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Hydrocephalus
Hydrocephalus
Hugh J. L. Garton, MD, MHSc
a,
*
Joseph H. Piatt, Jr, MD, FAAP
b,c
a
Department of Neurosurgery, University of Michigan, Taubman 2128/0338,
1500 E. Medical Center Drive, Ann Arbor, MI 48105, USA
b
Section of Neurosurgery, St. Christophers Hospital for Children, Erie Avenue at Front Street,
Philadelphia, PA 19134, USA
c
Departments of Neurological Surgery and Pediatrics, Drexel University College of Medicine,
Philadelphia, PA, USA
Hydrocephalus is not an exotic condition in general pediatric practice, but data
on which to base calculations of the incidence and prevalence of hydrocephalus
are scarce. Working with the 1988 National Health Survey of United States non-
institutionalized population, Bondurant [1] estimated that there were 56,566
children 18 years or younger with a cerebrospinal fluid (CSF) shunt in place.
Taking a denominator from 1988 census data, one can calculate a prevalence of
hydrocephalus of 0.9 per 1000 children or 22.5 affected children per 100,000 total
population. Data from population-based studies in Sweden suggest the incidence
of infantile hydrocephalus rose from 0.48 per 1000 live births between 1967 and
1970 to 0.63 per 1000 live births between 1979 and 1982; the increase was
attributed to survival of premature infants with intraventricular hemorrhage (IVH)
[2]. The pediatric Shunt Design Trial, a multicenter trial conducted in North
America and Europe, enrolled only newly diagnosed patients undergoing initial
shunt insertion [3]. The condition categorized by the Swedish population-based
study as infantile hydrocephalus accounted for about half of all patients in the
Shunt Design Trial, suggesting that the overall prevalence of childhood hydro-
cephalus is about twice the Swedish incidence, in the neighborhood of 1.2 per
1000 children assuming minimal mortality after shunt placement. If an ordinary
pediatric practice carries between 2000 and 4000 patients per physician, and if
0031-3955/04/$ see front matter
D 2004 Elsevier Inc. All rights reserved.
doi:10.1016/j.pcl.2003.12.002
* Corresponding author. Department of Neurosurgery, University of Michigan, Taubman 2128/
0338, 1500 E. Medical Center Drive, Ann Arbor, MI 48105.
E-mail address: hgarton@umich.edu (H.J.L Garton).
Pediatr Clin N Am 51 (2004) 305 325 affected children are distributed uniformly among pediatric practices (probably
not a valid assumption), a general pediatrician might expect to serve 2 to 5
children with CSF shunts.
Basic physiology
Hydrocephalus is a disturbance of CSF physiology. The secretion of CSF by
the choroid plexus is a metabolically active process involving ion pumps and
enzyme systems similar to those found in the distal tubule of the kidney. CSF is
indistinguishable from brain extracellular fluid, and because water and electro-
lytes pass freely in and out of the brain across the ependymal surfaces of the
ventricular system, the brain itself is believed to be responsible for a small frac-
tion of total CSF production. CSF secretion continues at an essentially constant
rate, about 20 mL/hour in adult humans, regardless of intracranial pressure (ICP)
as long as the choroid plexus and the brain itself are perfused. Age, body mass,
and various disease states undoubtedly affect the rate of CSF secretion, but
methodologies for studying these affects in humans are problematic. Unlike CSF
secretion, CSF reabsorption is a purely passive process driven in a linear fashion
by the pressure differential between the subarachnoid space and the venous
circulation, specifically, the major dural venous sinuses within the cranial cavity.
Thus the intradural compartment does not stray far from a steady state charac-
terized by equal CSF secretion and reabsorption and ICP within the normal range.
With the rare exception of choroid plexus papilloma, a tumor of the choroid
plexus that causes excessive CSF secretion, the diseases that cause hydrocepha-
lus do so by interfering with CSF reabsorption. A higher pressure gradient is
required to drive CSF back into the venous circulation, so, although all but the
most acutely unstable patients with hydrocephalus eventually achieve a steady
state between CSF secretion and reabsorption, they do so only at an abnormally
high ICP.
Out of respect for historical tradition, hydrocephalus sometimes been charac-
terized further as either communicating or obstructive. These terms date to the era
of pneumoencephalography. If air introduced into the lumbar theca appeared
eventually within the ventricles of the brain, the ventricles and the lumbar sub-
arachnoid space were said to communicate. If air filled the dilated ventricles,
such communicating hydrocephalus was presumed to be caused by obliteration of
the subarachnoid spaces or the arachnoid granulations (the sites of CSF reab-
sorption in the dural venous sinuses) by diffuse inflammatory disease processes,
such as meningitis or subarachnoid hemorrhage. Cases of hydrocephalus in which
the ventricles could not be filled with air introduced from below were attributed
to lesions obstructing bulk flow of CSF. This dichotomy has limited useful-
ness today. Determining the category to which a patient belongs on the basis of
history, physical examination, and even noninvasive imaging studies can be dif-
ficult, as contemporary experience with endoscopic third ventriculostomy (ETV)
has shown.
H.J.L. Garton, J.H. Piatt, Jr / Pediatr Clin N Am 51 (2004) 305325
306 Causes of hydrocephalus
Hydrocephalus can present in all age groups; however, the management and
prognosis differ significantly depending on the cause and age at presentation.
Common causes for hydrocephalus are listed in Box 1.
The patterns of hydrocephalus encountered in an individual practice or at a
particular institution may vary widely depending on programmatic or referral
factors. The older literature, mostly reports of institutional experiences, cites
myelomeningocele as the leading distinct cause of childhood hydrocephalus
[4,5], but in more recent, multicenter treatment trials, posthemorrhagic hydro-
cephalus of prematurity is at least as common [3,6,7]. Posthemorrhagic hydro-
cephalus is reviewed in detail in this article. The management of the newborn
with myelomeningocele is discussed elsewhere in this volume, as is the man-
agement of antenatally diagnosed congenital hydrocephalus.
Intraventricular hemorrhage and posthemorrhagic hydrocephalus
Incidence and pathophysiology
Hydrocephalus appears most commonly in the newborn period as a result of
an IVH originating from periventricular germinal matrix. In the premature infant
in particular, the walls of blood vessels in the germinal matrix region lack certain
structural elements present in more mature vessels, and they lack substantial
Box 1. Causes of hydrocephalus
Prematurity (posthemorrhagic hydrocephalus)
Myelomeningocele
Other congenital or developmental conditions affecting the brain
Dandy-Walker malformation
Arachnoid cysts
Interhemispheric cysts
Aqueductal stenosis
Encephalocele
Brain tumor
Subarachnoid hemorrhage
Traumatic brain injury
Aneurismal subarachnoid hemorrhage
Congenital or developmental conditions affecting the skull
Crouzon, Pfeiffer syndromes
Achondroplasia
Meningitis
H.J.L. Garton, J.H. Piatt, Jr / Pediatr Clin N Am 51 (2004) 305325
307 external tissue support. They supply blood to the rapidly dividing cells of the
germinal matrix, which is the site of origin for a both neuronal and glial cells
ultimately destined for cortex. These fragile vessels are exposed to arterial and
venous hemodynamic surges in the premature infant and can rupture, usually
within the first 72 hours of life [8].
The severity of the hemorrhage is traditionally grade by Papiles criteria [9].
There are several modifications of this scale, but as reported by Whitelaw
[8], grade 1 is germinal matrix hemorrhage without extension into the ventricle,
grade 2 is IVH involving up to 50% of ventricular area and not dilating the
ventricle, and grade 3 is IVH involving greater than 50% ventricular area and
dilating the ventricle. Grade 4 is traditionally considered to have an intrapa-
renchymal component outside the germinal matrix region, although Volpe [10]
argues that intraparenchymal hemorrhage should be reported separately from the
grading of the IVH. In addition, Volpes interpretation of IVH grades does not
specifically refer to ventricular dilatation as part of the criteria, limiting consid-
eration to percentage of ventricular volume occupied by the clot.
The mechanism by which IVH leads to hydrocephalus has been conjectured
to be occlusion of the arachnoid gra