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A13AMC @ UoN > L15 - Infections of the CNS (Meningitis & Brain Abscess) > Flashcards

L15 - Infections of the CNS (Meningitis & Brain Abscess) Flashcards

1
Q

Define Meningitis

A

Inflammation of the meninges

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2
Q

What are the four possible routes of infection by which meningitis might arise?

A

Blood-borne
Paraminingeal suppuration
Direct spread through dural defect
Direct spread through cribriform plate

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3
Q

Give several examples of the possible complications of meningitis

A 
Death
Subdural collection
Cerebral vein thrombosis
Hydrocephalus
9-15% Deafness (Hib)
Convulsions
Visual/Motor/Sensory deficit
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4
Q

What are the five causative organisms most commonly implicated in meningitis?

A 
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilius influenzae type B
Escherichia coli
Listeria monocytogenes
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5
Q

In what group is N. meningitidis most common?

A

Children

Young adults

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6
Q

In what groups is S. pneumoniae most common?

A

Elderly

Children <2yrs

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7
Q

In what group is H. influenzae type B most common?

A

Children <5yrs

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8
Q

In what group is E. coli most common?

A

Neonates

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9
Q

In what group is L. monocytogenes most common?

A

Neonates

Immunocompromised

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10
Q

Describe the characteristics of normal cerebrospinal fluid

A

Low protein
Low IgG
No lymphatics
BBB so only lipophilic compounds

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11
Q

What bacterial factors act as inflammatory mediators?

A

Endotoxins of Gram-ve bacteria
Lipoteichoic peptidoglycan components of Gram+ve cell walls
TNF, IL-1/6/8, NO, PAF

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12
Q

What immune cells migrate to the CSF following the effect of these inflammatory mediators?

A

Neutrophils

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13
Q

What effect does the migration of neutrophils to the CSF have?

A

Release of proteolytic products (Ox radicals)

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14
Q

What effect do Ox radicals have?

A

They damage the vascular endothelium
Changes BBB permeability
Alters CSF dynamics

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15
Q

Describe the pathogenesis of bacterial meningitis

A

Nasopharynx to
Bloodstream to
Choroid Plexus to
CSF

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16
Q

What is the most common route of infection?

A

Blood-borne from a respiratory site (nasopharynx)

Across the choroid plexus into the subarachnoid space and into the CSF

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17
Q

Which three organisms can easily colonise the nasopharynx and penetrate vascular tight junctions?

A

S. pneumoniae
N. meningitidis
H. influenzae type B

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18
Q

What bacterial factors enable colonisation of the nasopharynx?

A

IgA protease

Pili

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19
Q

What bacterial factors enable bacteraemia?

A

Endocytosis across tight junctions

Capsules to resist lysis/phagocytosis

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20
Q

What factors cause the slow immune response in the subarachnoid space?

A

No Immunoglobulin, C3/C4 or phagocytes

Delayed response

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21
Q

What are the classic symptoms of Meningitis?

A

Global headache
Neck and back stiffness
Nausea/Vomiting
Photophobia (non-specific)

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22
Q

What are the symptoms of Meningitis in infants?

A 
Flaccid/Opisthotonus
Bulging fontanelle (increased ICP)
Fever/Vomiting
Strange cry
Convulsions
Typical signs are often not present <18mo
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23
Q

What common conditions present similarly to Meningitis?

A

Sub-arachnoid haemmorhage
Malignancy
Other infections

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24
Q

What are the physical signs of Meningitis?

A

Fever
Petechial/purpuric rash
Photphobia
Irritation of the motor roots

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25
Q

What physical effect does irritation of the motor roots have?

A

Kernig’s +ve (hamstring spasm)
Neck stiffness
Brudzinskis sign (flexion of neck causes hip/knee flexion)

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26
Q

What is the best diagnostic test in Meningitis?

A

Lumbar puncture

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27
Q

What are the pros/cons of an LP?

A

Pros - Distinguish between bacterial/viral, rapid

Cons - Risk of herniation (longer history, focal neurology, drowsy, decreased clotting)

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28
Q

What are the normal CSF values?

A 
Leukocytes - <5
Polymorphs - x
Lymphoycytes - x
Glucose - 60-80% BG
Protein - 0.1-0.4g
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29
Q

Describe the CSF changes present in Meningitis

A 
Increased leukocytes (B>T>V)
Presence of neutrophils (B>T>V)
Presence of lymphocytes (V>T>B)
Decreased glucose (T>B)
Raised protein (B>T>V)
30
Q

What are the most common possible complications of Meningococcal disease?

A

Death 13% (40% in septicaemia)
Necrotic lesions
Reactive arthrtis (young adults)
Serositis

31
Q

What are rarer complications of Meningococcal disease?

A

Neurological sequelae

Abscess formation

32
Q

What are risk factors for a poor outcome?

A 
Age
Presence of otitis media/sinusitis
Absence of rash
Tachycardia
Low GCS
\+ve Blood culture
Thrombocytopenia
Low CSF leukocyte count
33
Q

How should meningitis be managed?

A 
Antibiotics
Oxygenation
Prevention of hypoglycaemia/hyponatraemia
Anticonvulsants
Decrease ICP
34
Q

What are the ideal antibiotic characteristics for meningitis?

A

Bactericidal
Sufficient penetration into CSF (non-toxic)
Good activity against pathogens
Little endotoxin released on organism death

35
Q

What six factors can increase antibiotic penetration of the BBB?

A 
High lipid solubility
Low molecular weight
Low ionisation
High serum concentration
Low protein binding
Meningeal inflammation
36
Q

Describe the pros of Chloramphenicol for treating Meningitis

A

Good CSF penetration (i.v. and oral)

Active against organisms

37
Q

Describe the cons of Chloramphenicol for treating Meningitis

A

Bacteriostiatic
Resistance in Hib/Pneumococci
Causes aplastic anaemia/Grey baby syndrome

38
Q

How is Chloramphenicol used to treat meningitis?

A

Reserve agent for allergic patients

39
Q

Describe the pros of Ceftoaxime/Ceftriaxone for treating Meningitis

A

Good penetration into inflamed CSF
Active against organisms
Active against penicillin resistant pneumococci AND ampicillin resistant Hib

40
Q

How are Cefotaxime/Ceftriaxone used to treat meningitis?

A

First line treatment in adults AND children
Cefotaxime - 6 hourly
Ceftriaxone - 12 hourly

41
Q

Describe the pros of Benzylpenicillin to treat meningitis

A

Most active agent for penumococcal meningitis

Penetration of inflamed meninges

42
Q

Describe the cons of Benzylpenicillin to treat meningitis

A

Short half life (4 hourly dosing)
High serum levels increase risk of epileptic fits
Increasing incidence of resistance

43
Q

How is Benzylpenicillin used to treat meningitis?

A

Treatment for known sensitive organisms

4 hourly dosing

44
Q

What is the penetration ratio for Chloramphenicol?

A

9:1

45
Q

What is the penetration ratio for Cefotaxime/Ceftriaxone?

A

1:10

46
Q

What is the penetration ratio for Benzylpenicillin?

A

1:23

47
Q

What is the antimicrobial therapy for N. meningitidis?

A

Benzylpenicillin if sensitive

Cefotaxime/Ceftriaxone if not

48
Q

What is the antimicrobial therapy for S. pneumoniae?

A

Benzylpenicillin if sensitive
Cefotaxime/Ceftriaxone if not
Add Vancomycin if strain may be resistant

49
Q

What is the antimicrobial therapy for Hib?

A

Cefotaxime/Ceftriaxone

50
Q

What is the antimicrobial therapy for an unknown organism? - Child >2mo and adults

A

Cefotaxime/Ceftriaxome

Add Amoxicillin if >50 or immunocompromised

51
Q

What is the antimicrobial therapy for an unknown organism? - Child <2mo

A

Benzylpenicillin AND Gentamicin

52
Q

What is the length of treatment for N. meningitidis?

A

7 days

53
Q

What is the length of treatment for S. pneumoniae?

A

14 days

54
Q

What is the length of treatment for Hib?

A

7 days

55
Q

What is the length of treatment for L. monocytogenes?

A

> 21 days

56
Q

What is the length of treatment for unknown organisms?

A

7-14 days i.v. treatment

57
Q

When does giving steroids improve long-term morbidity?

A

Hib meningitis in children

Steroids given prior to antibiotics

58
Q

What three vaccines are available for meningitis?

A

Conjugated Hib and Meningococcal group C Pneumococcal vaccine (<2 yrs)
Men B vaccine
Polyvalent pneumococcal polysaccharide vaccine

59
Q

What chemoprophylaxis is available for meningitis?

A

Rifampicin OR Ciprofloxacin

60
Q

Define a brain abscess

A

An abscess caused by inflammation and collection of infected material from local/remote infectious sources within the brain

61
Q

What are the clinical signs of a Brain abscess?

A 
Focal neurological signs
Raised ICP
Headache (70-95%, short duration)
Fever (variable)
Raised CRP/ESR
62
Q

What are the possible routes of infection for brain abscess causing organisms?

A

Direct spread (venous connections)
Haematogenous spread
Direct implantation

63
Q

What organisms cause brain abscesses?

A 
Streptococcus milleri (60-70%)
Anaerobes (65%)
Enterobacteriaceae (25%)
Staphylococcus aureus (10%)
Polymicrobial (30-60%)
64
Q

Describe the pathophysiology of brain abscesses

A

1-3 days - Cerebritis with central inflammation
4-9 days - Ring of cerebritis surrounding necrotic centre (+/- mass effect)
10-13 days - Capsule formation
14 days - Capsule helps to limit spread

65
Q

What is the surgical treatment for brain abscess treatment?

A

Drainage (Burr-hole under LA/Craniotomy)

Excision (Craniotomy)

66
Q

What is the medical treatment for brain abscess treatment?

A

Extensive antibiotic coverage

67
Q

What antibiotic treatment is best if the source is likely dental/sinus/haematogenous? (brain abscess)

A

Ceftriaxone + Metronidazole

If streptococcal/anaerobic narrow to Benzylpenicillin + Metronidazole

68
Q

What antibiotic treatment is best if the source is likely otogenic? (brain abscess)

A

Ceftazidime + Benzylpenicilin + Metronidazole OR

Meropenem

69
Q

What antibiotic treatment is best for post-operative/post-traumatic treatment? (brain abscess)

A

Vancomycin + Meropenem

70
Q

What is the general structure of antibiotic therapy? (brain abscess)

A

High dose
6-8 wks
3 wks i.v. then oral

71
Q

What possible side effects are associated with the high doses used for treatment? - Brain Abscesses

A

Bone marrow suppression

Antibiotic fever

A13AMC @ UoN (20 decks)

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