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5. CP - Central Nervous System Infections > (25) Viral Meningitis > Flashcards

(25) Viral Meningitis Flashcards

1
Q

What is meningitis?

A

Inflammation of the meninges

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2
Q

What is encephalitis?

A

Inflammation of the brain

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3
Q

What is meningo-encephalitis?

A

Inflammation of the brain and meninges

often difficult clinically to distinguish between them

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4
Q

What are the 3 components that make up the meninges?

A
  • dura mater
  • arachnoid mater
  • pia mater
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5
Q

What is aseptic meningitis?

A

Meningitis where a pyogenic bacterial source is not to blame

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6
Q

What would you find in aseptic meningitis?

A
  • clinical picture of meningitis
  • white cell count > 5x10^6/L (5/mm^3) in CSF
  • negative bacterial culture of the CSF
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7
Q

What are the causes of aseptic meningitis?

A
  • viruses = most common cause
  • partially treated bacterial meningitis
  • listeria
  • TB
  • syphilis
  • malignancy
  • autoimmune conditions
  • drugs
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8
Q

Describe the simple virus structure

A
  • nucleic acid core

- capsid = protein coat, made up of capsomeres (subunits)

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9
Q

As well as the nucleic acid core and the protein coat, some viruses may have what?

A
  • lipid envelope (derived from host cell membrane)

- some contain other proteins/enzymes

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10
Q

What are the variations in the nucleic acid of a virus?

A

DNA or RNA

  • single stranded or double stranded
  • linear or circular (eg. Hep B DNA)
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11
Q

What do the viral proteins do?

A

Form the capsid/membrane projections

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12
Q

What do viral enzymes do?

A
  • replicating genetic material
  • influencing transcription
  • protein modification
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13
Q

How common is viral meningitis?

A

Common, especially in children/neonates

  • incidence = 5-15 cases per 100,000
  • 3400 hospital cases in UK 2009-2010
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14
Q

At what age are the 2 peaks of hospital admission with viral meningitis?

A
  • neonates

- around age 5

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15
Q

What is the leading cause of viral meningitis?

A

Enteroviruses

  • echovirus
  • coxsackie virus
  • parecho virus
  • enteroviruses 70 and 71
  • poliovirus
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16
Q

Which enteroviruses are very rare in the UK?

A
  • enteroviruses 70 and 71

- poliovirus

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17
Q

Herpes viruses can also cause viral meningitis. Which types?

A
  • herpes simplex virus 2
  • varicella zoster virus
  • cytomegalovirus, epstein barr virus
  • HHV6, HHV7
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18
Q

As well as enteroviruses and herpes viruses, what other viruses can cause viral meningitis?

A
  • arboviruses (eg. Japenese encephalitis virus)
  • mumps virus
  • HIV
  • adenovirus
  • measles
  • influenza
  • parainfluenza type 3
  • lymphocytic choriomeningitis virus (LCMV)
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19
Q

What is very important to take into account when diagnosing viral meningitis?

A
  • travel history
  • sexual history
  • if immunocompromised
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20
Q

In what proportion of cases of viral meningitis is the cause unknown?

A

35%

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21
Q

Describe the pathogenesis in viral meningitis?

A
  • colonisation of mucosal surfaces
  • invasion of epithelial surface
  • replication in cells
  • dissemination and CNS invasion
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22
Q

How might viral infection disseminate and cause CNS invasion?

A
  • via cerebral microvascular endothelial cells
  • via choroid plexus epithelium
  • spread along the olfactory nerve
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23
Q

What are the symptoms of viral meningitis mainly due to?

A

The inflammatory response in the CNS

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24
Q

How do viruses enter the CNS?

A

Either via the blood stream (haematogenous spread) eg. enteroviruses,

or by travelling up peripheral nerves (neurotropic) eg. HSV and VZV

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25
Q

What are the general features of a typical presentation of viral meningitis?

A
  • fever
  • ‘meningism’ = headache, neck stiffness, photophobia
  • sometimes ‘viral’ prodrome = lethargy, myalgias, arthralgias, sore throat, D&V, rash)
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26
Q

Is it difficult to distinguish between viral and bacterial meningitis?

A

Usually very difficult to distinguish clinically between viral and bacterial meningitis

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27
Q

How does viral meningitis present in children?

A

Signs may be absent in neonates/infants

Look for nuchal rigidity (neck stiffness) and bulging anterior fontanelle

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28
Q

What are the 3 examination findings in viral meningitis?

A
  1. Kernig’s sign
  2. Brudzinski’s sign
  3. Nuchal rigidity
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29
Q

What is Kernig’s sign?

A

With hip and knee flexed to 90 degrees, the knee cannot be extended due to pain/stiffness in the hamstrings

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30
Q

What is Brudzinski’s sign?

A

Flexing the neck causes the hips and knees to flex

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31
Q

What is nuchal rigidity?

A

Resistance to flexion of the neck

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32
Q

What blood tests would you do as part of viral meningitis investigation?

A
  • FBC, U&E, CRP, clotting

- blood culture

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33
Q

Why would you do a CT head as part of viral meningitis investigations?

A

To look for evidence of raised intra-cranial pressure and alternative diagnosis eg. mass lesion, subarachnoid haemorrhage

Indicated before lumbar puncture in specific circumstances

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34
Q

What would you look for in a lumbar puncture (ASAP) as part of viral meningitis investigations?

A
  • microscopy, culture, sensitivity (MC&S)
  • protein
  • glucose (must check blood culture at same time)
  • viral PCR (enteroviruses, HSV, VZV)
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35
Q

What 2 things in a blood test are often normal in viral meningitis?

A
  • white cell count

- CRP

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36
Q

Why should clotting be checked in viral meningitis investigations?

A

To ensure it is safe to carry out a lumbar puncture

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37
Q

What are the 3 main investigations you should do in viral meningitis?

A
  • blood tests
  • CT head
  • lumbar puncture
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38
Q

Why should a CT head be performed before an LP in certain patients?

A

To rule out signs of intracranial pressure as if present, an LP is contraindicated

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39
Q

Why is an LP contraindicated in patients with raised intracranial pressure?

A

Because removing the CSF can cause the brain to herniate through the foramen magnum (called ‘coning’)

40
Q

Which features in a case of suspected meningitis indicate the need for CT before LP?

A
  • immunocompromised state
  • history of previous CNS disease
  • new onset seizure (within one week of presentation)
  • papilloedema
  • abnormal level of consciousness
  • focal neurological deficit

OR (diff. guidelines)

  • focal neurological signs
  • presence of papilloedema
  • continuous or uncontrolled seizures
  • GCS
41
Q

Unless the patient has signs of shock or severe sepsis, an LP should be performed when?

A

Within an hour or arrival at hospital (preferably before antibiotics are administered)

42
Q

What is the ‘gold standard’ test for viral meningitis?

A

Viral PCR

43
Q

What are the white cell count CSF findings in viral meningitis?

A
  • lymphocytic, usually
44
Q

What is the normal CSF protein level?

A

0.2-0.4g/L

45
Q

What is the CSF protein level in viral meningitis?

A

Normal or mildly elevated (0.5-1.0g/L)

46
Q

What is the normal CSF glucose ratio? (ratio of CSF:plasma)

A

50-66%

47
Q

What is the CSF glucose level in viral meningitis?

A

Normal, or slightly low

48
Q

What is pleocytosis?

A

Increased WBC count in CSF

49
Q

What other microbiological investigations are used in viral meningitis?

A

Throat swab and/or stool sample
- enterovirus PCR

Serology

  • mumps
  • EBV/CMV
  • HIV
  • other viruses are indicated eg. travel-related
50
Q

What treatment should you use if any risk of bacterial meningitis?

A

Start appropriate IV antibiotics eg. cefotaxime

51
Q

What is the treatment for viral meningitis?

A

No evidence to support use of any specific treatment (though some to treat HSV and VZV with aciclovir)

Mainly supportive therapy (e.g. analgesia and antipyretics)

52
Q

What is the prognosis for viral meningitis?

A

Generally good prognosis

but growing evidence of long term symptoms in some people eg. headaches, cognitive dysfunction

53
Q

Is viral meningitis a notifiable disease?

A

Yes!

Inform local public health department

54
Q

Enteroviral meningitis is the commonest viral meningitis in the UK. When are the classical epidemics?

A

Late summer/autumn

55
Q

What are the common symptoms of enteroviral meningitis?

A
  • fever
  • vomiting
  • anorexia
  • rash
  • upper respiratory tract symptoms
56
Q

What is the treatment and recovery for enteroviral meningitis?

A
  • no specific treatment

- full recovery normal

57
Q

What are the 2 forms of HSV (herpes simplex virus) and what do they cause?

A

HSV1 = cold sores and viral encephalitis

HSV 2 = genital herpes and meningitis

58
Q

What is the 2nd commonest cause of viral meningitis?

A

HSV2

Can follow primary infection (after genital lesions) or occur during/between relapses

59
Q

What is the treatment for HSV meningitis?

A

No evidence that aciclovir is effective

60
Q

What is Mollaret’s meningitis?

A
  • recurrent aseptic meningitis

- wide differential but major cause = HSV2

61
Q

What diseases does VZV cause?

A

primary = chickenpox (varicella)

secondary = shingles (zoster)

Meningitis unusual but can occur during chickenpox, shingles (so look for rash), on its own or after vaccination

62
Q

Should aciclovir be used in VZV meningitis?

A

No evidence that it is beneficial but may be indicated for the rash

Complete recovery normal

63
Q

Mumps meningitis occurs in how many mumps cases?

A

10-30%

64
Q

When do CNS symptoms occur in mumps?

A

5 days after onset of parotitis

65
Q

What are the other features of mumps meningitis?

A
  • abdominal pain

- orchitis

66
Q

What is the treatment and recovery for mumps meningitis?

A
  • no specific treatment
  • full recovery normal
  • preventable with vaccination
67
Q

What is orchitis? (a symptoms of mumps meningitis)

A

Inflammation of one or both of the testicles

68
Q

Can meningitis occur in HIV?

A

Yes, can occur as part of primary infection

69
Q

What are the associated features of meningitis in HIV?

A

= like glandular fever

  • fever
  • lymphadenopathy
  • pharyngitis
  • rash

Self-limiting symptoms

70
Q

What is the main cause of viral encephalitis?

A

Herpes simplex virus 1 & 2

90% are HSV1

71
Q

Other than HSV1, what are the other viral causes of viral encephalitis?

A
  • VZV, EBV, CMV
  • adenovirus
  • measles
  • mumps
  • enteroviruses (including polio)
  • arboviruses
  • influenza
  • rubella
  • HIV
  • rabies
72
Q

Other than viral causes, what are the other causes of encephalitis?

A
  • bacteria eg. strep pneumoniae, neisseria meningitidis, TB
  • malignancy (paraneoplastic)
  • autoimmune
  • acute disseminated encephalomyopathy (ADEM)
  • other immune-mediated
73
Q

In what proportion of encephalitis cases is the cause unknown?

A

37%

74
Q

Viral encephalitis has a different clinical presentation from meningitis. What are the major features?

A
  • altered mental state (confusion/bizarre behaviour/coma)
  • fever
  • headache
  • meningism (may be absent)
75
Q

Focal neurology may or may not be present in viral encephalitis. What does it include?

A
  • seizures
  • weakness
  • dysphasia/aphasia
  • cranial nerve palsy
  • ataxia
76
Q

Viral encephalitis is a serious illness and if there is any doubt eg. any change in conscious level then what should happen?

A

The patient should be started on IV aciclovir

77
Q

What are the main investigations used in suspicion of viral encephalitis?

A
  • blood tests
  • CT
  • MRI
  • lumbar puncture
  • EEG
78
Q

What blood tests should be done in viral encephalitis?

A
  • FBC, U&ES, CRP, clotting-
  • (blood cultures)
  • serology
79
Q

What is seen on an MRI in viral encephalitis?

A

May see changes typical of HSV encephalitis

80
Q

Why is CT used in viral encephalitis investigations?

A

Likely to be necessary before LP

81
Q

Why is a lumbar puncture useful in viral encephalitis investigations?

A
  • microscopy
  • culture and sensitivity
  • protein/glucose
  • viral PCR
82
Q

What is seen on an EEG in viral encephalitis?

A

In HSV encephalitis, 75% will show abnormal temporal lobe activity

83
Q

What are the CSF findings in viral encephalitis?

A

Same as in viral meningitis

84
Q

What does HSE stand for?

A

Herpes simplex encephalitis

85
Q

How is viral encephalitis treated?

A

High does IV aciclovir

  • 10mg/kg tds
  • 14-21 days
  • start on clinical suspicion, do not wait for CSF results as it is a medical emergency
  • oral switch not recommended
  • insufficient evidence to recommend steroids
86
Q

Describe the epidemiology of HSE

A
  • rare
  • high mortality if untreated
  • bimodal distribution (increased incidence 50 years)
  • equally spread between sexes
87
Q

Describe the pathogenesis of HSE

A
  • primary infection = direct transmission of the virus along neural/olfactory pathways
    OR
  • reactivation in the trigeminal ganglia
  • acute focal necrotising encephalitis
  • inflammation/swelling of brain tissue
88
Q

What is the mortality rate of HSE if untreated?

A

70%

89
Q

What is the mortality rate of HSE if treated?

A

Remains high

  • 28% at 18 months
  • if GCS
90
Q

Survivors of HSE frequently have neurological sequelae such as…

A
  • paralysis
  • speech loss
  • personality change
91
Q

What is acute disseminated encephalomyelopathy (ADEM)?

A
  • immune-mediated CNS demyelination
  • clinical features same as encephalitis
  • CSF findings = viral meningitis
92
Q

ADEM can follow what?

A

Viral illness or vaccination eg. influenza

93
Q

Which investigation is useful in ADEM?

A

MRI

94
Q

What is the treatment for ADEM?

A

Steroids/other immunosuppressants

95
Q

What is the recovery like for ADEM?

A

Variable

96
Q

Viral meningitis is often clinically indistinguishable from bacterial meningitis. What should you do if there is any doubt?

A

Treat as bacterial and then review antibiotics with LP result

97
Q

What should you always remember to do when you take an LP?

A

Take a concurrent serum glucose sample and work out ratio

5. CP - Central Nervous System Infections (3 decks)

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