Differences between forms of meningitis in HIV infection
Feature
Pyogenic
Tuberculous
Cryptococcal
Symptom duration
Hours to days
Days to weeks
Days to weeks
Headache
Usually
Usually but not invariable
Usually but not invariable
Neck stiffness
Variable
Variable
Usually absent (80%)
Fever
Usually
Variable
Variable
Chest signs (and CXR)
Rare
May have features of pulmonary TB Usually normal, but cryptococcal
pulmonary disease possible
CSF opening pressure
Variable
Often raised, but an unreliable differentiator
CSF glucose
Low
Usually low
CSF protein
Usually modestly elevated Often markedly elevated
May be normal, but usually mildly
elevated
Cell count
Usually moderately or
extremely elevated
Normal in about one third of
patients
Lymphocyte/neutrophil
ratio
Predominantly neutrophils Lymphocytes but may have an early If any cells, usually lymphocytes
neutrophil predominance
Gram stain
May show organisms
Negative
Negative; sometimes reported as
‘fungal elements present’
Indian ink
Negative
Negative
Usually but not always positive
Cryptococcal CSF antigen Negative
test
Negative
Usually but not always positive
(sensitivity 90–100%)
CSF culture
Often positive, but takes some
weeks
Usually unnecessary
Often informative
Usually modestly elevated
Normal in 50%
Source: Michael Eddleston / Robert Davidson / Andrew Brent / Robert Wilkinson (2008): Oxford Handbook of Tropical Medicine.
3rd ed., Oxford University Press
CSF indices in cerebral infections of different aetiology
Cause
Normal CSF
Pyogenic
bacteria
TB
PAM
Virus
Cryptococcus
Appearance
Clear and
colourless
Cloudy or
purulent
Clear, yellowish,
slightly cloudy
Clear or slightly Clear
cloudy
Clear or slightly
cloudy
White cells
(majority)
<5/mm3
>10/mm3
>10/mm3
>200/mm3
>10/mm3 >200/mm3
Glucose
2.5–4 mmol/l
(45–72 mg%)
Markedly ↓ or Low
absent
Normal or
slightly ↓
Normal
Low
Total protein
0.15–0.4 g/l
Raised
Raised
Normal or
slightly ↓
Raised
Raised
Microscopy
None
Gram: pus
Ziehl–Neelsen:
AFB present
Wet: motile
amoebae
None
India ink +ve
Source: Michael Eddleston / Robert Davidson / Andrew Brent / Robert Wilkinson (2008): Oxford Handbook of Tropical Medicine.
3rd ed., Oxford University Press