Viral meningitis/encephalitis Flashcards

1
Q

What is encephalitis?

A

Inflammation of the brain parenchyma - grey and white matter

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2
Q

What is meningo-encephalitis?

A

Inflammation of the brain and meninges

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3
Q

Are encephalitis and meningitis easily distinguishable clinically?

A

No

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4
Q

What is meant by aseptic meningitis?

A

1) Clinical picture of meningitis
2) White cell count above normal in CSF (>5x10^6/L)
3) Negative bacterial culture of the CSF

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5
Q

What are the most common cause of aseptic meningitis?

A

Viruses

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6
Q

Other than viruses name 7 other causes of aseptic meningitis?

A

1) Partially treated bacterial meningitis
2) Listeria
3) TB
4) Syphilis
5) Malignancy
6) Autoimmune conditions
7) Drugs

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7
Q

What is a virion

A

basic infectious particle

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8
Q

What is the simple structure of a virus?

A

1) Nucleic acid - may be DNA or RNA and single or double stranded with multiple or just one strand - linear or circular
2) Capsid - protein coat made up of capsomeres (subunits)

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9
Q

Other than the simple virus structure what other 2 things can some viruses contain?

A

1) Some have a lipid envelope (derived from host cell membrane as they bud off)
2) Some contain other proteins / enzymes

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10
Q

Give 3 possible functions of the enzymes found in some viruses?

A

1) Replicating genetic material
2) Influencing transcription (by host material)
3) Protein modification

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11
Q

In which group is viral meningitis most common, what are the 2 peaks of hospital admission?

A

Neonates and children
Peaks in:
1) Neonates
2) Aged ~5years

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12
Q

What is the incidence of viral meningitis per 100,000?

A

5-15 cases per 100,000

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13
Q

What kind of viruses are the leading cause of viral meningitis, give 5 examples of that kind?

A

Enteroviruses

1) Echoviruses
2) Coxsackie virus
3) Parecho viruses
4) Enteroviruses 70 and 71
5) Poliovirus

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14
Q

Other than enteroviruses what other group of viruses commonly cause viral meningitis?

A

Herpes viruses

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15
Q

Give 5 examples of herpes viruses which commonly cause viral meningitis?

A

1) Herpes simplex virus 2
2) Varicella zoster virus
3) Cytomegalovirus
4) HHV6, HHV7
5) Epstein barr virus

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16
Q

Does HSV1 or 2 more commonly cause viral meningitis?

A

HSV2

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17
Q

What is the name of the Japanese encephalitis virus?

A

Arboviruses

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18
Q

Other than enteroviruses and herpes viruses which 7 other viruses cause viral meningitis?

A

1) Mumps Virus
2) HIV
3) Adenovirus
4) Measles
5) Influenza
6) Parainfluenza type 3
7) Lymphocytic choriomeningitis virus (LCMV)

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19
Q

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

A

35%

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20
Q

What are the symptoms mainly attributable to in viral meningitis?

A

Bodies reaction to the virus - the inflammatory response in the CNS

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21
Q

What are the 4 steps in the pathogenesis of viral meningitis?

A

1) Colonisation of mucosal surfaces
2) Invasion of epithelial surface
3) Replication in cells
4) Dissemination and CNS invasion

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22
Q

What are the 3 modes of CNS invasion for viral causes of meningitis?

A

1) Via cerebral microvascular endothelial cells
2) Via choroid plexus epithelium
3) Spread along the olfactory nerve

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23
Q

What 3 symptoms make up meningism?

A

1) Headache
2) Neck stiffness
3) Photophobia

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24
Q

What are the 3 main features of a clinical presentation of viral meningitis?

A

1) Fever
2) Meningism (headache, neck stiffness, photophobia)
3) Sometimes viral prodrome (lethargy, myalgia, arthralgias, sore throat, D&V, rash)

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25
Q

What 6 features can be seen in a viral prodrome?

A

1) Lethargy
2) Myalgia
3) Arthralgia
4) Sore throat
5) D&V
6) Rash

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26
Q

How may the clinical presentation of viral meningitis differ in neonates/infants?

A

1) Meningeal signs may be absent
2) Look for nuchal rigidity (neck stiffness)
3) May see a bulging anterior fontanelle (from raised ICP)

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27
Q

What is Kernig’s sign (found on examination for meningitis)?

A

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

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28
Q

What is Brudzinski’s sign (found on examination for meningitis)?

A

Flexing the neck causes the hips and knees to flex

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29
Q

What is nuchal rigidity?

A

Resistance to flexion of the neck

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30
Q

What blood tests would be carried out when investigating meningitis? 6

A

1) FBC
2) U&E
3) CRP
4) Clotting (need to know OK if going to do a LP)
5) Blood culture
6) Blood glucose (to compare to CSF glucose)

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31
Q

Why would a CT head be carried out in investigating viral meningitis?

A

To look for evidence of raised ICP (important to know if going to do a LP - and is therefore indicated before an LP in certain circumstances) and alternative diagnosis

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32
Q

What is the first investigation which should be carried out ideally?

A

Lumbar puncture

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33
Q

For what 4 reasons would a lumbar puncture be carried out in suspected viral meningitis?

A

1) Microscopy, culture and sensitivity (MC&S)
2) Protein
3) Glucose (must check blood glucose at the same time)
4) Viral PCR: enteroviruses, HSV, VZV

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34
Q

Why must a blood glucose be done when analysing the CSF glucose?

A

CSF glucose alone is irrelevant - needs to be compared to plasma glucose, without knowing the plasma glucose the CSF glucose can therefore not be interpreted

35
Q

What is pleocytosis?

A

White cells in a fluid (here refers to white cells in CSF)

36
Q

What are the CSF findings in viral meningitis in terms of white cells, protein and glucose?

A

White cell count - pleocytosis
Lymphocytic, usually less than 500 (as opposed to neutrophilic which would be more predominant in bacterial meningitis)
May initially be a predominance of neutrophils (first 24 hours)
Protein (0.2-0.4 g/L) - normal or mildly elevated (0.5-1.0)
Glucose (ratio of CSF: plasma - normal is 50-66%) - in viral meningitis is normal or slightly low

37
Q

What are the CSF findings in bacterial meningitis in terms of white cells, protein and glucose?

A

White cells - higher in bacterial (100-20,000)
>80% PMC (pleomorphic cells - neutrophils)
Protein raised
Glucose reduced

38
Q

Other than CSF and blood cultures what 2 other microbiological investigations could be carried out in suspected viral meningitis, what viruses would they be looking for?

A

1) Throat swan and/or stool sample
- Enterovirus PCR
2) Serology
- Mumps, EBV/CMV, HIV, Other viruses as indicated eg. travel related

39
Q

What is the treatment for viral meningitis - what treatment should be started straight away?

A

Start appropriate IV Abx (eg. cefotaxime) if any risk of bacterial meningitis
Mainly supportive therapy (eg. analgesia and anti-pyretics)
(Also a notifiable disease)

40
Q

What anti-viral is sometimes used to treat viral meningitis, is there any research to support its use?

A

Aciclovir (in HSV and VZV) - but no evidence to support use of any specific treatment

41
Q

What is the prognosis of viral meningitis?

A

Generally good - although growing evidence of long term symptoms in some people eg. headaches and cognitive dysfunction

42
Q

What is the commonest cause of viral meningitis in the UK, what seasonal epidemics are seen?

A

Enteroviral meningitis

Classically late summer/autumn epidemics

43
Q

In addition to the general presenting symptoms in meningitis what 5 other symptoms are common in enteroviral meningitis?

A

1) Fever
2) Vomiting
3) Anorexia
4) Rash
5) Upper respiratory tract infections

44
Q

What is the treatment and prognosis for enteroviral meningitis?

A

No specific treatment

Full recovery is normal

45
Q

What are the 2 forms of herpes simplex virus and what does each commonly cause?

A

1) HSV1 - causes cold sores and viral encephalitis

2) HSV2 - causes genital herpes and meningitis

46
Q

What is the 2nd most common cause of viral meningitis?

A

HSV2

47
Q

When does HSV2 viral meningitis commonly occur in relation to the primary infection with HSV2?

A

Can follow the primary infection (3-12/7 after genital lesions)
Or can occur during/between relapses

48
Q

Is there any specific treatment for HSV2 viral meningitis?

A

Aciclovir is sometimes used but there is not evidence to suggest that its effective

49
Q

What is Mollaret’s meningitis?

A

Recurrent aseptic meningitis

50
Q

What is the cause of Mollaret’s meningitis?

A

Major causes is HSV2

51
Q

What primary and secondary diseases does the varicella zoster virus cause?

A

Primary - chicken pox

Secondary - shingles

52
Q

Is meningitis caused by VZV common?

A

Unusual but can occur during chicken pox, shingles or on its own or after vaccination

53
Q

Is there any specific treatment for VZV meningitis?

A

Aciclovir sometimes used but no evidence that it is effective

54
Q

What is the prognosis of VZV meningitis?

A

Complete recovery is normal

55
Q

What percentage of cases of mumps lead to mumps meningitis?

A

10-30%

56
Q

How long after parotitis do the CNS symptoms of mumps meningitis present?

A

5 days

57
Q

In addition to the general symptoms of meningitis what 2 other symptoms are common in mumps meningitis?

A

1) Abdominal pain

2) Orchitis (inflammation of testicles)

58
Q

Is there any treatment for mumps meningitis?

A

No specific treatment but an available vaccine

59
Q

What is the prognosis of mumps meningitis?

A

Full recovery is normal

60
Q

HIV is another cause of viral meningitis when in the course of infection does this tend to occur?

A

As part of the primary infection

61
Q

What are the 4 associated features of HIV meningitis?

A

1) Fever
2) Lymphadenopathy
3) Pharyngitis
4) Rash

62
Q

Is there any treatment for HIV meningitis?

A

No - the symptoms are self-limiting

63
Q

What is the most common cause of viral encephalitis?

A

Herpes simplex virus 1 and 2

90% of cases are HSV1

64
Q

Other than HSV what are the 11 other viral causes of viral encephalitis?

A

1) VZV
2) EBV
3) CMV
4) Measles
5) Mumps
6) Enteroviruses (including polio)
7) Arboviruses
8) Influenza
9) Rubella
10) HIV
11) Rabies

65
Q

Other than viral causes what are the 5 other causes of encephalitis?

A

1) Bacteria (strep pneumonia, Neisseria meningitidis, TB)
2) Malignancy (paraneoplastic)
3) Autoimmune
4) Acute disseminated encephalomyopathy (ADEM)
5) Other immune-mediated

66
Q

In what percentage of cases of encephalitis is the cause unknown?

A

37%

67
Q

What are the 4 major features of the clinical presentation of encephalitis?

A

1) Altered mental state (confusion/bizarre behaviour - coma)
2) Fever
3) Headache
4) Meningism (may be absent)

68
Q

Focal neurology may also be present in encephalitis, give 5 examples?

A

1) Seizures
2) Weakness
3) Dysphasia/aphasia
4) Cranial nerve palsy
5) Ataxia

69
Q

What 5 investigations would be carried out in encephalitis?

A

1) Blood tests
2) CT - likely to be necessary before LP
3) MRI - may see changes typical of HSV encephalitis (temporal lobe affected)
4) Lumbar puncture
5) EEG

70
Q

What blood tests would be important in investigating encephalitis? 6

A

1) FBC
2) U&E
3) CRP
4) Clotting
5) Blood cultures
6) Serology

71
Q

What 4 investigations would be carried out on the CSF in encephalitis?

A

1) Microscopy
2) Culture and sensitivity
3) Protein/glucose
4) Viral PCR

72
Q

What would an EEG show in 75% of cases of HSV encephalitis?

A

Abnormal temporal lobe activity

73
Q

Do the CSF findings in viral encephalitis and viral meningitis differ?

A

No, they are the same

74
Q

What is the treatment for viral encephalitis?

A

High dose IV acyclovir (10mg/kg tds) for 14-21 days
Start the treatment on clinical suspicion, don’t wait for test results
Oral switch should be avoided

75
Q

Should steroid be used in viral encephalitis?

A

No, there is insufficient evidence to recommend them

76
Q

How common is herpes simplex encephalitis, who is it most common in?

A

Rare

Bimodal distribution - increased incidence 50 years and equally spread through the sexes

77
Q

What is the prognosis for HSE?

A

High mortality if left untreated - 70%

Mortality if treated still remains high - 28% at 18 months

78
Q

How does HSE infect the brain tissue and cause encephalitis?

A

There is direct transmission of the virus along the neural/olfactory pathways
Virus then gets reactivated in the trigeminal ganglia
Get acute focal necrotising encephalitis
Leads to inflammation of brain tissue

79
Q

What finding in HSE is an indicator of poor prognosis and what improves the outcome?

A

If GCS

80
Q

Survivors of HSE can suffer what 3 common long lasting effects?

A

1) Paralysis
2) Speech loss
3) Personality change

81
Q

What is acute disseminated encephalomyelopathy? (ADEM)

A

Immune mediated CNS demyelination

82
Q

What is the link between ADEM and viral infection?

A

The condition although immune mediated can follow a viral infection or vaccination

83
Q

Why is ADEM difficult to distinguish from viral encephalitis, what investigation can be helpful in doing so?

A

CSF findings and clinical presentation are the same as viral encephalitis
MRI can be useful

84
Q

What is the treatment for ADEM, is recovery common?

A

Steroids or other immunosuppressants

Recovery is variable