Edlow listed various changes in the cerebrospinal fluid that can help to distinguish a bloody lumbar puncture from a subarachnoid hemorrhage.
Assumption: CSF is collected in a series of tubes (3 or 4)
Parameters:
(1) opening pressure at the lumbar tap
(2) xanthochromia of the CSF
(3) findings at a repeat lumbar puncture at higher level
(4) change in RBC count between fluid tubes
(5) RBC morphology
(6) clot formation
(7) D-dimer
(8) erythrophagocytosis
Findings
Subarachnoid Hemorrhage
Traumatic Tap
opening pressure
often elevated, sometimes not
normal
xanthochromia
present
absent
repeat lumbar puncture done carefully
still bloody
often clear
change in the RBC count between tubes
none
decreases from first tube to last
RBC morphology
crenated
similar to peripheral blood
D-dimer
elevated
similar to plasma
erythrophagocytosis
present
absent
where:
• The WBC count in the CSF after a subarachnoid hemorrhage is similar to the peripheral blood early, but then tends to rise due to development of a nonseptic meningitis.
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