Pediatric emergency medicine trisk 1003

Goals of Treatment
Hydrocephalus can present in an acute or subacute fashion. Most children
with hydrocephalus will need surgical treatment.
CLINICAL PEARLS AND PITFALLS
Hydrocephalus has been categorized as obstructive
(noncommunicating) or nonobstructive (communicating).
Most cases of pediatric hydrocephalus, even congenital, have a
delayed diagnosis.
Hydrocephalus is rarely a stand-alone diagnosis and is often
secondary to additional pathology.
Hydrocephalus is the excess accumulation of cerebrospinal fluid (CSF),
usually as the result of obstruction in CSF absorption, resulting in raised
ICP. CSF is produced by the choroid plexus which is located within all four
ventricles in the brain. Under normal conditions, the CSF exits the fourth
ventricle to circulate in the subarachnoid space to be absorbed back into the
venous system largely through arachnoid villi located at the superior sagittal
sinus. Obstructive (or noncommunicating) hydrocephalus does not allow for
the CSF to leave the ventricular system, and nonobstructive (or
communicating) hydrocephalus occurs when the obstruction to CSF
absorption lies outside the ventricular system in the subarachnoid space or
at the arachnoid villi.
Common causes of obstructive hydrocephalus include stenosis of the
cerebral aqueduct (from congenital causes, midbrain tumors, following
hemorrhage or infection) and posterior fossa tumors. Common causes of
nonobstructive hydrocephalus include scarring of the subarachnoid space
and arachnoid villi following intraventricular hemorrhage (IVH) in
premature infants or meningitis. In congenital conditions such
myelomeningocele, the cause of hydrocephalus is likely multifactorial and
may involve both obstructive and nonobstructive elements. Genetic causes
are a less likely cause, including X-linked aqueductal stenosis and primary
ciliopathies.

Current Evidence. Infections are a common cause of hydrocephalus in
infants and children. An estimated 1% of pediatric patients who survive
bacterial meningitis, including gram-negative organisms (particularly
Escherichia coli ) which occur most frequently in the neonatal age group,
Haemophilus influenzae, Streptococcus pneumoniae, and group B
streptococci, develop progressive hydrocephalus. Other less common
infectious causes of hydrocephalus in children include tuberculosis
meningitis whose worldwide prevalence is rising, toxoplasmosis (or other
members of the TORCH group) usually diagnosed in the perinatal period,
and viral meningitis and encephalitis. Head trauma has been recognized as a
common cause of hydrocephalus. About 4% of patients develop
posttraumatic hydrocephalus requiring surgical CSF diversion. True
congenital hydrocephalus, meaning hydrocephalus present at birth, has an
estimated incidence of 0.2 to 0.8/1,000 live births in the United States. The
incidence of congenital hydrocephalus associated with conditions, such as
Dandy–Walker
malformation
(approximately
85%
to
95%),
myelomeningocele (approximately 80% to 90%), and IVH of prematurity
(approximately 35%), is better established.
Midline arachnoid cysts and tumors related to the ventricular system can
cause hydrocephalus by obstruction of the CSF pathways. Tumors may also
cause hydrocephalus by spilling blood or protein into the CSF, making the
CSF more viscous, overloading the absorptive capacity of the arachnoid
villi, and resulting in a communicating hydrocephalus.

Clinical Considerations
Clinical Recognition. Infants presenting symptoms include macrocephaly,
bulging fontanelle, excessive irritability, lethargy, or vomiting. Sunsetting
of the eyes may be present. This usually occurs later in the clinical course
and consists of a spectrum of findings, including components of Parinaud
syndrome (downward eye deviation, lid retraction, and convergenceretraction nystagmus). As raised ICP progresses, infants may develop
bradycardia and/or apneic episodes.
In older children, the more common presenting symptoms include
headache, nausea, or vomiting. These symptoms tend to be more common
in the mornings, when ICP is higher after having been recumbent overnight.
Other symptoms may include visual field deficits or double vision. This


could be the result of severe papilledema or the because of the underlying
cause of hydrocephalus, for example, a large suprasellar tumor causing
obstructive hydrocephalus and compressing the optic chiasm. Double vision
might be described, usually from a unilateral or bilateral abducens nerve
palsy, a classic false-localizing sign in raised ICP. Focal neurologic deficits
attributable to the underlying cause of the hydrocephalus, such as ataxia
from a posterior fossa tumor or bitemporal hemianopia from a suprasellar
tumor, may also be present.
Clinical Pitfall. Benign macrocephaly is the most common diagnosis for
an increasing head circumference. The typical infant, more commonly
male, will be one whose head circumference has risen to or above the 98th
percentile; but without a bulging fontanelle nor overt clinical signs of
increased ICP. Brain imaging (by ultrasound, CT, or MRI) will show
enlarged subarachnoid spaces over both frontal lobes. This has sometimes
been termed “extraventricular obstructive hydrocephalus,” although it is not
truly hydrocephalus.

Diagnostic Imaging. Hydrocephalus is ultimately diagnosed with cranial
imaging. A CT scan provides very good detail to make the diagnosis, is
readily available, and can be done very quickly. It does, however, expose
the child to radiation. Axial CT imaging will show enlarged ventricles. The
pattern of enlarged ventricles, both lateral ventricles and third ventricle (or
“triventricular”) or all four ventricles, will vary depending on the etiology
of the hydrocephalus ( Fig. 122.4 ). MRI provides greater anatomical detail
of the brain and ventricles, but it can be less readily available and may
require use of a general anesthetic. Depending on the results of a CT, an
MRI may be necessary, particularly if a tumor is suspected or if CT is
unable to clearly elucidate the etiology. A fast-spin, limited sequence MRI
may also be considered to evaluate ventricular anatomy with radiation
exposure or need for sedation. Ultrasound may be the most appropriate
imaging modality for infants with suspected benign macrocephaly and a
patent anterior fontanelle. This may confirm diagnosis and no further
imaging may be necessary.
Management. When assessing a child with hydrocephalus, the acuity of
the situation needs to be thoroughly assessed. If the child is in extremis, for
example, an obtunded child or a lethargic infant with bradycardia, the
situation is emergent. After ensuring the basics of airway and


cardiorespiratory maintenance, emergent cranial imaging and assessment by
a neurosurgeon are essential. Definitive treatment will require some form of
surgery. In some cases, there may be discreet tumor mass causing
obstructive hydrocephalus and the goal of surgery will be tumor resection,
which may relieve the hydrocephalus. In other situations, treatment will
require diversion of the CSF itself, in the form of either a CSF shunt or an
endoscopic third ventriculostomy (ETV).

FIGURE 122.4 An approximately 4.7 × 3.3 × 3.5 cm T1 hypointense, minimally
heterogeneous, circumscribed mass fills the fourth ventricle, which is effaced toward
the right, and displaces the pons and medulla anteriorly. There is resultant mild–
moderate dilatation of the lateral ventricles, third ventricle, and cerebral aqueduct.