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Z MD1 neurology > CNS Infection > Flashcards

CNS Infection Flashcards

1
Q

what age group is most likely to get meningitis

A

young children

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2
Q

if someone was to get meningitis, who are the most likely to die from it

A

the elderly

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3
Q

what is aseptic meningitis

A

bacterial meningitis that is culture negative + and meningitis caused by things other than bacteria

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4
Q

what are the three bacteria that are the commonest causes of meningitis and what is THE most common

A

H. influenza N. Meningitidis - most common S. pneumoniae

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5
Q

Which type of meningitis is the most prevalent throughout the world

A

A

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6
Q

why do certain bacteria over others tend to cause meningitis

A

because they are encapsulated and therefore can avoid complement fixation and phagocytosis by the immune system

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7
Q

which additional bacteria are neonates exposed to that can cause meningitis

A

E coli and other gram negatives (group B strep and Listeria)

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8
Q

what is the likely source of the bacteria causing menigitis

A

commensals of the nasopharynx

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9
Q

what is the typical clinical presentation of an child/adult with meningitis

A

fever, vomiting/nausea, headache, stiff neck, photophobia, seizures

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10
Q

what is the typical clinical presentation of a baby with meningitis

A

fever, nausea/vomiting, irritable, refusing to feed, altered mental state, bulging fontanelle

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11
Q

when do you get the non-blanching rash associated with meningitis

A

when you have meningococcal septicaemia

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12
Q

what is the defining sign for meningitis

A

abnormal CSF

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13
Q

what are the differences between CSF in viral and bacterial meningitis

A

viral - 100s of LYMPHOCYTES, with negative grain stain, lower amount of protein and higher glucose bacterial - 1000s of NEUTROPHILS, with gram stain positive, higher protein and lower glucose

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14
Q

major contraindications for lumbar puncture

A

raised ICP shock extensive purpura convolutions coagulation abnormalities

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15
Q

why is it important for CSF analysis to occur quickly after the sample has been taken

A

because the WBCs start to lyse as they are in hypotonic solution

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16
Q

what is the empiric antibiotic treatment for meningitis in infants, children and adults

A

intravenous 3rd generation cephalosporin

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17
Q

what is the empiric antibiotic treatment for meningitis in neonates

A

E coli and other gram negatives - 3rd generation cephalosporin group B streptococcus and Listeria = intravenous penicillin and gentomycin

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18
Q

what is the most common sequalae of bacterial meningitis

A

hearing loss

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19
Q

what is the most common cause of encephalitis

A

viral: HSV

20
Q

what is the fundamental difference in the clinical presentation of meningitis and encephalitis

A

encephalitis - you have altered conscious state

21
Q

what are the normal values of CSF

A

pressure less than 150mmH20 protein less than 0.4g/l WBC less than 5x10^6 no RBC gram stain negative glucose more than 60% blood

22
Q

difference between neurotropic and neuroinvasive virus

A

neurotropic - able to replicate in nerve cells neuroinvasive - capable of entering or infecting the CNS

23
Q

main causes of viral encephalitis

A

HSV 1 and 2 rabies virus arboviruses enteroviruses

24
Q

what do we think postinfectious encephalomyelitis is caused buy

A

autoimmunity - parts of the virus look like parts of the myelin sheath of nerves and therefore the immune system starts to degrade myelin sheath of nerves after a viral infection

25
Q

common viruses that cause Guillain-Barré syndrome

A

EBV CMV HIV

26
Q

What is Reye’s syndrome

A

post-infectious influenza or chickenpox causing cerebral edema but no inflammation

27
Q

what are the ways in which viruses can enter the CNS

A
  • by entering peripheral nerves/ganglia and then travelling via axon fibres up to the CNS - via the blood (meningeal BVs, cerebral BVs, coroplexus) - via the olfactory bulb
28
Q

how are viruses protected when replicating in neurons

A

they are protected by attack from Cytotoxic T cells as neurons do not express MHC class 1 molecule

29
Q

where does the viral replication actually occur in the PNS/CNS

A

in the cell body of the neuron

30
Q

which viruses can enter the CNS via the olfactory bulb

A

coronavirus HSV

31
Q

which viruses can enter the CNS via the blood stream

A

poliovirus, mumps, measles, coxsackievirus, HIV in monocytes

32
Q

which viruses can enter the CNS via peripheral nerves

A

rabies yellow fever HSV 1 and 2

33
Q

describe the structure of the rabies virus

A

bullet shaped -ve stranded RNA - helical capsid - envelope

34
Q

how does rabies virus cause neuronal damage

A

replication of the virus involves glycoproteins being displayed on the cell surface (for budding) –> immune system recognises these and destroys the cell

35
Q

mechanism of rabies pathogenesis

A

rabid animal bites you –> virus from the saliva gets into the myocytes at the bite wound and eventually find the peripheral nerve innervating the muscle –> up the spinal cord –> brain –> salivary glands

36
Q

signs of rabies infection

A

aggression thirst

37
Q

what is the one special thing about rabies virus

A

it is the only virus that you can vaccinate for after infection (up to 12 days)

38
Q

explain the neuroinvasiveness and neurovirulence of: - rabies virus - HSV 1 - poliovirus

A

rabies - both high HSV 1 - low neuroinvasiveness and high neurovirulence poliovirus - low neuroinvasiveness and high neurovirulence

39
Q

explain the structure of HSV 1

A

linear dsDNA genome icosahedral envelope

40
Q

explain the pathogenesis of HSV 1

A

primary infection of the mucosal surface –> latent phase –> reactivated

41
Q

how can HSV cause encephalomyelitis

A

if when reactivated from the latent stage it enters the blood –> replicated up in the liver and spleen –> spinal cord –> CNS Or when reactivated from the latent stage is migrates the wrong way and migrates straight into the spinal cord (most common)

42
Q

what is the structure of the HSV1 virus when it is latent in the body

A

maintained as an episome coated with histones

43
Q

structure of poliovirus

A

+Ve stranded RNA virus icosahedral capsid no envelope

44
Q

how does poliovirus cause CNS effects

A

ingested replicates in gut associated lymphoid tissue enters regional lymph nodes enters blood enters BBB enters spinal cord (replicates in the anterior horn cells causing cell destruction and paralysis)

45
Q

which enteroviruses can cause enterovirus meningitis

A

all coxsackie B types coxsackie A7 coxsackie A9 many echoviruses

Z MD1 neurology (17 decks)

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