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Clinical Pathology > Viral menigitis and encephalitis > Flashcards

Viral menigitis and encephalitis 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.

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4
Q

What is ‘aseptic’ meningitis?

A

Clinical picture of meningitis

White cell count >5x10^6/L (5/mm3) in cerebrospinal fluid (CSF)

Negative bacterial culture of the CSF

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5
Q

What are the possible causes of ‘aseptic’ meningitis?

A
  • Partially treated bacterial meningitis
  • Listeria
  • TB
  • Syphilis
  • Malignancy
  • Autoimmune conditions
  • Drugs
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6
Q

What is the epidemiology of viral meningitis?

A

Common, especially in children/neonates

  • Incidence 5-15 cases per 100,000
  • around 3400 hospital cases in UK 2009-10

2 peaks of hospital admission:

  • Neonates
  • around age 5
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7
Q

What is the most common genera of viruses to cause viral meningitis?

A

Enteroviruses

  • Echoviruses
  • Coxsackie viruses
  • Parecho viruses
  • Enteroviruses 70 and 71
  • Poliovirus
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8
Q

Which herpes viruses can cause meningitis?

A

Herpes Simplex Virus 2
- HSV 2&raquo_space; HSV 1

Varicella Zoster Virus (VZV)

Cytomegalovirus (CMV)

Epstein Barr Virus (EBV)

HHV6, HHV7

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9
Q

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

A

35%

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10
Q

What is the pathogenesis of infective meningitis?

A

Colonisation of mucosal surfaces

Invasion of epithelial surface

Replication in cells

Dissemination and CNS invasion

  • Via cerebral microvascular endothelial cells
  • Via choroid plexus epithelium
  • Spread along the olfactory nerve
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11
Q

What causes the symptoms of meningitis?

A

Symptoms mainly due to inflammatory response in the CNS.

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12
Q

What is the clinical presentation of meningitis?

A

Fever

‘Meningism’

  • Headache
  • Neck stiffness
  • Photophobia

Sometimes ‘viral’ prodrome (e.g. lethargy, myalgias, arthralgias, sore throat, D&V, rash)

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13
Q

What is the clinical presentation in neonates?

A

In neonates/infants meningeal signs may be absent

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

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14
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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15
Q

What is Brudzinski’s sign?

A

Flexing the neck causes the hips and knees to flex

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16
Q

What is nuchal rigidity?

A

Resistance to flexion of the neck

17
Q

Under what circumstances should a CT be performed before an LP?

A

If raised intracranial pressure is suspected.

18
Q

What are you looking for in the CSF?

A

Microscopy, Culture, Sensitivity (MC&S)

Protein

Glucose (must check blood glucose at same time)

Viral PCR: enteroviruses, HSV, VZV

19
Q

What are the differences in CSF findings between viral and bacterial meningitis?

A

Opening pressure much higher in bacterial meningitis

WBC count

  • high in bacterial
  • viral = normal
  • 80%PMN in bacterial
  • 50%L & 20%PMN in viral

Protein

  • much higher in bacterial
  • viral = normal

Glucose

  • lower in bacterial
  • viral = normal - low
20
Q

What treatment is given for meningitis?

A

Start appropriate IV antibiotics (e.g. cefotaxime) if any risk of bacterial meningitis

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

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

Generally good prognosis (but growing evidence of long term symptoms in some people, e.g. headaches, cognitive dysfunction)

NOTIFIABLE - inform local public health dept

21
Q

What percentage of mumps cases develop meningitis?

A

10-30%

22
Q

What is the relevance of HIV to meningitis diagnosis?

A

Meningitis can occur as part of primary infection

Associated features (= like glandular fever)

  • Fever
  • Lymphadenopathy
  • Pharyngitis
  • Rash
  • Self-limiting symptoms

Important diagnosis not to miss

23
Q

What is the most common cause of viral encephalitis?

A

HSV 1 in 90% of cases

24
Q

What is the clinical presentation of viral encephalitis?

A

Major features:

  • Altered mental state (confusion/bizarre behaviour -> coma)
  • Fever
  • Headache
  • Meningism (may be absent)

+/- Focal neurology:

  • Seizures
  • Cranial nerve palsy
  • Weakness
  • Ataxia
  • Dysphasia/aphasia
25
Q

What are the CSF findings in viral encephalitis?

A

Same as menigitis

26
Q

What is the epidemiology of herpes simplex encephalitis?

A

Rare, but high mortality in untreated

Bimodal distribution:

Increased incidence 50 yrs

Equally spread between sexes: ♀=♂

27
Q

What is the pathogenesis of herpes simplex encephalitis?

A

Primary infection vs. reactivation

  • Direct transmission of the virus along neural/olfactory pathways
  • Or reactivation in the trigeminal ganglia

Acute focal necrotising encephalitis

Inflammation / swelling of brain tissue

28
Q

What treatment is given in herpes simplex encephalitis?

A

High dose IV aciclovir

  • 10mg/kg tds
  • 14-21 days
  • Start on clinical suspicion (do not wait for CSF results – it is a medical emergency)

Oral switch not recommended

Insufficient evidence to recommend steroids

29
Q

What is acute disseminated encephalomyelopathy (ADEM)?

A

Immune-mediated CNS demyelination

Can follow viral illness or vaccination (e.g. influenza)

Clinical features same as encephalitis

CSF findings = viral meningitis.

MRI helpful.

Treatment is steroids/other immunosuppressants

Recovery variable

Clinical Pathology (65 decks)

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