Hydrocephalus in Children

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CHAPTER 186 Hydrocephalus in Children

Approach to the Patient

John R.W. Kestle

For years, the management of hydrocephalus has been the most common problem facing neurosurgeons who treat children. In most pediatric neurosurgery practices, hydrocephalus is responsible for 40% to 50% of the surgical interventions and clinic visits.

Recently, however, some evidence suggests that the incidence of pediatric hydrocephalus is decreasing. The number of first shunt insertions for children younger than 17 years decreased substantially in Canada between 1991 and 2000.¹ The decrease may be partially related to a decline in the number of children with spina bifida. Case control studies of the effects of folic acid have shown a significant reduction in the incidence of neural tube defects, which have a high association with hydrocephalus.² Furthermore, after a significant increase in the incidence of intraventricular hemorrhage between the 1970s and 1980s, there has been a marked decrease as experience with managing very preterm infants has grown. This too likely contributes to a decreased incidence of hydrocephalus in children.³ Societal decisions about how to treat very premature infants or those with significant malformations diagnosed in utero⁴ may also influence the incidence of hydrocephalus in live births.

Despite these trends, the burden of this illness remains large. Using the Healthcare Cost Utilization Project Kids’ Inpatient Database, a cross-sectional survey was performed in 1997, 2000, and 2003. Each year there were almost 40,000 admissions, approximately 400,000 hospital days, and between $1.4 billion and $2 billion in hospital charges for pediatric hydrocephalus. This accounted for 3.1% of all pediatric hospital charges. In addition, the children identified in this cross-sectional study had an increasing frequency of comorbidities.⁵ Clearly, pediatric hydrocephalus represents a huge burden of illness for children and is part of the daily lives of neurosurgeons in general and those treating children in particular. As a further testament to the frequency of hydrocephalus, the Hydrocephalus Clinical Research Network, a newly formed cooperative clinical trial group consisting of four pediatric neurosurgical centers, accumulated almost 1000 shunt procedures in the first 8 months of data acquisition.

Presentation

The clinical manifestations of pediatric hydrocephalus are those of raised intracranial pressure, which vary with age. An infant with open sutures usually presents with a gradually increasing head circumference. The importance of head measurement cannot be overemphasized. Standard head circumference charts should be part of the medical record of every child, especially those in whom hydrocephalus is considered a possibility. Specific charts are available for premature infants as well as for children with achondroplasia. The most important finding is a head size crossing percentiles. Some children have larger heads than others, and an isolated finding of a large head in a well baby is usually not too concerning; however, serial measurements that indicate a head circumference crossing percentile curves should be investigated. Unusual irritability or excessive vomiting with no other explanation may be attributed to hydrocephalus, as may eye movement abnormalities, especially downward deviation of the eyes (“sunsetting”), or sixth nerve paresis.

As a child gets older and the sutures fuse, the presentation differs. The head size can still cross percentiles, but it does so very slowly, so changes in percentile growth become less helpful as a sign of hydrocephalus. In these children, the presentation usually includes headache and eventually nausea and vomiting. The dementia, ataxia, and incontinence seen in adult normal-pressure hydrocephalus are not part of the pediatric presentation. Papilledema may occur in long-standing cases if the onset is after suture closure. A child whose hydrocephalus begins while the sutures are open but presents later usually does not have papilledema but does have a very large head. Presentation beyond the first few years of life usually indicates hydrocephalus secondary to an acquired disorder, such as tumor, head injury, or meningitis.

The decision to treat a child with ventriculomegaly can be very difficult. Once a shunt has been implanted, it is very difficult to determine whether it can be removed. The use of adjunctive measures, such as intracranial pressure monitoring,⁶ magnetic resonance spectroscopy,⁷ and the magnetic resonance measurement of cerebral blood flow,⁸ has been reported in difficult cases, but the decision to treat is usually based on observation over time. Progressively increasing head size, enlarging ventricles, or progressive symptoms are the most common measures and form the most solid basis for making the decision to treat.

Disease-Specific Considerations

Congenital Hydrocephalus

The majority of children with hydrocephalus present at or soon after birth. Many of them have aqueduct stenosis, Dandy-Walker malformation, holoprosencephaly, or other more generalized malformations of brain development. Aqueduct stenosis in males may be X-linked.⁹ In these children, the hydrocephalus is usually quite severe, and they have the clinical finding of adducted thumbs (Fig. 186-1). There may be other affected males in the family or a maternal history of spontaneous abortion.

FIGURE 186-1 Adducted thumb in a newborn with X-linked aqueduct stenosis.

(From Gluf W, Kestle J. “Cortical thumb sign” in X-linked hydrocephalus. Pediatr Neurosurg. 2002;37:107-108.)

Dandy-Walker malformation is a less common but important cause of infantile hydrocephalus. It is an abnormality of cerebellar development resulting in an extremely large fourth ventricle, elevation of the tentorium, and, in some cases, supratentorial hydrocephalus. The large fourth ventricle usually does not require treatment, but progressive enlargement of the supratentorial ventricles should be evaluated in the same manner as other forms of hydrocephalus.

Hydrocephalus Associated with Myelomeningocele

A newborn with myelomeningocele undergoes closure of the spinal defect and then observation for the development of hydrocephalus. In the past, 80% of children were thought to require ventriculoperitoneal shunt placement, but reduced rates of shunt placement have recently been reported.¹⁰ The most common manifestations of hydrocephalus in these children are increasing head circumference, splitting sutures, and full fontanelle, but some children may develop a large pseudomeningocele at the myelomeningocele repair site or a cerebrospinal fluid leak. These manifestations are often thought to be related to hydrocephalus and require the placement of a shunt. The importance of hydrocephalus in this population is emphasized by a multicenter trial funded by the National Institutes of Health that aims to randomize 200 fetuses to in utero or postnatal myelomeningocele closure. Based on suggestive preliminary data,¹¹ the trial is testing the hypothesis that in utero closure can reduce the need for shunt placement by reducing the incidence of Chiari II malformation, the major cause of progressive hydrocephalus in this patient population.

Arachnoid Cyst

Midline and posterior fossa arachnoid cysts in newborns commonly cause obstructive hydrocephalus. These may occur in the suprasellar area (Fig. 186-2), quadrigeminal cistern (Fig. 186-3), or cerebellopontine angle. Endoscopic fenestration of the cyst rather than treating the ventricular system may relieve obstruction and reestablish normal flow.

FIGURE 186-2 Magnetic resonance images of a 16-month-old girl with a progressively enlarging head from obstructive hydrocephalus secondary to suprasellar arachnoid cyst before (A) and 6 months after (B) endoscopic cyst fenestration into the third ventricle and prepontine cistern.

FIGURE 186-3 Magnetic resonance images of a quadrigeminal cistern arachnoid cyst with obstructive hydrocephalus in an 18-month-old girl with progressive head enlargement before (A) and 5 years after (B) endoscopic fenestration into the lateral ventricle.

Posthemorrhagic Hydrocephalus

Intraventricular hemorrhage in premature newborns is common and is related to the degree of prematurity and the birth weight.¹² The probability of developing posthemorrhagic hydrocephalus depends on the grade of intraventricular hemorrhage. An overall 40% incidence of ventriculomegaly has been reported,¹³ but the incidence can be as high as 70% in patients with grade IV intraventricular hemorrhage.¹⁴ In managing these children, it should be recognized that a significant rate of arrest or resolution of this type of hydrocephalus has been reported.¹⁵ In these tiny infants, ventriculoperitoneal shunt insertion can be difficult and has a high rate of complications. A number of options for delaying shunt insertion have been used, including serial lumbar punctures or treatment with furosemide (Lasix) and acetazolamide (Diamox). None of these measures has been shown to reduce the incidence of long-term hydrocephalus in randomized trials.¹⁶^,¹⁷ Temporizing with either a subgaleal shunt or a ventricular reservoir until the child reaches a weight of 1500 to 2000 g is a common practice. The proportion of children who receive such a temporizing measure and go on to permanent ventriculoperitoneal shunting is approximately 70% to 90%.¹⁸ An aggressive approach to reduce hydrocephalus after premature intraventricular hemorrhage was recently attempted using drainage, irrigation, and fibrinolytic therapy. Although a promising pilot study showed a reduced requirement for shunt surgery,¹⁹ a prospective randomized trial was stopped early because of an increased rebleed rate in the treatment group.²⁰ Despite that, the 2-year follow-up showed a reduction in death or severe disability.²¹

Hydrocephalus Associated with Brain Tumors

The tendency for children’s brain tumors to occur in the posterior fossa and midline leads to a high incidence of associated hydrocephalus. Management with preoperative shunt placement is no longer common practice, and most surgeons opt to remove the tumor and monitor for the development of hydrocephalus. Recently, third ventriculostomy performed before tumor removal was reported to reduce the risk of hydrocephalus significantly.²² The criticism of this approach is that some of these third ventriculostomies may be unnecessary because a proportion of children will not develop progressive hydrocephalus after tumor removal. A validated patient score for predicting the development of hydrocephalus in these children before tumor resection has been reported (Table 186-1).²³ Based on age, papilledema, severity of hydrocephalus, metastatic disease, and estimated preoperative tumor type, the chance of developing hydrocephalus can now be predicted before resection of the tumor (Table 186-2). Evaluating these factors allows a more informed discussion with patients and families and possibly the selective use of endoscopic third ventriculostomy before tumor surgery. External ventricular drain insertion at the time of tumor removal is common for tumors within the fourth ventricle but may be avoided in cerebellar hemispheric tumors. Following surgery for tumors in the lateral ventricle that are associated with hydrocephalus, the surgical tract may lead to postoperative decompression of the hydrocephalus into the subdural space. When this collection persists as a subdural hygroma, it may require treatment with a subdural shunt.

TABLE 186-1

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