Cerebral Spinal Fluid Analysis… Variations with Age

CSF TubesCerebral Spinal Fluid Analysis

When evaluating a neonate for possible meningoencephalitis, we often do not rely on what the Cerebral Spinal Fluid Analysis is, because it is well known that a neonate may have normal indices yet still have a serious bacterial infection in their CSF.  But we also know that we need to consider HSV; however, in the well appearing neonate, it is difficult to decide whom to test and treat for HSV solely based on your history and physical (that is an entirely separate morsel).

Suffice it to say that the evaluation of the CSF is an important step in determining whether a child should have the CSF sent for HSV PCR and started on acyclovir.

If there is pleocytosis on their Cerebral Spinal Fluid analysis, then test and treat the patient for HSV.[1]

  • That is the rub: what marks pleocytosis in a neonate; in a child?
    • Many textbooks will have a table that describes the normal values of CSF analysis; but it is often unclear where this data comes from.
    • A recent study looked at redefining/reasserting these values in an age where testing can be done to exclude viral infections as a potential confounding factor. I will let you peruse it to determine your own sense of it’s worth, but here is the main point: [2]
      • CSF WBC counts for 0-28 day old:
        • Mean = 9
        • Median = 3
        • 95th percentile = 19
      • CSF WBC counts for 29-56 day old:
        • Mean = 3
        • Median = 2
        • 95th percentile = 9
  • These numbers approximate what some textbooks list (The Harriet Lane Handbook, Nelson’s Essentials of Pediatrics) and have variance from others (Fleisher and Ludwig’s textbook of Pediatric Emergency Medicine
  • Morals of the story:
    • CSF pleocytosis? Test and treat for HSV in neonate.
    • Normal values of WBCs in CSF vary with age (even higher in pre-term kids).
    • Before you commit a child with borderline values to acyclovir, discuss with the admitting team.

[1] Caviness, A.C., et al., Cost-effectiveness analysis of herpes simplex virus testing and treatment strategies in febrile neonates. Arch Pediatr Adolesc Med, 2008. 162(7): p. 665-74.7.Kestenbaum,

[2] L.A., et al., Defining cerebrospinal fluid white blood cell count reference values in neonates and young infants. Pediatrics. 125(2): p. 257-64.


Sean M. Fox
Sean M. Fox
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