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Clinical Pathology > 25 - Viral Meningitis/Encephalitis > Flashcards

25 - Viral Meningitis/Encephalitis Flashcards

1
Q

Aseptic meningitis - clinical picture

A

White cell count >5x10^6 per litre in CSF
Negative bacterial culture of CSF
Viruses most common cause

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2
Q

Virus info

A

Basic infectious particle = virion
Simple virus structure
Nucleic acid with capsid maybe w/ lipid envelope/ other proteins or enzymes

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3
Q

Aetiology of meningitis

A 
Enteroviruses (leading cause)
Herpes viruses
Arboviruses
Mumps Virus
HIV
Adenovirus
Measles
Influenza
Parainfluenza type 3
Lymphocytic choriomeningitis virus (LCMV)
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4
Q

Types of enteroviruses

A 
Echoviruses
Coxsackie virus
Parecho virus
Enterovirus (70&71)
Polio virus
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5
Q

Types of herpes viruses

A 
HSV
VZV (varicella zoster)
CMV
Epstein Barr Virus (EBV)
HHV6, HHV7
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6
Q

Pathogenesis of meningitis

A 
Colonisation of mucosal surfaces
Invasion of epithelial surface
Replication in cells
Dissemination and CNS invasion
Symptoms mainly due to inflammatory response in the CNS
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7
Q

How does it invade the CNS

A

Via cerebral microvascular endothelial cells
Via choroid plexus epithelium
Spread along the olfactory nerve

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8
Q

Meningitis - clinical presentation

A

Fever
Meningism - headache, neck stiffness, photophobia
Sometimes viral prodome (lethargy, myalgias, arthralgias, sore throat, D&V, rash)

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9
Q

Meningitis - clinical presentation in children

A

Neonates - signs might be absent
Look for nuchal rigidity (neck stiffness)
Bulging anterior fontanelle

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10
Q

Meningitis - examinations

A

Kernig’s sign
Brudzinski’s sign
Nuchal rigidity

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11
Q

Kernig’s sign

A

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

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12
Q

Brudzinski’s sign

A

Flexing the neck causes the hips and knees to flex

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13
Q

Nuchal rigidity

A

Resistance to flexion of the neck

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14
Q

Meningitis - investigations

A

Blood tests - FBC, U&E, CRP, clotting + blood culture
CT head
Lumbar puncture - should be within an hour

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15
Q

Meningitis - what would CTing head see?

A

Raised intra-cranial pressure

e.g. mass lesion, subarachnoid haemorrhage

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16
Q

Meningitis - lumbar puncture (LP) - why?

A

Microscopy, culture, sensitivity (MC&S)
Protein
Glucose (MUST CHECK GLUCOSE AT SAME TIME)
Viral PCR: enteroviruses, HSV, VZV

17
Q

CSF findings in viral meningitis

A

White cell count: lymphocytic mildly elevated

Glucose (ratio CSF:plasma) normal is around 50% - viral it ranges from normal to slightly low

18
Q

Bacterial vs viral meningitis

A 
Higher opening pressure in bac
Higher WBC count
WBC differential = >80% PMN
More protein
Both around 40% glucose of serum
19
Q

What other microbiology investigations could you get?

A

Throat swab/stool sample for entervirus PCR

Serology - mumps, EBV,CMV,HIV, other travel-related

20
Q

Treatments and outcome

A

Start approprite IV antibiotics if risk of bacterial meningitis
No specific treatment for viral (could use aciclovir)
Mainly supportive therapy (analgesia and antipyretics)
Good prognosis
NOTIFIABLE DISEASE FOR PHE

21
Q

Enteroviral meningitis - symptoms, treatments, prognosis

A 
Commonest cause
Late summer/autumn epidemics
Fever, vomiting, anorexia, rash, URT
No specific treatment 
Full recovery normal
22
Q

HSV

A

2 forms - 1&2
HSV 2 is 2nd commonest cause of viral meningitis
Mollaret’s meningitis - recurrent aseptic meningitis but major cause = HSV2

23
Q

HSV1

A

Causes cold sores and viral encephalitis

24
Q

HSV2

A

Causes genital herpes and meningitis

25
Q

VZV

A

Primary = chickenpox (varicella)
Secondary = shingles (zoster)
No evidence aciclovir is beneficial
Complete normal recovery

26
Q

Mumps

A 
10-30% are mumps cases
CNS symptoms 5 days after onset of parotitis
Features: ab pain, orchitis
No specific treatment
Full recovery normal
Preventable w/ vaccination
27
Q

Viral encephalitis - aetiology

A 
HSV - 90% are HSV1
EBV
Measles
Mumps
Enteroviruses inc. polio
Bacteria - strep pneumoniae, neisseria meningitidis, TB
Acute disseminated encephalomyopathy (ADEM)
Unknown = 37%
28
Q

Viral encephalitis - clinical presentation

A

Altered mental state is key - low GCS
Fever
Headache
Meningism

Focal neurology: seizures, weakness, dysphasia, cranial nerve palsy, ataxia

29
Q

Viral encephalitis - investigations

A

Bloods tests- FBC, U&E, CRP, clotting & blood cultures
Serology
CT - necessary before LP
MRI - may see changes typical of HSV encephalitis
LP - microscopy, culture and sensitivity, protein/glucose, viral PCR
EEG - 75% will show abnormal temporal lobe activity

30
Q

CSF findings are different or same comparing viral encephalitis with meningitis?

A

Same

31
Q

Viral encephalitis - treatment

A

High dose IV aciclovir for 14-21 days
Start on clinical suspicion do not wait for CSF results
Oral switch not recommended

32
Q

Herpes simplex encephalitis

A

Rare, but mortality high in untreated
MRI shows clearer signs
Bimodal distribution, 50 yo
Equally spread in gender

33
Q

HSE pathogenesis

A

Primary infection vs reactivation - direct transmission of the virus along neural/olfactory pathways vs reactivation in the trigeminal ganglia
Acute focal necrotising encephalitis
Inflammation / swelling of brain tissue

34
Q

Viral encephalitis - outcome

A

Mortality untreated - 70%
Mortality is treated is high - 28% at 18months
If GCS

35
Q

Acute disseminated encephalomyelopathy (ADEM)

A 
immune-mediated CNS demyelination
Can follow viral illness or vaccination
Clinical features same as encephalitis
CSF findings = viral meningitis 
MRI helpful
Treatment is steroids/other immunosuppressants
Recovery variable
36
Q

Take home messages

A

Viral meningitis often indistinguishable from bacterial - need LP
LP essential for diagnosis of both meningitis & encephalitis
Always take concurrent serum glucose sample when do LP
HSE is medical emergency needs IV aciclovir

Clinical Pathology (65 decks)

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