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neurology > CNS Infection > Flashcards

CNS Infection Flashcards

1
Q

What types of CNS infection are there?

A
  • Acute pyogenic (bacterial) meningitis
  • Acute aseptic (viral) meningitis
  • acute focal suppurative infection (brain abscess, subdural/extradural empyema)
  • Chronic bacterial infection (TB)
  • Acute encephalitis (infection of brain parenchyma)
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2
Q

What viruses tend to cause viral meningitis?

A

Enteroviruses e.g. ECHO virus

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3
Q

How is viral meningitis managed?

A

Usually supportive treatment as illness is self-limiting

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4
Q

Give 2 common causes of viral encephalitis, and how they are treated.

A

Herpes simplex
Varicella zoster
Both treated with high dose aciclovir (IV for HSV) - this should be given asap (give empirically if delay of >6 hours for investigations is expected)

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5
Q

What are the clinical features of encephalitis?

A
  • Usually insidious onset
  • Meningismus
  • stupor, coma
  • seizures
  • partial paralysis
  • Confusion, psychosis
  • speech, memory symptoms
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6
Q

What are the common causes of bacterial meningitis in neonates?

A

Group B strep - if within 24 hours of birth this is most likely cause (from maternal vaginal flora)
Listeria
E.coli

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7
Q

What are the common causes of bacterial meningitis in adults?

A

10-21: meningococcal
>21: pneumococcal > meningococcal
Elderly: pneumococcal > listeria

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8
Q

What are the clinical contraindications to lumbar puncture without neuro-imaging?

A
  • Moderate - severe impairment of consciousness (reduced or fluctuating GCS 2)
  • Focal neurological signs (e.g. poorly responsive pupils)
  • Abnormal posture/posturing
  • Papilloedema
  • After seizures, until stabilised
  • Relative bradycardia with hypertension
  • immunocompromise
  • systemic shock
  • Coagulation abnormalities (low platelets or anticoagulant drugs)
  • local infection at lumbar puncture site
  • suspected meningococcal septicaemia
  • respiratory insufficiency
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9
Q

Name a source of listeria infection in meningitis.

A

Eating soft cheese

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10
Q

A patient presents with fever, confusion and meningism. They have been in hospital due to a fractured cribriform plate. You suspect meningitis. What are the most likely infective organisms?

A

Pneumococcus
Haemophilus influenzae
Group A beta-haemolytic strep

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11
Q

In bacterial meningitis, what organisms are associated with neurosurgery or open head trauma?

A

Staph aureus
Staph epidermidis
Gram negative rods

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12
Q

You suspect bacterial meningitis in a patient with a CSF shunt. What are the most likely infective organisms?

A

Staph epidermidis
staph aureus
aerobic gram negative rods
proprionobacterium acnes

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13
Q

What are the 3 mechanisms associated with the pathogenesis of bacterial meningitis?

A
  1. Nasopharyngeal colonisation
  2. direct extension of bacteria
    - mastoiditis, sinusitis, brain abscess
    - across skull fracture/defect
  3. from remote foci of infection e.g. endocarditis, pneumonia
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14
Q

What causes the symptoms in meningococcal meningitis?

A

endotoxin production

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15
Q

Name 3 causes of bacterial meningitis that commonly colonise the throat/nasopharynx of healthy individuals.

A

Neisseria meningitidis
Haemophilus influenzae
Strep pneumoniae

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16
Q

What organism causing meningitis are hospitalised patients, CSF skull fractures, diabetics, alcoholics, and young children most susceptible to?

A

Strep pneumoniae

17
Q

What does Listeria monocytogenes look like on Gram stain?

A

Gram positive bacilli

18
Q

What antibiotic treats Listeria meningitis?

A

IV amoxicillin (or ampicillin)

19
Q

What are the clinical signs and symptoms of bacterial meningitis?

A 
Fever
Neck stiffness
Altered consciousness
Headache
Vomiting
Pyrexia
Photophobia
Lethargy
Confusion
Rash
20
Q

What are the investigations for diagnosing bacterial meningitis?

A 
Blood cultures
CSF:
- culture and microscopy
- biochemistry for glucose and protein
- blood count and antigen detection
- PCR
Throat swab
21
Q

What are the CSF findings in aseptic (non-pyogenic) meningitis?

A

Low WCC
Minimally elevated protein
Normal glucose

22
Q

How should patient with acute bacterial meningitis be managed?

A
  • Blood cultures and throat swab
  • If no contraindications - LP
  • Start empirical abx: Ceftriaxone 2g IV (cefataxime) - DO NOT WAIT FOR LP RESULTS
  • If delay in LP >30 minutes, start empirical abs first
  • steroids: dexamethasone with or just before first dose of abx
  • tailor abx treatment once you get LP results
  • If signs of raised ICP, do not do lumbar puncture
  • Start empirical abx: Ceftriaxone 2g IV
  • steroids
  • CT head
  • manage in critical care unit

For all patients - notify public health and give abx prophylaxis to patient contacts

23
Q

What is the empiric antibiotic therapy used in bacterial meningitis?

A

IV Ceftriaxone 2g bd
Add IV amoxicillin 2g ads if listeria suspected (age >55)

If penicillin allergy:

  • IV chloramphenicol and IV vancomycin
  • Co-trimoxazole if listeria suspected
24
Q

What antibiotics are used in the contact prophylaxis regimen for bacterial meningitis?

A 
Adults and children >12:
- Rifampicin - oral, 600mg, 4 doses
- Ciprofloxacin - oral, 500mg, single dose
- Ceftriaxone - IM, 250mg, single dose
Children

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