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University of Groningen

Hydrocephalus shunts Metzemaekers, Joannes Dionysius Maria

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HYDROCEPHALUS SHUNTS

A clinical and laboratory study

This study was financially supported by grants from: Het Van Leersumfonds, Biomedic, Codman, Cordis and Promedics.

Hydrocephalus shunts. A clinical and laboratory study. Jan D.M. Metzemaekers, Groningen Thesis University Groningen

ISBN 90-367-0975-x NUGI 743

© Copyright 1998 by Jan D.M. Metzemaekers, Groningen All rights reserved. No part of this book may be reproduced in any form or by any electronic or mechanical means, including information storage and retrieval systems, without permission in writ- ing from the publisher.

Typesetting : COMPUTEKST grafische tekstverwerking, Groningen Phototypesetting : PEACH belichtingsstudio bv, Groningen Printing : Dijkhuizen Van Zanten bv, Groningen

II

RIJKSUNIVERSITEIT GRONINGEN

HYDROCEPHALUS SHUNTS

A CLINICAL AND LABORATORY STUDY

Proefschrift

ter verkrijging van het doctoraat in de Medische Wetenschappen

aan de Rijksuniversiteit Groningen op gezag van de Rector Magnificus Dr. D.F.J. Bosscher

in het openbaar te verdedigen op woensdag 30 september 1998

om 14 .45 uur

door

Joannes Dionysius Maria Metzemaekers

geboren op 14 november 1957 te Breda

Promotores Prof. dr. J.J.A. Mooij Prof. dr. J.W.F. Beks Prof. dr. K.G. Go

Referent Dr. Ir. H.L. Journée

Promotiecommissie Prof. dr. D.A. Bosch Prof. dr. J.H.A. De Keyser Prof. dr. R.P. Zwierstra

Paranimfen Monique Metzemaekers & Maarten Coppes

Contents

Chapter 1 General introduction page 1.1 Introduction 1 1.2 History of the surgical treatment for hydrocephalus 2

Chapter 2 Clinical study on hydrocephalus shunts 4 2.1 General data 4 2.1.1 Patients and data collection 4 2.1.2 Etiology of hydrocephalus and most prevalent pre-operative symptoms 4 2.1.3 Surgical procedure 4 2.1.3.1 Surgeon 4 2.1.3.2 Duration of operative procedure 5 2.1.3.3 Drainage route 6 2.1.3.4 Peri-operative antibiotics 6 2.1.4 Shunt systems 6 2.1.4.1 Valves 6 2.1.4.2 Shunt components 6 2.1.5 Pre-operative external ventricular drainage 6 2.1.6 Cerebrospinal fluid analysis 6 2.1.7 Statistical analysis 8

2.2 Results 8 2.2.1 Number of revisions and interval until revision 8 2.2.2 Causes of shunt dysfunction 8 2.2.2.1 Proximal dysfunction 8 2.2.2.2 Valve dysfunction 9 2.2.2.3 Distal dysfunction 9 2.2.2.4 Infection 9 2.2.2.4.1 Definition of infection 9 2.2.2.4.2 Epidemiology of infection 10 2.2.2.4.3 Treatment of infection 11 2.2.2.4.4 Peri-operative antibiotics and infection 11 2.2.3 Revisions and etiology of hydrocephalus 11 2.2.4 Surgical procedure and revision rate 12 2.2.4.1 Surgeon 12 2.2.4.2 Duration of operative procedure 12 2.2.4.3 Drainage route 12 2.2.5 Shunt system and first revision 12 2.2.5.1 Valves 12 2.2.5.2 Shunt components 14 2.2.6 CSF composition and revision 15 2.2.7 Morbidity 16 2.2.8 Mortality 16

VII

2.3 Discussion 18 2.3.1 Shunt revision rate per patient 19 2.3.2 Causes of shunt dysfunction 19 2.3.2.1 Proximal dysfunction 19 2.3.2.2 Valve dysfunction 20 2.3.2.3 Distal dysfunction 20 2.3.2.4 Infection 20 2.3.2.4.1 Infection and epidemiology 20 2.3.2.4.2 Treatment of infection 21 2.3.2.4.3 Prevention of infection 22 2.3.3 Revisions in various age groups 23 2.3.4 Revisions related to underlying etiology of hydrocephalus 23 2.3.5 Operative procedure and incidence of shunt revisions 24 2.3.5.1 Surgeon 24 2.3.5.2 Duration of the surgical procedure 24 2.3.5.3 Drainage route 24 2.3.6 Shunt system versus revision 24 2.3.6.1 Valves 24 2.3.6.2 Shunt components 26 2.3.7 Cerebrospinal fluid composition versus revision operations 27 2.3.8 Morbidity 27 2.3.9 Mortality 28

2.4 Conclusions 29 2.4.1 Summary of previous conclusions 29

2.5 Future directions 30

Chapter 3 Cerebrospinal fluid dynamics and hydrocephalus shunts 31 3.1 Cerebrospinal fluid dynamics 31 3.1.1 CSF flow and production 31 3.1.2 CSF absorption 32 3.1.3 CSF composition 32 3.1.4 Pressure in CSF and other compartments 33

3.2 Pressure, resistance and flow in a shunt system 34 3.2.1 Pressure 34 3.2.2 Flow 35 3.2.3 Resistance 35 3.2.3 Viscosity 35 3.2.4 Siphoning 36 3.2.5 Measuring flow in shunt systems 36

3.3 Shunt materials 37

VIII

3.4 Valve mechanics and valve types 38 3.4.1 Valve mechanics 38 3.4.2 Valve types most commonly used in our clinical study 40

3.5 Protein concentration and shunt functioning 41

3.6 Blood and shunt functioning 43

Chapter 4 Laboratory study on hydrocephalus shunt valves 44 4.1 Valve testing in a laboratory setting 44 4.1.1 Methods and materials 44 4.1.1.1 Tested valves 44 4.1.1.2 Pump-driven versus pressure-driven test rigs 46 4.1.1.3 Conditions for in vitro testing of shunt valves 46 4.1.1.4 Test rig set-up 47 4.1.1.5 Flow generator 48 4.1.1.6 Pressure modulation unit 48 4.1.1.7 Pressure measurements 50 4.1.1.8 Flow resistance devices 50 4.1.1.9 Prevention of air bubbles 51 4.1.1.10 Composition of test solutions 51 4.1.1.11 Recording protocol 51 4.1.1.12 Data-processing 53 4.1.2 Results 54 4.1.2.1 Valves 54 4.1.2.2 Pressure diagrams per valve type 54 4.1.2.3 Results per valve 55 4.1.2.4 Dynamical properties 57

4.2 Discussion 62 4.2.1 Summary of test results 62 4.2.2 Performance (saline) compared to the manufacturer’s specifications 64 4.2.3 Effect of protein on valve performance 65 4.2.4 Effect of red blood cells on valve functioning 65 4.2.5 Opening characteristics 66 4.2.6 Closing characteristics 66 4.2.7 Effect of modulation 67 4.2.8 Concluding remarks 68

4.3 Conclusions 69

Chapter 5 General discussion 70 5.1 Comparison between clinical and laboratory results 70

5.2 Future recommendations 71

IX

Appendix A Pressure diagrams per valve 75

Appendix B Dynamical characteristics 83

Summary 91

Samenvatting 95

References 99

Nawoord 105

Curriculum Vitae 107

X

Chapter 1 General introduction

1.1 Introduction

In the Netherlands, about 650 cerebrospinal fluid (CSF) shunt insertions for hydrocepha- lus and about 500 shunt revisions take place each year127. Therefore, the treatment of hydrocephalus consitutes an important part of the neurosurgical practice. At the begin- ning of this study there was a meeting of Dutch Neurosurgeons, where it became clear that there was hardly any communication between surgeons about the treatment of hydro- cephalus. There was no clear overview of the shunt systems that were used and the com- plications that occurred. The choice for a certain system was based on remarks such as: ‘this system is easy to work with’ and ‘I hardly see any complications of this system in practice’. Furthermore, there was no consensus on the surgical technique and the implica- tions of raised protein and erythrocyte concentrations in the CSF. The need for a multi- centre clinical study on the functioning of CSF shunts was obvious.

From December 1989 until January 1992 data were collected on 400 patients undergo- ing primary shunt insertions for hydrocephalus. These patients were recruted from eight neurosurgical centres. The follow-up period of these patients was at least two and a half years. Next to this clinical study, a laboratory study was conducted in which the eight most frequently inserted hydrocephalus valves from the clinical study were tested in several ways.

The aim of the study is: * to give an overview of shunt systems used in Dutch neurosurgery and their concomi-

tant complications * to show if increased protein or erythrocyte concentrations in a laboratory setting

impair valve performance compared to the performance during perfusion with saline, and, to compare the results of saline perfusion with the manufacturer’s specifications.

* to find a correlation between the properties of the valve as found in the laboratory and the behavior of the valves in clinical practice.

1

1.2 His