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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
What are the general features of a typical presentation of viral meningitis?
- fever - 'meningism' = headache, neck stiffness, photophobia - sometimes 'viral' prodrome = lethargy, myalgias, arthralgias, sore throat, D&V, rash)
26
Is it difficult to distinguish between viral and bacterial meningitis?
Usually very difficult to distinguish clinically between viral and bacterial meningitis
27
How does viral meningitis present in children?
Signs may be absent in neonates/infants Look for nuchal rigidity (neck stiffness) and bulging anterior fontanelle
28
What are the 3 examination findings in viral meningitis?
1. Kernig's sign 2. Brudzinski's sign 3. Nuchal rigidity
29
What is Kernig's sign?
With hip and knee flexed to 90 degrees, the knee cannot be extended due to pain/stiffness in the hamstrings
30
What is Brudzinski's sign?
Flexing the neck causes the hips and knees to flex
31
What is nuchal rigidity?
Resistance to flexion of the neck
32
What blood tests would you do as part of viral meningitis investigation?
- FBC, U&E, CRP, clotting | - blood culture
33
Why would you do a CT head as part of viral meningitis investigations?
To look for evidence of raised intra-cranial pressure and alternative diagnosis eg. mass lesion, subarachnoid haemorrhage Indicated before lumbar puncture in specific circumstances
34
What would you look for in a lumbar puncture (ASAP) as part of viral meningitis investigations?
- microscopy, culture, sensitivity (MC&S) - protein - glucose (must check blood culture at same time) - viral PCR (enteroviruses, HSV, VZV)
35
What 2 things in a blood test are often normal in viral meningitis?
- white cell count | - CRP
36
Why should clotting be checked in viral meningitis investigations?
To ensure it is safe to carry out a lumbar puncture
37
What are the 3 main investigations you should do in viral meningitis?
- blood tests - CT head - lumbar puncture
38
Why should a CT head be performed before an LP in certain patients?
To rule out signs of intracranial pressure as if present, an LP is contraindicated
39
Why is an LP contraindicated in patients with raised intracranial pressure?
Because removing the CSF can cause the brain to herniate through the foramen magnum (called 'coning')
40
Which features in a case of suspected meningitis indicate the need for CT before LP?
- 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
Unless the patient has signs of shock or severe sepsis, an LP should be performed when?
Within an hour or arrival at hospital (preferably before antibiotics are administered)
42
What is the 'gold standard' test for viral meningitis?
Viral PCR
43
What are the white cell count CSF findings in viral meningitis?
- lymphocytic, usually
44
What is the normal CSF protein level?
0.2-0.4g/L
45
What is the CSF protein level in viral meningitis?
Normal or mildly elevated (0.5-1.0g/L)
46
What is the normal CSF glucose ratio? (ratio of CSF:plasma)
50-66%
47
What is the CSF glucose level in viral meningitis?
Normal, or slightly low
48
What is pleocytosis?
Increased WBC count in CSF
49
What other microbiological investigations are used in viral meningitis?
Throat swab and/or stool sample - enterovirus PCR Serology - mumps - EBV/CMV - HIV - other viruses are indicated eg. travel-related
50
What treatment should you use if any risk of bacterial meningitis?
Start appropriate IV antibiotics eg. cefotaxime
51
What is the treatment for viral meningitis?
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
What is the prognosis for viral meningitis?
Generally good prognosis | but growing evidence of long term symptoms in some people eg. headaches, cognitive dysfunction
53
Is viral meningitis a notifiable disease?
Yes! Inform local public health department
54
Enteroviral meningitis is the commonest viral meningitis in the UK. When are the classical epidemics?
Late summer/autumn
55
What are the common symptoms of enteroviral meningitis?
- fever - vomiting - anorexia - rash - upper respiratory tract symptoms
56
What is the treatment and recovery for enteroviral meningitis?
- no specific treatment | - full recovery normal
57
What are the 2 forms of HSV (herpes simplex virus) and what do they cause?
HSV1 = cold sores and viral encephalitis HSV 2 = genital herpes and meningitis
58
What is the 2nd commonest cause of viral meningitis?
HSV2 Can follow primary infection (after genital lesions) or occur during/between relapses
59
What is the treatment for HSV meningitis?
No evidence that aciclovir is effective
60
What is Mollaret's meningitis?
- recurrent aseptic meningitis | - wide differential but major cause = HSV2
61
What diseases does VZV cause?
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
Should aciclovir be used in VZV meningitis?
No evidence that it is beneficial but may be indicated for the rash Complete recovery normal
63
Mumps meningitis occurs in how many mumps cases?
10-30%
64
When do CNS symptoms occur in mumps?
5 days after onset of parotitis
65
What are the other features of mumps meningitis?
- abdominal pain | - orchitis
66
What is the treatment and recovery for mumps meningitis?
- no specific treatment - full recovery normal - preventable with vaccination
67
What is orchitis? (a symptoms of mumps meningitis)
Inflammation of one or both of the testicles
68
Can meningitis occur in HIV?
Yes, can occur as part of primary infection
69
What are the associated features of meningitis in HIV?
= like glandular fever - fever - lymphadenopathy - pharyngitis - rash Self-limiting symptoms
70
What is the main cause of viral encephalitis?
Herpes simplex virus 1 & 2 90% are HSV1
71
Other than HSV1, what are the other viral causes of viral encephalitis?
- VZV, EBV, CMV - adenovirus - measles - mumps - enteroviruses (including polio) - arboviruses - influenza - rubella - HIV - rabies
72
Other than viral causes, what are the other causes of encephalitis?
- bacteria eg. strep pneumoniae, neisseria meningitidis, TB - malignancy (paraneoplastic) - autoimmune - acute disseminated encephalomyopathy (ADEM) - other immune-mediated
73
In what proportion of encephalitis cases is the cause unknown?
37%
74
Viral encephalitis has a different clinical presentation from meningitis. What are the major features?
- altered mental state (confusion/bizarre behaviour/coma) - fever - headache - meningism (may be absent)
75
Focal neurology may or may not be present in viral encephalitis. What does it include?
- seizures - weakness - dysphasia/aphasia - cranial nerve palsy - ataxia
76
Viral encephalitis is a serious illness and if there is any doubt eg. any change in conscious level then what should happen?
The patient should be started on IV aciclovir
77
What are the main investigations used in suspicion of viral encephalitis?
- blood tests - CT - MRI - lumbar puncture - EEG
78
What blood tests should be done in viral encephalitis?
- FBC, U&ES, CRP, clotting- - (blood cultures) - serology
79
What is seen on an MRI in viral encephalitis?
May see changes typical of HSV encephalitis
80
Why is CT used in viral encephalitis investigations?
Likely to be necessary before LP
81
Why is a lumbar puncture useful in viral encephalitis investigations?
- microscopy - culture and sensitivity - protein/glucose - viral PCR
82
What is seen on an EEG in viral encephalitis?
In HSV encephalitis, 75% will show abnormal temporal lobe activity
83
What are the CSF findings in viral encephalitis?
Same as in viral meningitis
84
What does HSE stand for?
Herpes simplex encephalitis
85
How is viral encephalitis treated?
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
Describe the epidemiology of HSE
- rare - high mortality if untreated - bimodal distribution (increased incidence 50 years) - equally spread between sexes
87
Describe the pathogenesis of HSE
- 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
What is the mortality rate of HSE if untreated?
70%
89
What is the mortality rate of HSE if treated?
Remains high - 28% at 18 months - if GCS
90
Survivors of HSE frequently have neurological sequelae such as...
- paralysis - speech loss - personality change
91
What is acute disseminated encephalomyelopathy (ADEM)?
- immune-mediated CNS demyelination - clinical features same as encephalitis - CSF findings = viral meningitis
92
ADEM can follow what?
Viral illness or vaccination eg. influenza
93
Which investigation is useful in ADEM?
MRI
94
What is the treatment for ADEM?
Steroids/other immunosuppressants
95
What is the recovery like for ADEM?
Variable
96
Viral meningitis is often clinically indistinguishable from bacterial meningitis. What should you do if there is any doubt?
Treat as bacterial and then review antibiotics with LP result
97
What should you always remember to do when you take an LP?
Take a concurrent serum glucose sample and work out ratio

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

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