Validation of Davson's equation in patients suffering from idiopathic normal pressure hydrocephalus.

Afroditi-Despina Lalou,Laurent Gergele,Anna Bjornson,Virginia Levrini,Zofia Czosnyka,Matthew Garnett,Eva Nabbanja,Dong-Joo Kim,Marek Czosnyka

doi:10.1007/s00701-018-3497-9

Afroditi-Despina Lalou, Laurent Gergele + Show 7 more

Open Access

https://doi.org/10.1007/s00701-018-3497-9

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Abstract

The so-called Davson's equation relates baseline intracranial pressure (ICP) to resistance to cerebrospinal fluid outflow (Rout), formation of cerebrospinal fluid (If) and sagittal sinus pressure (PSS) There is a controversy over whether this fundamental equation is applicable in patients with normal pressure hydrocephalus (NPH). We investigated the relationship between Rout and ICP and also other compensatory, clinical and demographic parameters in NPH patients. We carried out a retrospective study of 229 patients with primary NPH who had undergone constant-rate infusion studies in our hospital. Data was recorded and processed using ICM+ software. Relationships between variables were sought by calculating Pearson product correlation coefficients and p values. We found a significant, albeit weak, relationship between ICP and Rout (R = 0.17, p = 0.0049), Rout and peak-to-peak amplitude of ICP (AMP) (R = 0.27, p = 3.577e-05) and Rout and age (R = 0.16, p = 0.01306). The relationship found between ICP and Rout provides indirect evidence to support disturbed Cerebrospinal fluid circulation as a key factor in disturbed CSF dynamics in NPH. Weak correlation may indicate that other factors-variable PSS and formation of CSF outflow-contribute heavily to linear model expressed by Davson's equation.

Highlights

Normal pressure hydrocephalus (NPH) is a syndrome characterised by ventriculomegaly and the clinical triad of gait ataxia, dementia and urinary incontinence [1, 16, 24]
Despite this syndrome being first described over 50 years ago and presenting an opportunity for symptom improvement following shunt surgery, we still know little of its pathophysiology and hydrodynamics [5, 6, 24, 28]
The values calculated for resistance to cerebrospinal fluid outflow (Rout), intracranial pressure (ICP), amplitude of ICP (AMP) and age in male and female subgroups are presented in table 1 as mean values with standard errors of the mean and level of significance (p-value) when the respective groups are compared

Summary

Introduction

Normal pressure hydrocephalus (NPH) is a syndrome characterised by ventriculomegaly and the clinical triad of gait ataxia, dementia and urinary incontinence [1, 16, 24]. Despite this syndrome being first described over 50 years ago and presenting an opportunity for symptom improvement following shunt surgery (it is described as an only kind of reversible dementia), we still know little of its pathophysiology and hydrodynamics [5, 6, 24, 28]. It is thought to be due to a hydrodynamic deficit, whether this is due to “cisternal block” or aqueduct stenosis or as a problem of cerebrospinal fluid (CSF) absorption due to arachnoid cell hyperplasia and leptomeningeal fibrosis, as well as other degenerative changes, is still uncertain[4,5,6, 13, 25]

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