A Simple Method of Estimating Cerebrospinal Fluid Pressure During Lumbar Puncture

Abstract

It is often difficult to measure cerebrospinal fluid (CSF) pressure in children. CSF flow through a spinal needle is described by the equation: Flow = pressure/(needle constant x relative viscosity). Thus, CSF flow rate during lumbar puncture can be used to estimate CSF pressure. Because the viscosity of CSF is approximately the same as that of normal saline, 0.9% NaCl was used to model CSF flow in vitro. Flow of saline through various spinal needles was measured as pressure and temperature were varied to determine needle constants and variation in viscosity with temperature. Counting periods for which the number of drops counted equals the pressure (in centimeters of H2O) then were determined for each needle size. At patient temperatures less than 40°C, counting periods were calculated at 21, 39, and 12 seconds, for 22-gauge 1.5-inch, 22-gauge 3.5-inch, and 20-gauge 3.5-inch spinal needles, respectively. Viscosity decreased slightly above 40°C, and counting periods became 20, 37, and 11 seconds. Finally, the method was tested prospectively in 12 patients by comparing drop count (over the calculated counting period) to manometric pressure measurement. Drop counts were within 15% of manometric pressure in all patients. This method allows simple and rapid estimation of CSF pressure during lumbar puncture.

Infantile idiopathic intracranial hypertension: case report and review of the literature

“…Even if the measurement of CSF opening pressure could be an important additional diagnostic factor, actually it is not routinely performed [ 18 ]. In our case, the neurosurgeon described the opening pressure as increased on both occasions by counting the number of CSF drops flowing through the spinal needle in a specified period, as already described [ 6 , 7 ], however we do not know the precise pressure measurement. In published studies on PTCS, CSF opening pressure was not documented for all the patients, because other factors documented indirectly elevated CSF pressure (symptoms, imaging data) [ 8 , 19 ].…”

“…After the infant’s back was cleaned with antiseptic solution, 22-gauge spinal needle was inserted at the 4th lumbar space. In this case we had not the possibility to measure CSF opening pressure, anyway we used an empiric method already described in literature [ 6 , 7 ], and we observed that in 10 s the number of CSF drops flowing through the needle was higher compared to the number observed during routine procedure. After the needle was removed, the area was cleaned and a compressive medication on the needle site was performed.…”

Comparison of numerical methods for cerebrospinal fluid representation and fluid–structure interaction during transverse impact of a finite element spinal cord model

“…Arguably, the presence of the CSF layer in spinal cord FE models is crucial to obtain accurate deformation of the spinal cord, with previous research in the brain demonstrating the importance of the CSF to accurately predict neural tissue deformation. 32 CSF has been reported to behave like a Newtonian fluid with mechanical properties similar to a saline solution containing 0.9% NaCl 33 and a reported density at 37 Celsius degrees ranging from 1.0003 to 1.0007 g/ml. 34 Previous computational studies investigating spinal cord compression demonstrated that FSI modeling of the CSF using the Arbitrary Lagrangian-Eulerian (ALE) numerical approach showed good correlation with reported experimental data.…”

“…CSF has been reported to behave like a Newtonian fluid with mechanical properties similar to a saline solution containing 0.9% NaCl 33 and a reported density at 37° Celsius degrees ranging from 1.0003 to 1.0007 g/ml 34 …”

“…In the experiment, the spinal cord complex specimens were 140 mm in length. The experimental protocol stated that the natural CSF was replaced with the pseudo‐CSF (0.9% saline solution) with similar mechanical properties to the CSF 33,49 . Spinal cord complex specimens were freeze‐clamped at both ends using dry ice 48 .…”