Childs Nerv Syst (2005) 21: 524–527DOI 10.1007/s00381-005-1219-0 PRESIDENTIAL ADDRESS

Marion Walker

Published online: 30 June 2005# Springer-Verlag 2005

Looking at hydrocephalus: where are we now,where are we going?

M. Walker (*)Primary Children’s Medical Center, University of Utah,100 North Medical Drive, Suite 2400,Salt Lake City, UT, 84113, USAe-mail: marion.walker@hsc.utah.edu

Introduction

It is an honor and my pleasure to stand before you today asthe President of the International Society for PediatricNeurosurgery (ISPN). I have had the honor of serving invarious capacities within the ISPN organization. It has beena pleasure to get to know so many of my colleagues fromaround the world who have a passion for and a desire toimprove the status of neurosurgery for children. I began thepractice of pediatric neurosurgery in 1976 at the PrimaryChildren’s Medical Center in Salt Lake City, UT. At thattime, there were very few young neurosurgeons who werechoosing to specialize in pediatric neurosurgery. Our sub-specialty was in its infancy. Thanks to the inspiration frommany of our early pioneers, including Donald Madsen,Bruce Hendrick, AnthonyRaimondi, and RobertMcLaurin,it was an easy decision for me to limit my practice tochildren. The opportunity for me to spend a year at theHospital for Sick Children from July 1972 through June1973 with Bruce Hendrick, Harold Hoffman, and RobinHumphreys truly inspired me. I came away from that yearknowing that pediatric neurosurgery would be my careerpath.

The identification of pediatric neurosurgery as a sub-specialty within neurosurgery has been an evolutionaryprocess over the past 30 years. In many countries around

the world pediatric neurosurgery is a recognized subspe-cialty. Most of our adult colleagues are grateful that thereare those among us who desire to specialize in children.One of the many factors that has led to the recognition ofpediatric neurosurgery has been that the neurosurgicaldisease that we see in children is different from that whichis seen by our adult counter parts.

Recognition has also come through our local, national,and international societies. We have special pediatric neu-rosurgical sections within large neurosurgical societies inmany of our various countries. In addition, we have devel-oped journals; we have special fellowship training pro-grams in pediatric neurosurgery and, in some cases, actualcertification of pediatric neurosurgeons.

Where have we come from?

Congenital malformations of the central nervous system,including spinal dysraphism, have long been recognized asrequiring special expertise in the understanding of the de-velopment of the central nervous system and the specialanatomy and pathophysiology that accompanies these dis-orders. Children born with myelomeningocele are nowroutinely expected to survive. Our ability to manage theassociated conditions has had a dramatic impact on thequality of the survival.

Craniofacial disorders have evolved into areas of spe-cial interest and we are involved in the care of these pa-tients through craniofacial teams. The outcome for thesepatients has improved significantly over the past 40 years.

The types and locations of brain tumors in children havetheir own special nuances. The treatments offered to chil-dren with brain tumors, including surgery and adjuvanttherapy, can be quite different from that given to adultneurosurgery patients. The recognition that radiotherapy isharmful to the developing brain has led to more aggressivesurgical approaches and less aggressive radiotherapy inchildren. Even the expected outcome from malignant tu-

mors in children is much more hopeful than that associatedwith the common malignancies seen in adult neurosurgerypatients. Pediatric neurosurgeons have been involved withtheir pediatric oncology colleagues for many years in thedevelopment of treatment protocols that have proven to bevery effective with certain tumors. The outcome from me-dulloblastoma in children is dramatically better than what itwas when I began my practice of pediatric neurosurgery in1976.

Even trauma is different in children. The types of in-juries and the outcome from injury are dramatically differ-ent in the pediatric patient as compared with the nature ofinjuries sustained in the adult population. We have a muchbetter understanding of the deleterious effects of intracra-nial pressure and have improving methods to treat it. Pe-diatric intensive care units help us in the management ofpediatric trauma. We understand the importance of docu-menting and treating the effects of the long-term sequelaeof head injuries.

Where do we go from here?

Our progress in treating these various conditions has beendramatic in my lifetime. However, hydrocephalus remainsas one condition with which we seem to have made verylittle progress over the past 50 years. There is no questionthat shunts save lives. The arrival of the ability to treathydrocephalus with valved shunt systems revolutionizedthe treatment of hydrocephalus, but the long-term outcomefrom shunting is very similar to that seen in 1960. How-ever, our focus seems to be on the valvular control ofcerebrospinal fluid (CSF) flow and less on the correction ofthe underlying pathophysiology of hydrocephalus. It isalmost as if research into the basic pathophysiology ofhydrocephalus and the search for other options for treat-ment stopped with the advent of the shunt.

The landmark shunt design trial by Drake and Kestle[1] shows us that at 1 year approximately 60% of newlyshunted patients will still have a functioning shunt and at2 years approximately 40% of the patients will have nothad a revision. I feel there are options that we should con-sider when considering the long-term effects of shuntingfor hydrocephalus, especially if the shunt is placed ininfancy. I would like to address the remainder of my re-marks to some of the thoughts that I have regarding thepathophysiology of the long-term consequences of shunt-ing. I will give some of my thoughts about the directionthat I think we should be headed in the management ofhydrocephalus.

Shunt overdrainage is a significant issue for a large por-tion of children shunted in infancy. Essentially all shuntstend to overdrain. Overdrainage can be manifested in sev-eral ways, including the development of extra axial fluidcollections and/or the development of slit ventricles andsensitivity to low intracranial pressure or intermittent shunt

malfunction. When a shunt is placed in infancy and itslowly drains an excessive amount of CSF, the rapidlygrowing brain during the first two years of life begins to fillthe intracranial space. After a relatively short period thepatient has developed a fixed skull filled with brain pa-renchyma, blood, meninges, and vasculature, with onlysmall amounts of CSF remaining in the intracranial space(Fig. 1). As the intracranial volume of CSF becomes di-minished, there is a loss of normal intracranial compensa-tory mechanisms. Slitlike ventricles leave little room forcompensation seen in an otherwise normal intracranialspace. Associated with this is the finding that the occip-itofrontal circumference (OFC) of the growing child beginsto fall more toward the bottom side of the head circum-ference growth chart as compared to normal. The normalintracranial pulsations seen with each heartbeat are di-minished in patients with shunted hydrocephalus and thestimulus for head growth may also be significantly di-minished (Fig. 2). It is an interesting phenomenon that theslit ventricle syndrome (SVS) occurs only in children. Ittends to occur only in children shunted in infancy whodevelop the pathophysiology necessary to lead to the prob-lems associated with the slitlike ventricles. Adults do notget SVS. They can get small ventricles, but when hydro-cephalus occurs after the skull is fully grown and once thebrain has reached its adult size there does not develop adisproportion between the size of the skull and the brain. Itis true that adults can have some of the problems associatedwith small ventricles but they do not develop the full-blown slit ventricle syndrome that we see in children.

Slit ventricle syndrome has been defined as the inter-mittent symptoms of shunt malfunction in a child that ap-pears otherwise healthy. It is associated with headache,varying degrees of lethargy, and may or may not be as-sociated with nausea and vomiting. The differential diag-nosis of SVS includes low-pressure syndromes, symptoms

Fig. 1 Computed tomography scan of a patient with slit ventricles.There appears to be no room for normal compensatory mechanisms

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of intermittent obstruction, and can even include cerebralvasomotor instability.

The incidence of SVS is not well known. The perceivedincidence of SVS will depend on the definition and howclosely patients are followed for possible signs and symp-toms. Based on a study by Walker et al. [2], the incidenceof SVS in 270 patients shunted in infancy was 64%. Ninepercent of the patients had normal ventricles, 9% hadslightly enlarged ventricles, and 18% had markedly en-larged ventricles.

The treatment of SVS has varied. There are so manyoptions for treatment that it would suggest that we have notfound an optimal therapy (Table 1). Even when we con-sider shunt revision alone there are various options that canbe tried. Occasionally, the ventricular catheter is revisedwithout other portions of the shunt being changed. Therecan be a valve upgrade; there can be placement of a flowcontrol device, revision of both the valve and the placementof a flow control device, and now the possibility of using aprogrammable shunt with or without flow control.

The prevention of slit ventricles must be directed at theunderlying cause. It is my belief that treatment must beginearly. Prevention appears to be the only likely treatmentthat we have for the near future. For the child that grows

up with a very tight intracranial space it may be too lateto change the pathophysiology for what has developedthrough time. Trying to change the intracranial compli-ance in a patient that has had a tight intracranial space for10–15 years may be a very difficult task. It intuitivelymakes more sense to try and prevent the developmentof this abnormal intracranial pathophysiology at earlierstages.

How could we prevent the slit ventricles? We should tryto delay the development of small ventricles as long aspossible. If a patient who is shunted in adulthood does notdevelop SVS and a patient shunted in infancy does, thenwhere along the growth curve is there a change? We have

Fig. 2 A typical growth curvefor a patient shunted in infancy.The OFC starts off above the95th percentile curve but slowlybecomes closer to the 5th per-centile as the shunt systemdrains. This phenomenon isfound only in children shuntedin infancy

Table 1 Treatment options for slit ventricle syndrome

ObservationAntimigrainous therapyShunt revisionLimit over drainage (flow control, antisiphon)ICP monitoringSubtemporal decompressionCranial morcellationThird ventriculostomy

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approximately 80% of our brain growth by 2 years of age.What happens if the first shunt is placed at 2 years ratherthan in infancy? Is there development of a slit ventriclepicture with abnormal intracranial pathophysiology if achild is shunted at 5, 10, or 15 years of age? Where alongthe growth curve could we expect to see a change? We donot know the answers to these questions.

Do programmable valves have a place in the manage-ment of hydrocephalus in infants? It could be that if wewere to gradually increase the ventricular pressure as theventricles decrease in size after initial shunting that wemight be able to extend the time before the development ofslit ventricles. This might pay huge dividends as the childgrows. This remains an unanswered question but onewhich I believe we must study.

Conclusions

Pediatric neurosurgery has emerged as a viable subspe-cialty within neurosurgery throughout the international com-

munity. We have been very successful in our managementof many of the unique neurosurgical conditions affectingchildren. Hydrocephalus, however, remains a significantchallenge. It interfaces with almost all that we do in neu-rosurgery ranging through congenital malformation, de-velopmental disorders, brain tumors, infectious disease,and trauma. Although the treatment of hydrocephalus withvalved shunts has saved countless lives, we now must lookto the future to go beyond the mere management of ex-cessive CSF and toward a functional treatment for hydro-cephalus that addresses the underlying pathophysiology.

References

1. Drake JM, Kestle J (1996) Determining the best cerebrospinalfluid shunt valve design: the pediatric valve design trial.Neurosurgery 38(3):604–607

2. Walker M et al (1993) Diagnosis and treatment of the slit ven-tricle syndrome. In: Butler A, McLone D (eds) Neurosurgeryclinics of North America. Saunders, Philadelphia, pp 707–714

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