Cerebrospinal fluid (CSF) interpretation [advanced]

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