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PATHOLOGY > CNS infections > Flashcards

CNS infections Flashcards

1
Q

what are the 4 routes of entry of CNS infections

A

Haematogenous

Direct implantation - via instruments

Local extension - secondary to established infections

PNS into CNS - virus

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2
Q

signs and sx of meningitis

A

fever

headache

stiff neck

some disturbance of brain function

vomiting

light aversion

drowsy

joint pain

fitting

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3
Q

agents that cause meningitis

A

neisseria meningitidis

streptococcus pneumoniae

Haemophilus influenzae

TB

various viruses

cryptococcus neoformans

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4
Q

pathophysiology of meningitis

A

Neuro damage by:

  • Direct bacterial toxicity - meningococcus in menignes -> infection
  • Indirect inflammatory process and cytokine release and oedema
  • Seizure, shock, and cerebral hypoperfusion
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5
Q

px of meningits

A

10% mortality

5% morbidity of survivors - neuro sequelae mainly sensineural deafness

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6
Q

signs and sx of encephalitis

A

disturbance of brain function

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7
Q

agents that cause encephalitis

A

rabies virus

arbovirus

trypanosoma species

prions

amoeba

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8
Q

signs and sx of myelities (affects spinal cord)

A

disturbance of nerve transmission

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9
Q

agent that causes myelitis

A

poliovirus

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10
Q

signs and sx of neurotoxin (affects CNS and PNS)

A

paralysis

rigid - tetanus

or flaccid - botulism

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11
Q

agents that cause neurotoxin

A

clostridium tetani

clostridium botulinum

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12
Q

what is meningitis

A

inflammatory process of
meninges and CSF

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13
Q

what is meningencephalitis

A

inflammation of meninges and
brain parenchyma

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14
Q

causes of acute meningitis in order of liklihood

A

Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
Listeria monocytogenes - old, poor immune system
GBS - colonise vagina, can go through microabrasions in baby head -> meningitis
E coli - vaginas -> neonatal sepsis

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15
Q

summarise neisseria meningitides

A

Infectious cause of childhood death in all countries.

Transmission is person-to-person, from asymptomatic carriers.

non-blanching rash in 80%

stains - A B C Y W135 - vaccines for all

1/2 present just as meningits
1/2 have some degree of septicaemia

Pathogenic strains are found in only 1% of carriers.

Cause infections in less than 10 days.

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16
Q

how can we reduce N meningitidis transmission

A

stop travel and contact

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17
Q

why is it important to differentiate between meningitis and septicaemia

A

patients who present with shock are treated differently than patients who present primarily with increased intracranial pressure (ICP).

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18
Q

pathophysiology of septicaemia

A

capillary leak:
* albumin and other plasma proteins -> hypovolaemia

coagulopathy -> bleeding and thrombosis
* Endothelial injury results in platelet-release reactions
* The protein C pathway.
* Plasma anticoagulants.
* no LP - because will clot - important to look at bloods before LP!!

metabolic derangement - esp acidosis

myocardial failure - multiorgan failure

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19
Q
A

severe meningococcal disease and purpura fulminans

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20
Q
A

meningococcal septicaemia

Amputation or skin grafting due to digital or limb ischemia is required in 2-5% of survivors

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21
Q

features of chronic TB meningitis

A

indolent
Week long presentation
Not associated with rash

more common immunocomp

involves meninges and basal cisterns of brain and spinal cord

Can become TB abscess/granulomas or cerebritis in brain

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22
Q

epidemiology of aseptic meningitis

A

most common infection of CNS

mostly children less than 1yr

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23
Q

sx of aseptic meningitis

A

headache

stiff neck

photophobia

nonspecific rash

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24
Q

causes of aseptic meningitis

A

by definition - absence of bacteria

Enteroviruses (e.g. Coxsackievirus group B and echoviruses) are responsible for 80-90% cases

herpes can spread haemtologically to meningitis

25
Q

clinical course of aseptic meningitis

A

self-limited and resolves in 1-2 weeks.

25
Q

viral causes of encephalitis

A

enterovirus
herpes
VZV

26
Q

non-viral causes of encephalitis

A

Bacterial encephalitis - Listeria monocytogenes -worse mortality and morbidity than listeria meningitis

toxoplasmosis

Amoebic encephalitis

  • Naegleria fowleri fatal - Habitat: warm water
  • Acanthamoeba species, and Balamuthia mandrillaris,
    -> brain abscess, aseptic or chronic meningitis.
27
Q

summarise toxoplasmosis as a cause of encephalitis

A

obligate intracellular protozoal parasite, Toxoplasma gondii.

Via the oral, transplacental route or organ transplantation.

Severe infection in immunocompromised patients. -> brain parenchyma -> encephalitis

Affected organs include the gray and
white matter of the brain, retinas,
alveolar lining of the lungs, heart, and skeletal muscle.

28
Q

what are the most fatal encephalitis(es)

A

virus and parasites are much worse than bacteria

29
Q

transmission of viral meningitis

A

mosquitoes

lice

tics

person to person

30
Q

what is becoming the leading cause of encephalitis internationally

A

west nile virus

31
Q
A

brain abscess

32
Q

pathophysiology of brain abscess

A

Usually from direct extension mode of infection - ear, or mastoid process, or sinuses

otitis media/mastoiditis/paranasal sinuses endocarditis/haematogenously

Therefore it’s the bugs that cause ear, mastoid or sinus infections

33
Q

microbes that cause brain abscesses

A

Streptococci (both aerobic and anaerobic)

Staphylococci,

Gram-negative organisms. (particularly in
neonates)

Mycobacterium tuberculosis

fungi

parasites

Actinomyces and Nocardia species

34
Q

summarise spinal infections

A

Pyogenic vertebral osteomyelitis common form of vertebral infection.

transmission:
* Direct open spinal trauma,
* infections in adjacent structures,
* hematogenous spread of bacteria to a vertebra. - IVDU staph aureus septicaemia spread to spine

Px - Left untreated, it can lead to:
* permanent neurologic deficits,
* significant spinal deformity,
* death.

Finate space around spine - so even small abscess have bad sequaelae

35
Q

RF for spinal infections

A

Advanced age

Intravenous drug use

Long-term systemic steroids

Diabetes mellitus

Organ transplantation

Malnutrition

Cancer

36
Q

Ix for CNS infections

A

MRI
(CT cant see meninges - just if SOL in parenchyma)

CSF

biopsy

blood culture

throat swab
* strep pneumoniae - 1 in 5 carry in nasopharynx
* meningococcus - 1 in 20 carry in nasopharynx

37
Q

what do you comment on in CSF studies

A

Color/Clarity

Cell counts

Chemistry
* (Protein/ Glucose)

Stains
* (Gram/ Auramine(ZN)/ India Ink)

Cultures
* (bacterial, fungal, TB)

PCR

38
Q

how many white cells in CSF is normal

A

less than 5

39
Q

what does neutrophils in CSF mean

A

bacteria

40
Q

what does lymphocytes (PMN) in CSF mean

A

viral

41
Q

what is india A stain for

A

cryptococcus

42
Q

main differentials for these:

A
43
Q
A

gram +ve cocci - pneumococcus

44
Q
A

Gram negative cocci- meningococcus

45
Q
A

Gram positive rod- Listeria

46
Q
A

Ziehl-Neelsen stain- TB

47
Q
A

cryptococcus

48
Q

Limitations of diagnostics for CNS infections

A

MRI oedema pattern and moderate mass effect cannot be differentiated from tumor or stroke or vasculitis in some patients.

Infections in early stages and serological tests.

Amount of CSF.

PCR techniques.

Methods to detect amoebic infections.

Availability of good laboratory technique.

49
Q

time frame for investigations for CNS infection

A
50
Q

Mx of meningitis - need to know dose

A

Ceftriaxone 2g iv bd

If >50yrs or immunocompromised add:
Amoxicillin 2g iv 4hourly - cover listeria

51
Q

mx for meningoencephalitis - need to know dose

A

Aciclovir 10mg/kg iv tds

Ceftriaxone 2g iv bd

If >50yrs or immunocompromised add:
Amoxicillin 2g iv 4hourly

52
Q

mx s pneumoniae

A

Pen G 18-24 mu/d or

Amoxicillin 12 g/d or

Ceftriaxone 4 g/d or

Chloro 75-100 mg/kg/d

53
Q

mx n meningitides

A

Pen G 18-24 mu/d or

Amoxicillin 12 g/d or

Ceftriaxone 4 g/d or

Chloro 75-100 mg/kg/d

54
Q

mx H influenzae

A

Cefotaxime 12 g/d or Ceftriaxone 4 g/d

55
Q

mx GBS

A

Pen G or Amoxicillin
[plus aminoglycoside]

56
Q

mx listeria

A

Amoxicillin 12 g/d
plus aminoglycoside

57
Q

mx gram -ve bacilli

A

Cefotaxime 12 g/d or Ceftriaxone 4g/d

58
Q

mx pseudomonas

A

Meropenem 6g/d or Ceftazidime 6g/d

PATHOLOGY (94 decks)

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