CNS Infections - Viral Meningitis and Encephalitis (26) Flashcards

1
Q

Meningitis

A

Inflammation of meninges

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2
Q

Encephalitis

A

Inflammation of the brain

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3
Q

Meningo-encephalitis

A

Inflammation of brain and meninges

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4
Q

Aseptic meningitis WBC

A

Above 5X10^6/L in CSF (negative bacterial culture)

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5
Q

Common causes of aseptic meningitis

A

Viruses, partially treated bacterial meningitis, Listeria, TB, syphilis, malignancy, autoimmune conditions, drugs

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6
Q

Virion

A

Basic infectious particle of virus

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7
Q

Virus structure

A

Nucleic acid (DNA/RNA), capsid, lipid envelope (derived from host cell membrane), some contain other proteins/enzymes

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8
Q

What is a capsid?

A

Protein coat, made up of capsomeres (subunits)

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9
Q

Epidemiology of viral meningitis

A

Common neonates and under 5,

5-15 cases per 100,000

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10
Q

Aetiology of viral meningitis

A
  • Enteroviruses (echoviruses, coxsackie, parch, enteroviruses 70 and 71, polio)
  • Herpes virus (HSV 2), VZV, CMV, EBV, HHV6, HHV7
  • Arboviruses
  • Mumps
  • HIV
  • Adenovirus
  • Measles
  • Influenza
  • Parainfluenza type 3
  • Lymphocytic choriomeningitis virus (LCMV)
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11
Q

What’s the lead cause of viral meningitis?

A

Enteroviruses

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12
Q

What are common causes of viral meningitis?

A

Enterovirus, HSV 2, VZV, Mumps, HIV

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13
Q

What percentage of viral meningitis cause unknown?

A

35%

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14
Q

Pathogenesis of viral meningitis

A

Colonisation of mucosal surfaces, invasion of epithelial surface, replication in cells, dissemination and CNS invasion

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15
Q

How does viral meningitis dissemination into CNS?

A

Via cerebral microvascular endothelial cells, via choroid plexus epithelium, spread along olfactory nerve

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16
Q

What are symptoms in VM mainly due to?

A

Inflammatory response in CNS

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17
Q

Clinical presentation of viral meningitis

A

Fever, Meningism (headache, neck stiffness, photophobia), lethargy, myalgia, arthralgia, sore throat, rash, diarrhoea and vomiting

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18
Q

Children clinical presentation of viral meningitis

A

Neonates/infants meningeal signs absent, nuchal rigidity/neck stiffness and bulging anterior fontanelle

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19
Q

Kernig’s sign

A

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

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20
Q

Brudzinski’s sign

A

Flexing the neck causes hip and knees to flex

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21
Q

Nuchal rigidity

A

Resistance to flexion of the neck

22
Q

Investigations

A
  • Bloods (FBC, U&E, CRP, clotting, blood culture)
  • CT (raised ICP, SAH, mass lesion)
  • Indicated before LP
  • LP (MC&S, protein, glucose, viral PCR)
  • Throat swab/stool sample (enterovirus PCR)
  • Serology (Mumps, EBV/CMV, HIV)
23
Q

LP contraindications

A

If raised ICP removing CSF can cause coning (brain though the foramen magnum)

24
Q

CSF findings in viral meningitis/encephalitis

A

WBC

25
Q

Pleocytosis

A

WBC in CSF

26
Q

Treatment for viral meningitis

A

IV antibiotics (cefotaxime) if risk of bacterial, supportive therapy, notify public health

27
Q

When do you get epidemics of enteroviral meningitis?

A

Summer/autumn epidemics

28
Q

Symptoms of enteroviral meningitis

A

Fever, vomiting, anorexia, rash, upper resp tract symptoms

29
Q

HSV 1 causes

A

Cold sores and viral encephalitis

30
Q

HSV2 causes

A

Genital herpes and meningitis

31
Q

Mollaret’s meningitis

A

Recurrent aseptic meningitis, common cause HSV2

32
Q

Primary VZV

A

Varicella - chickenpox

33
Q

Secondary VZV

A

Zoster - shingles

34
Q

Is meningitis common with VZV?

A

No, it’s unusual, can occur during/on its own/after vaccination - rash

35
Q

Mumps meningitis

A

10-30% mumps cases

36
Q

Symptoms of mumps meningitis

A

CNS symptoms 5 days after onset of parotitis (parotid gland inflammation), ab pain, orchitis

37
Q

HIV and meningitis

A

Can occur as part of primary infection

38
Q

HIV and meningitis symptoms

A

(Glandular fever), fever, lymphadenopathy, pharyngitis, rash (self-limiting)

39
Q

Aetiology of viral encephalitis

A
  • HSV 1, VZV, EBV, CMV
  • Adenovirus
  • Measles
  • Mumps
  • Enterovirus (polio)
  • Arboviruses (West Nile, Japanese B, St Louis, Eastern and Western Equine Encephalitis)
  • Influenza
  • Rubella
  • HIV
  • Rabies
  • Bacteria (Step pneumonia, Neisseria meningitidis, TB)
  • Malignancy (paraneoplastic)
  • Autoimmune
  • Acute disseminated encephalomyopathy (ADEM)
40
Q

What are the common causes of viral encephalitis?

A

HSV1, VZV, EBV, Measles, Mumps, Enterovirus, Bacteria, ADEM

41
Q

What is the most common cause of viral encephalitis?

A

HSV1

42
Q

What percentage is aetiology unknown in viral encephalitis?

A

37%

43
Q

Clinical presentation of viral encephalitis

A

Altered mental state (confusion/bizarre behaviour/coma), fever, headache, meningism?, seizures, weakness, dysphasia/aphasia, cranial nerve palsy, ataxia

44
Q

Investigations

A
  • Bloods (FBC, U&E, CRP, clotting, cultures, serology)
  • CT (before LP)
  • MRI (HSV changes)
  • LP (M, C&S, protein/glucose, viral PCR)
  • EEG (HSV abnormal temporal lobe activity)
45
Q

Treatment of viral encephalitis

A

High dose IV aciclovir

46
Q

HSE epidemiology

A

Rare, 50yrs, male=female

47
Q

HSE pathogenesis

A

Primary infection vs reaction (direct transmission of the virus along neural/olfactory pathways, reactivation in trigeminal ganglia), acute focal necrotising encephalitis, inflammation/swelling of brain tissue

48
Q

Herpes Simplex Encephalitis outcome

A

Untreated 70% mortality, treated remains high 28% at 18 months,
Paralysis, speech loss, personality change

49
Q

Acute disseminated encephalomyelopathy

A

Immune-mediated CNS demyelination, can follow viral illness/vaccination, CSF findings= viral meningitis, MRI helpful, treatment - steroids/immunosuppressants

50
Q

If an doubt on diagnosis

A

Treat as bacteria - antibiotics!