantities of the capsular
polysaccharide of the organism produce a particularly gelatinous exudate that encourages
arachnoid fibrosis

30

What is Aseptic meningitis?

It  is a clinical term referring to the absence of recognizable organisms in a
patient with meningeal irritation, fever, and alterations of consciousness of relatively acute onset.

The name is a misnomer, as the disease is generally of viral, and rarely of bacterial or
other, etiology. 

31

What is the clinical course of acute aseptic meningitis?

  • It is less fulminant than that of pyogenic meningitis, and
  • the CSF findings also differ;
    • in aseptic meningitis there is a lymphocytic pleocytosis,
    • the protein elevation is only moderate,
    • and the glucose content is nearly always normal.
  • The viral aseptic meningitides are usually self-limiting and are treated symptomatically.
  • Remarkably, even with molecular methods for detection of pathogens, the etiologic agent is identified in only a minority of cases. [19]

 

32

In acute aseptic meningitis, the spectrum of pathogens varies seasonally and geographically.

 

33

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).

In these
cases the CSF characteristic is: 

  •  CSF is sterile,
  • there is pleocytosis with neutrophils
  • and an increased protein concentration,
  • but the sugar content is usually normal.

34