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Module 3C - Neuro / Ophthal > Lumbar puncture (CSF) results interp. > Flashcards

Lumbar puncture (CSF) results interp. Flashcards

1
Q

Indications for lumbar puncture

A
  • Suspected CNS infections (eg. meningitis)
  • Subarachnoid haemorrhage
  • Relieve CSF pressure and confirm IIH
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2
Q

Contraindications for lumbar puncture

A
  • Raised ICP signs - papilloedema OR space-occupying lesion (Ct head to rule out first)
  • Altered mental status
  • Active seizure/post-ictal
  • Haemodynamically unstable
  • Immunocompromised
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3
Q

Normal CSF values:

  • Appearance:
  • WBC:
  • RBC:
  • Protein:
  • Glucose:
  • Opening pressure:
A
  • Appearance: clear and colourless
  • WBC: 0-5 cells/µL (only lymphocytes)
  • RBC: 0-5 cells/µL
  • Protein: 0.15-0.45g/L
  • Glucose: 2.8-4.2 mmol/L (or > 60% serum glucose conc.)
  • Opening pressure: 10–20 cmH₂O
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4
Q

CSF findings in bacterial meningitis:

  • Appearance:
  • WBC:
  • Protein:
  • Glucose:
  • Opening pressure:
A
  • Appearance: cloudy
  • WBC: elevated (PMNs - neutrophils)
  • Protein: elevated (> 1)
  • Glucose: low CSF to serum ratio (< 40%)
  • Opening pressure: high
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5
Q

CSF findings in viral meningitis:

  • Appearance:
  • WBC:
  • Protein:
  • Glucose:
  • Opening pressure:
A
  • Appearance: clear
  • WBC: elevated (lymphocytes)
  • Protein: normal
  • Glucose: normal CSF glucose to serum glucose ratio
  • Opening pressure: normal / slightly elevated
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6
Q

CSF findings in TB meningitis:

  • Appearance:
  • WBC:
  • Protein:
  • Glucose:
  • Opening pressure:
A
  • Appearance: opaque (if left to settle it forms a fibrin web)
  • WBC: elevated (lymphocytes)
  • Protein: elevated (1-5)
  • Glucose: low CSF to serum ratio (< 40%)
  • Opening pressure: high
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7
Q

CSF findings in fungal meningitis:

  • Appearance:
  • WBC:
  • Protein:
  • Glucose:
  • Opening pressure:
A
  • Appearance: clear or cloudy
  • WBC: elevated
  • Protein: high
  • Glucose: low
  • Opening pressure: high
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8
Q

CSF findings in subarachnoid haemorrhage:

  • Appearance:
  • WBC:
  • RBC:
  • Protein:
  • Glucose:
  • Opening pressure:
A
  • Appearance: blood-stained initially –> xanthochromia (yellow-ish) >12hrs later
  • WBC: elevated
  • RBC: elevated
  • Protein: elevated
  • Glucose: normal
  • Opening pressure: high
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9
Q

CSF findings in Multiple Sclerosis:

  • Appearance:
  • WBC:
  • Protein:
  • Glucose:
  • Opening pressure:
  • CSF electrophoresis:
A
  • Appearance: clear
  • WBC: slightly elevated (lymphocytes)
  • Protein: normal
  • Glucose: normal
  • Opening pressure: normal
  • CSF electrophoresis: oligoclonal IgG bands
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10
Q

CSF findings in Guillain Barre:

  • Appearance:
  • WBC:
  • Protein:
  • Glucose:
  • Opening pressure:
A
  • Appearance: clear
  • WBC: normal
  • Protein: raised (>2)
  • Glucose: normal
  • Opening pressure: normal or slightly high (if very high protein)
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11
Q

CSF interp.
.
A 28-year-old man presents with a 12-hour history of high fever, severe headache, confusion, photophobia and neck stiffness. He has no significant past medical history and takes no regular medication. He is drowsy and looks unwell.
.
CSF results:
- Appearance: cloudy

  • WBC: 936 cells/µL (>95% PMN cells)
  • Protein: 3 g/L
  • Glucose: CSF:serum glucose ratio <40%
  • Opening pressure: 30 cmH2O
A

Bacterial meningitis

  • treat empirically whilst culture results are awaited
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12
Q

CSF interp.
.
A 38-year-old woman presents with 24 hours of headache, photophobia, mild neck stiffness, and coryzal symptoms. She is fully orientated, and her observations are stable.
.
CSF results:
- Appearance: clear

  • WBC: 150 cells/µL (predominantly lymphocytes)
  • Protein: 0.9 g/L
  • Glucose: normal
  • Opening pressure: 23 cmH2O
A

Viral meningitis

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13
Q

CSF interp.
.
A 52-year-old man presents with a sudden onset severe headache. The headache started 14 hours ago. Since the headache, he has felt nauseated. He is otherwise well and fully orientated. Clinical examination is largely unremarkable, but he does appear to have some mild neck stiffness.
.
CSF results:
- Appearance: yellowish

  • WBC: normal
  • RBC: raised
  • Protein: 0.80 g/L
  • Glucose: normal
  • Opening pressure: 23 cmH2O
  • Xanthochromia: positive
A

Subarachnoid haemorrhage (SAH)

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14
Q

What is xanthochromia?

A
  • yellow discolouration of CSF caused by the presence of bilirubin
  • LP must be performed >12hrs to assess for xanthochromia - RBCs broken down, releasing haem (O₂-carrying molecule) which is further metabolised by enzymes in CSF to form bilirubin
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15
Q

Gram staining in bacterial meningitis:

  • Neisseria meningitidis
  • Strep. pneumoniae
  • Listeria meningitidis
A
  • Neisseria meningitidis: gram -ve diplococci
  • Strep. pneumoniae: gram +ve diplococci
  • Listeria meningitidis: gram +ve rods/coccobacilli
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16
Q

Common causative organisms in viral meningitis

A
  • Herpes viruses - HSV / VZV
  • Enteroviruses
17
Q

Diagnostic test for viral meningitis

A

CSF viral PCR

18
Q

Diagnostic test for TB meningitis

A

acid-fast bacilli smear/culture + TB PCR

Module 3C - Neuro / Ophthal (14 decks)

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