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3C week 3 - headaches and tingly toes > CNS infections > Flashcards

CNS infections Flashcards

1
Q

what is the CNS impermable to

A

large molecules

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2
Q

what is the main route of invasion for pathogens into the CNS

A

blood vessels

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3
Q

what 2 barriers protect theCNS against pathogen invasion

A

blood-brain barrier; blood-CSF barrier

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4
Q

how can pathogens traverse the protective barriers of the brain (3)

A
  1. growing across - infecting the cells that comprise the barrier;
  2. being passively transported across in intracellular vacuoles;
  3. being carried across by infected white blood cells
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4
Q

blood brain barrier structure

A
  1. thick basement membrane;
  2. astrocyte footplates;
  3. endothelium (no fenstrations)
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5
Q

what produces CSF

A

choroid plexus

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5
Q

blood CSF barrier structure

A
  1. endothelium (fenstrated);
  2. basement membrane;
  3. choroid plexus epithelium
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6
Q

what is the most common route of invasion to the brain (+ examples)

A

blood-borne e.g. polioviruses, neisseria meningitidis

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7
Q

osteomyelitis of the masteoid can lead to what condition

A

meningitis

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8
Q

examples of organisms that invade from peripheral nerves (3)

A

herpes simples; varicella zoster; rabies

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9
Q

what might a high opening pressure in a lumbar puncture indicate

A

inflammation in the brain (CSF under high pressure)

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10
Q

normal CSF charcteristics (3)

A
  1. clear and colourless;
  2. viscosity equal to water;
  3. acellular (up to 5 RBC and 5 WBCs are normal but more is abnormal)
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11
Q

when is a clot seen in lumbar puncture

A

in a traumatic tap (not SAH)

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12
Q

what does viscous CSF indicate

A

increased protein content

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13
Q

should antibodies be present in CSF

A

no

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14
Q

2 further investigations if CSF microscopy and cultures come back negative

A

PCR, serology

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14
Q

low CSF glucose level is indicative of what, and why

A

indicates the presence of bacteria as they feed on glucose

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15
Q

what is an important virulence factor in bacterial meningitis

A

polysaccharide capsules

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16
Q

what organisms most commonly cause bacterial meningitis in those <1mo (4)

A
  1. group B strep;
  2. E.coli;
  3. Listeria moncytogenes;
  4. aerobic gram -ve bacteria
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17
Q

what organisms most commonly cause bacterial meningitis in those 1-23mo (5)

A
  1. group B strep;
  2. E.coli;
  3. H.influenzae;
  4. streptococcus pneumoniae;
  5. neisseria meningitidis
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18
Q

what organisms most commonly cause bacterial meningitis in those 2-50yro (2)

A
  1. S. Pneumoniae;
  2. N. meningitidis
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19
Q

what organisms most commonly cause bacterial meningitis in those 50+ (4)

A
  1. S. Pneumoniae;
  2. N. meningitidis;
  3. L. monocytogenes;
  4. aerobic gram -ve bacteria
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20
Q

what organisms most commonly cause bacterial meningitis in those with head trauma (3)

A
  1. s. aureus;
  2. aerobic gram -ve bacteria;
  3. P. acnes;
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21
Q

what special feature allows for its specialised virulence mechanism and also dictates the serotype

A

an antigenic polysaccharide capsule

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22
Q

8 clinical features of a meningococcal meningitis

A
  1. haemorrhagic skin rash;
  2. sudden onset sore throat;
  3. sudden onset headache;
  4. sudden onset drowsiness;
  5. fever;
  6. irritability;
  7. neck stiffness;
  8. photophobia
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23
Q

neisseria meningitidis onset and who it affects

A

acute onset (6-24hrs); presents with a skin rash in children and adolescents

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24
Q

haemophilus influenzae onset and who it affects

A

less acute onset (1- 2 days); affects children <5yrs

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25
Q

streptococcus pneumoniae meningitis onset and who it affects

A

acute onset that may follow pneumonia or septicaemia (in elderly); affects children <2yrs and the elderly

26
Q

what CSF test can be ueeful in determining a bacterial infection

A

serum glucose : CSF glucose ratio (low) - as bacteria breakdown glucose

27
Q

why might antibody testing not be a useful test for meingitis

A

the infection is too acute for an antibody response to be detectable

28
Q

Mgx of acute meningitis (6)

A
  1. alert the lab that a CSF sample is arriving;
  2. start antibiotic + antiviral + antifungal;
  3. isolate
  4. narrow down the medical management when results from the lab have arrived;
  5. steroids (if pneumococcus);
  6. contact tracing - give one off dose of prophylactic Abx to close contacts
29
Q

when are the MenB vaccines given (3)

A

2 months; 4 months; 12 months

30
Q

when is the MenACWY vaccine given

A

14 yrs

31
Q

prior to infecting the CNS, where must S.pneumoniae colonise first

A

nasopharyns mucus; mucosal epithelium

32
Q

how does S.pneuomniae enter the CSF

A

through white cells or vacuoles

33
Q

what meningitis causing organism is the most deadly

A

pneumococcal

34
Q

what histopathological changes can be seen in meningitis (4)

A

haemorrhages; neutrophilic degeneration; abscess formation; infarctions

35
Q

what is the most common type of meningitis

A

viral

36
Q

viral meningitis presentation (4)

A

headache; fever; photophobia; reduced neck stiffness (compared to bacterial)

37
Q

vrial meningitis CSF macro/microscopy

A

macro - clear
mirco - cells are mainly lymphocytes (although polymorphonucler leukocytes may be dominant in early phases)

38
Q

what commonly causes encephalitis

A

viruses

39
Q

how does the meninges appear in a CT scan of encephalitis

A

not inflamed

40
Q

infectious differentials for encephalitis (types)

A
  1. viral (herpes simplex, measles, mumps etc.);
  2. bacterial (neisseria meningitidis, H.influenzae etc.);
  3. parasitic (malaria etc.);
  4. fungal (cryptococcal);
  5. para/post infectious (acute disseminated encephalomyelitis)
41
Q

5 non-infectious differentials for encephalitis

A
  1. vascular (SAH,SDH etc.);
  2. neoplastic/ paraneoplastic;
  3. metabolic (renal encephalopathy, toxins etc.);
  4. epilepsy;
  5. antibody mediated encephalitis
42
Q

infection of blood vessels –> infection of CNS cells pathway

A

virus/infected leukocyte localises in blood vessels –> pathogen leaves blood vessels –> sensitised T cells release cytokines –> cytokines induce infiltration of mononuclear cells –> infection of neural cells –> further spread and destruction of infected neural cell

43
Q

3 causes of recurrent bacterial meningitis

A
  1. basal skull defects;
  2. recurrent aseptic meningitis (usually HSV2 and hx of recurrent genital lesions);
  3. congenital dermal sinus
44
Q

what causes brain abcesses

A

infection with bacteria or fungi

45
Q

examples bacterial spread from nearby tissue infection causing brain abcesses (3)

A
  1. persistant middle ear infection;
  2. sinusitis;
  3. mastoiditis (infection of bone behind the eye)
46
Q

3 ways bacteria can spread to cause brain abcesses

A
  1. via neraby tissue infection;
  2. haematogenous spread;
  3. neurosurgical inoculation
47
Q

3 main microorganisms responsible for brain abscess formations

A
  1. streptococcus pneumoniae, H.influenzae or candidia from nearby ENT infection;
  2. Staphylococcus species via iatrogenic infection;
  3. any other microorganism via haematogenous spread
48
Q

examples of fungal causes of brain abscesses

A

aspergillus; candida; cryptococcus; mucorales

49
Q

examples of protazoal causes of brain abcesses

A

toxoplasma gondii; entamoeba histolytica; paragonimus

50
Q

what can aid in the diagnosis of toxoplasmosis

A

serological tests

51
Q

what common conditions increases the risk of brain abscesses

A

diabetes

52
Q

brain abscess Mgx

A
  1. surgical excision/drainage;
  2. prolonged antimicrobial therapy (4-8 weeks)
53
Q

why is it essential to chose the correct antobiotics for CNS infections

A

antibiotics are generally large molecules which cannot cross the BBB - only specific ones can cross and actually enter the the CNS

54
Q

what is the most critical factor in survival for bacterial menigitis

A

door-to-antibiotics time

55
Q

what abx should be given if presenting out of hospital w a purpuric rash

A

ceftriaxone 1g (if >12yrs);

otherwise give benzyl penicillin

56
Q

encephalitis presentation

A

fever, headaches, focal neurological deficits, seizures, and altered or decreased level of consciousness

57
Q

meningitis neck stiffness (rather than ddx neck stiffness)

A

front-back neck stiffness rather than rotational

58
Q

lumbar puncture contraindications (9)

A
  1. raised ICP
  2. focal neurological defecits
  3. dilated/poorly reactive pupil (CN III palsy)
  4. coma/deteriorating conciousness
  5. signs of posterior fossa lesion (dysarthria, ataxia)
  6. local sepsis
  7. coagulopathy
  8. seizures
  9. immunocompimised`
59
Q

when is lumbar puncture the test of choice

A

progressive headache over several days, photophobia, awake +talking

60
Q

3 things that increase the risk of meningitis

A
  1. pneumonia
  2. otis media
  3. alcohol
61
Q

why do you not have to treat viral meningitis

A

virus doesn’t spread to brain, just remains on meninges

62
Q

TB meningitis presentation

A
  1. subacute/chronic onset;
  2. mild headache;
  3. low grade grumbling fever;
  4. CN palsies
63
Q

which lobes are greatly affected in encephalitis

A

temporal lobes

64
Q

encephalitis treatment

A
  1. IV FLUIDS
  2. anti-inflammatory meds (steroids etc.)
  3. anti-convulsatns (phenytoin)
  4. acylovir (or other to treat underlying cause)
65
Q
A

3C week 3 - headaches and tingly toes (7 decks)

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