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Cerebrospinal fluid (CSF) interpretation [advanced]

Learn how to perform the procedure too…

Performing a lumbar puncture is covered here!

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*CSF pressure ≥25cmH2O = intracranial hypertension (idiopathic, meningitis, intracranial haemorrhage, tumours etc)
NB: in bacterial meningitis patients who have had antibiotics prior to LP, CSF may be more lymphocytic and have a normal glucose

Typical Pathogens

  • Bacteria in newborns: group B strep, E. coli/coliforms, listeria monocytogenes
  • Bacteria in young children: N. meningitidis, strep pneumonia, Haemophilus influenzae
  • Bacteria in teens/adults: strep pneumoniae, N. meningitidis, listeria monocytogenes (if >50 years/pregnant)
  • Viruses: enterovirus, VZV, HSV, HIV, mumps
  • Fungi: cryptococcus neoformans

Additional Tests

  • Culture: grow bacteria
  • PCR: for viruses e.g. enterovirus, HSV, VZV
  • Electrophoresis: oligoclonal bands (MS)
  • Acid-fast stain, TB culture and TB PCR: TB
  • Xanthochromia: subarachnoid haemorrhage
  • India ink stain and cryptococcal antigen test: cryptococcus
  • Cytology: to look for malignant cells

Causes for abnormal CSF

  • Increased neutrophils: bacterial meningitis, early TB, some viruses (e.g. enterococcus), some fungi (usually <80%), following seizures, following CNS haemorrhage, following CNS infarct, foreign materials, metastatic tumour
  • Increased lymphocytes: viral meningitis, viral encephalitis, HIV, partially treated bacterial meningitis, some bacterial meningitides (Listeria, Mycoplasma, Lyme, Syphilis), cryptococcal meningitis, TB meningitis, parasitic meningitis, parameningeal bacterial infections, others uncommon (UTI <3m old, SSPE, MS, encephalopathy due to drugs, sarcoidosis, neoplastic/paraneoplastic, vasculitis, autoimmune encephalitis, other autoimmune conditions e.g. SLE)
  • Increased eosinophils: parasitic infections (Angiostrongylus, Gnathostomiasis, Baylisascaris), fungal infections, reaction to foreign material, occasionally bacterial/TB meningitis, lymphoma, sarcoid

Adjusting for… A traumatic tap

  • Allow 1 white cell for every 1000 red cells
  • Allow 0.01g/L protein for every 1000 red cells
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