A novel approach to CSF pressure measurement via lumbar puncture that shortens the clinical measurement time with a high level of accuracy

Abstract

Intracranial pressure (ICP) is an important parameter in clinical management and diagnosis of several neurological diseases. ICP is indirectly measured via lumbar puncture (LP) using a spinal manometer in clinical practice. In routine measurements of cerebrospinal fluid pressure (PCSF) from lumbar region, prolonged measurement times and low accuracy are of great concern. This measurement system consists of a spinal needle used for LP and a spinal manometer to measure PCSF. In this study, the spinal needle-spinal manometer combination was modelled with a first-order differential equation and a time constant (τ ) was defined as the product of the resistance to flow of the needle with the bore area of the manometer divided by the dynamic viscosity of CSF, i.e. τ = RA/ρCSF. Each needle/manometer combination had a unique constant as a predictor of the equilibrium pressure. The fluid pressure in the manometer rose in an exponential manner which was tested in a simulated environment using 22G spinal needles namely Braun-Spinocan, Pajunk-Sprotte and M.Schilling. Curve fitting of the manometer readings were obtained with regression coefficients of R2 ≥ 0,99 to determine measurement time constants. The residual differences between predicted and true values were less than 1,18 cmH2O. For a given needle/manometer combination, time required to reach equilibrium pressure was identical for all pressure levels. PCSF measured at reduced times can easily be interpolated to their equilibrium level allowing clinicians to obtain PCSF values with high accuracy within seconds. This method can be used as an indirect estimation of ICP in routine clinical practice.