*CSF pressure ā„25cmH2O = intracranial hypertension (idiopathic, meningitis, intracranial haemorrhage, tumours etc). Up to this level may be normal due to stress/pain/anxiety. 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)
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