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defence > Meningitis > Flashcards

Meningitis Flashcards

1
Q

what is the most common route of microbial entry into the CNS

A

1)via the blood

can also enter via:

2) direct implantation,
3) local spread from other infections,
4) from the PNS

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2
Q

which two routes can microbes enter the CNS via the blood

A

capillaries within the brain parenchyma –> encephalitis or brain abscesses

the choroid plexus –> meningitis

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3
Q

what features of the brain microvascular endothelian cells makes crossing of pathogens more difficult in the brain parenchyma

A

tight junctions have strong electrical resistance and therefore there is REDUCED PARACELLULAR FLUX

BMEC also has an extra slow rate of fluid-phase endocytosis therefore there is REDUCED TRANSCELLULAR FLUX

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4
Q

what facilitates/inhibits the crossing of pathogens at the choroid plexus

A

1) fenestrated endothelium –> INCREASED PERMEABILITY
2) epithelium has fast rate of endocytosis –> INCREASED TRANSCELLULAR FLUX
3) weaker tight junctions and weaker electrical resistance –> INCREASED PARACELLULAR FLUX

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5
Q

which bacteria meningitis is associated with a haemorrhagic skin rash

A

Neisseria meningitidis

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6
Q

during which season is enterovirus meningitis more common

A

in the summer

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7
Q

which time of the year do epidemics of meningococcal meningitis tend to occur

A

the first quarter of the year

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8
Q

which organism do meningitis C vaccines protect against

A

neisseria meningitidis

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9
Q

describe the structure of neisseria meningitidis bacteria

A

gram-negative diplococcus

capsulated

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10
Q

which group of meningococcus causes the highest frequency of CNS infection

A

Group B

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11
Q

describe the structure of streptococcus pneumoniae

A

gram-positive capsulated coccus

naturally present in the throat

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12
Q

what is the pathogenesis of streptococcus pneumoniae

A

RT (pneumonia) -> blood (bacteraemia) –> meninges

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13
Q

which streptococcus pneumoniae vaccine is given to the <2s

A

PCV 13 which protects against 13 meningitis causing serotypes

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14
Q

which streptococcus pneumoniae vaccine is given to the >65s

A

PPV which protects against 23 pneumonia causing serotypes

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15
Q

which infections do non-invasive streptococcus pneumoniae cause

A

otitis media
sinusitis
bronchitis

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16
Q

describe the structure of Haemophilus influenzae

A

gram-negative coccobacillus naturally present in the throat

present both as capsular and uncapsular - capsulated type b capable of causing meningitis in young children

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17
Q

which infections can capsulated strains of H. influenzae cause

A

meningitis
epiglottitis
pneumonia
bacteraemia

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18
Q

how does mycobacterium tuberculosis present

A

gradual onset

infection focus usually elsewhere (usually the lungs)

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19
Q

in which age group is TB meningitis most common in areas where TB prevalence is high

A

children < 5

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20
Q

in which age group is TB meningitis most common in areas where TB prevalence is low

A

adults

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21
Q

how do fungal meningitis present

A

gradually

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22
Q

which type of fungus causes the most cases of fungal meningitis

A

cryptococcus neoformans

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23
Q

wht condition can cause a pure encephalitis which infects the brain via the PNS

A

RAbies

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24
Q

which is the most common cause of encephalitis in the UK

A

HSV type 1
characterised by extensive and asymmetric necrosis of the temporal lobes
neonates can acquire primary infection as pass through birth canal!

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25
Q

complications of bacterial meningitis

A 
sepsis -> shock -> death
cerebral oedema (raised ICP)
cerebral thrombophlebitis
permanent neurological complications
cerebral abscess
subdural empyema
leptomeningeal fibrosis (ostructive hydrocephalus)
epilepsy
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26
Q

what may be evident on TB meningitis pathology

A

thick basal exudate
granulomas with caseation
arachnoid fibrosis
tuberculomas

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27
Q

what is tabes doralis

A

syphilitic myelopathy - slow demyelination resulting in:

  • lightning pains
  • ataxia and stamping gait
  • neuropathic joints
  • Argyll Robertson pupils
  • ptosis and optic atrophy

secondary to syphilis infection

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28
Q

shingles can cause encephalitis, how?

A

reactivation of the varicella zoster virus following primary infection of chicken pox

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29
Q

which are the most common intra-uterine CNS infections

A

CMV
Rubella
Toxoplasmosis

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30
Q

in which period of pregnancy is the highest risk from CMV

A

2nd trimester
causes necrotising encephalitis
this results in mental retardation, microcephaly and deafness

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31
Q

in which period of pregnancy is the risk of malformation greatest from rubella

A

the first - decreases as pregnancy continues

causes heart defects, cataracts, deafness and mental retardation

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32
Q

in which period of pregnancy is toxoplamosis most dangerous

A

1st trimester: abortion/stillbirth

2nd: severe brain and organ damage
3rd: moderate cerebral damage, chorioretinitis

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33
Q

what is acute disseminated encephalomyelitis

A

rare sequel to viral infections
presents as:
fever, headache, vomiting, drowsiness, coma, focal neurology, widespread patchy demyelination and perivascular inflammation

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34
Q

what is acute haemorrhagic leukoencephalitis

A

a more severe form of acute disseminated encephalomyelitis

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35
Q

what is subacute sclerosing panencephalitis

A

rare late sequel of measles

presents as mental deterioration, fits, myoclonus and pyramidal signs

36
Q

what are the clinical features of Creutzfeld-JAcob disease

A

rapidly progressive dementia
ataxia
myoclonus
psychiatric features (new variant)

37
Q

what would be seen on pathology in Creutzfeld-Jacob disease

A 
spongiform change
amyloid PrP rich plaques
neuronal loss
gliosis
atrophy
38
Q

in which age group is the highest incidence of meningitis

A

<2 months

80.69 per 100,000 population

39
Q

which organism is the most common cause of bacterial meningitis in the first month of life

A

group B strep
e coli
listeria

40
Q

which organism is the most common cause of bacterial meningitis in 1 month - 3 months

A

group B strep
gram ive
s pneumoniae
n meningitis

41
Q

which organism is the most common cause of bacterial meningitis in 3 months - 3 years

A

s pneum
n mening
group B strep
gram -ve

42
Q

which organism is the most common cause of bacterial meningitis 10yrs-19yrs

A

n mening

43
Q

list 3 risk factors to meningitis

A 
>60 or <5
DM
renal/adrenal insuff
CF
HIV
splenectomy
sickle cell disease
ALCOHOLICS!
crowing
recent exposure
dural defect
Thalassaemia major
IV drug use
bacterial endocarditis
VP shunt
malignancy
44
Q

what are the two patterns of presentation of acute bacterial meningitis

A

progressive (preceded by febrile illness)

acute and fulminant (develops rapidly, signs of sepsis, associated with severe brain oedema)

45
Q

what is Cushing’s triad

A

late sign of raised ICP

  • systemic hypertension
  • bradycardia
  • respiratory depression
46
Q

what are the signs and symptoms of bacterial meningitis in neonatal - 3 months

A 
maternal infection or pyrexia at delivery
hyper/hypothermia
change in sleeping or eating habits
irritability/lethargy
high pitched cry
seizures
bulging fontanelle
paradoxical irritability
47
Q

how does nuchal rigidity manifest

A 
inability to place chin on chest
limited passive neck flexion
Kernig sign ( cannot extend knee)
Brudzinski signs ( flexes lower extremities during attempted passive flexion)
48
Q

under what circumstances must you do a brain CT before performing an LP

A 
suspicion of raised ICP (papilloedema, raised BP/low HR)
focal neurology
abnormal level of consciousness
seizure within 1 week of presentatino
known CNS lesions
immunocomprimise
>60 years
49
Q

which CT findings are absolute contraindications to LP

A 
midline shift
loss of suprachiasmatic and basilar cisterns
posterior fossa mass
loss of superior cerebellar cistern
loss of quadrigeminal plate cistern
raised ICP
50
Q

which two conditions are relative contraindications to LP

A

coagulopathy
brain abscess

infected skin at needle entry is an absolute contraindication

51
Q

which antibiotics should be used for neonates in the treatment of meningitis

A

ampicillin and cefotaxime or aminoglycoside

52
Q

which antibiotic should be used for the first line treatment of meningitis

A

cephalosporin: cefotaxime or ceftriaxone

chloramphenicol can be used if allergies

53
Q

which childhood immunizations can protect against meningitis

A

Hib
Men C
Strept pneumoniae
MMR

54
Q

what is the mortality rate for neonates in meningitis

A

15-25%

55
Q

what must be treated in order to improve outcome in meningococcaemia

A

hypovolaemia
hypotension
acidosis
respiratory impairment

56
Q

which signs are present in meningitis

A

triad:

  1. headache
  2. neck stiffness
  3. fever

also:

  • photophobia
  • petechial rash
  • vomiting
  • intense malaise
  • rigors
57
Q

what is the gold standard test for confirming bacterial meningitis

A

LP

will be clouding in >90% of pts owing to WCC>100

58
Q

what is the most common complication of strep pneumonia meningitis

A

deafness - all children should have an audiological assessment after meningitis infection

59
Q

what would the CSF look like in viral meningitis

A

clear

increased lymphocytes

60
Q

what would you expect to find on the CSF for bacterial meningitis

A

turbid appearance
raised neutrophils
raised protein
dereased glucose

61
Q

why does strep pneumoniae meningitis have a worse prognosis

A

it produces cytotoxins

62
Q

what would you expect to see on mycobacterial meningitis CSF

A 
clear/mildly turbid appearance
early -> neutrophils then lymphocytes
raised protein
decreased glucose
positive AFB
63
Q

what is the main cuase of encephalitis in the UK

A

herpes simplex

causes extensive asymmetric necrosis of temporal lobes

64
Q

which protozao can cause meningitis

A

malaria

african typanosomiasis

65
Q

what are transmisible spongiform encephalopathies caused by

A

prions

66
Q

how do the bacteria causing meningitis cross the blood brain barrier

A

at the choroid plexus

67
Q

briefly outline the inflammation process in meningitis

A

1) cytokine production - activates pain receptors and leads to meningeal damage
2) increased bloodflow and permeability - oedema and raised ICP
3) immune cell recruitment - increased inflammation and tissue damage

68
Q

what is opistonus

A

hyperextension and spascity of the back

69
Q

what do gram stains on CSF indicate

A

gram +ve -> strep pneumoniae

gram -ve -> n meningitidis

70
Q

name three complications post treatment of meningitis

A

deafness
learning difficulties
cerebral palsy

71
Q

which antibiotics are used as chemoprophylaxis for meningitis

A

ciprofloxacin
rifampicin
ceftriaxone

these are the only 3 abx with an evidence basis

72
Q

who should receive chemoprophylaxis for meningitis

A

transmission of meningococci only likely to occur following prolonged close contact

73
Q

what is the maximum incubation period

A

2-7 days

74
Q

what is the absolute risk of a house hold contact transmitting meningitis

A

1 in 500 within the next month

75
Q

what is the aim of chemoprophylaxis

A

eliminate the carriage of meningococci

reduces the risk by 90%

76
Q

list 3 risks of chemoprophylaxis of meningitis

A

1) increased exposure to abx -> resistance
2) side effects
3) affects commensual organisms - eg neisseria lactamina which has similar surface proteins to nm and therefore aids natural immunity

77
Q

should a child who has been diagnosed with meningitis receive chemoprophylaxis

A

yes! to erradicate carriage unless already treated with ceftriaxone

78
Q

what would you see on the CSF in herpes simplex encephalitis

A

lymphocytosis
mildly raised protein
usually normal glucose
HSV on PCR

79
Q

what are the clinical features of herpes zoster (shingles)

A

blistering rash affecting dermatome
if affects eye (V1) can cause corneal abrasions
Ramsey Hunt syndrome

80
Q

what is the most likely cause of meningitis following skull fracture, ear disease or congenital CNS lesion

A

pneumococcal infection

81
Q

what is the most likely cause of meningitis folowing rash and pleuritic pain

A

enterovirus infection

82
Q

what is the most likely cause of meningitis following working in water and presenting with myalgia, conjuctivitis and jaundice

A

leptospirosis

83
Q

what are the late signs of raise ICP

A 
bulging fontanelle
neck stiffness
opisthotonos
rash
fall in BP
84
Q

what is idiopathic intracranial hypertension, who is it most common in and what is it associated with?

A

CSF pressure> 200 in nonobese (250 in obese)
in young women
associated with obesity

85
Q

what is the difference between communicating and non-communicating (blocked) hydrocephalus

A

communicating - blockage after the ventricles at the cisterns. Often caused by SAH and meningitis

non-communicating - one of the narrow passages connecting the ventricles is blocked

86
Q

what is the triad of clinical symptoms in normal pressure hydrocephalus

A

gait disturbance, dementia and incontinence

defence (12 decks)

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