How Much Cerebrospinal Fluid Should We Remove Prior to Measuring a Closing Pressure?

OBJECTIVE: The objective of this study was to identify a relationship between cerebrospinal fluid (CSF) volume removal and change in CSF pressure in children with suspected idiopathic intracranial hypertension (IIH).

METHODS: We performed a cross-sectional study of children 22 years and younger who underwent a lumbar puncture (LP) and had a documented opening pressure, closing pressure, and volume removed. Relationship between volume removal and pressure change was determined using a fractional polynomial regression procedure.

RESULTS: In the 297 patients who met the inclusion criteria, CSF pressure decreased by 1 cm H2 O for every 0.91 mL of CSF removed if the maximum change in pressure was less than 15 cm H2 O ( R2 = 0.38).

CONCLUSION: A linear relationship exists between the volume of CSF removed and the amount of pressure relieved when the desired pressure change is less than 15 cm H2 O.