AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

Hydrocephalus is defined as excess cerebrospinal fluid (CSF) accumulation in the head caused by disturbance of formation, flow, or absorption. The term stems from the Greek hydro (water) and cephali (head).

Infantile hydrocephalus is associated with the following:

• Congenital anomalies
• • Aqueductal stenosis
  • Spina bifida
  • Arnold-Chiari II malformation
• Less common conditions
• • Dandy-Walker syndrome
  • Encephaloceles
  • Viral or parasitic infections
  • Arachnoid cysts
  • Intracranial neoplasms
  • Vascular problems
  • Nutritional deficiencies
  • Poisonings
• Acquired conditions
• • Perinatal intraventricular hemorrhage (IVH)
  • Meningitis
• Trauma - Closed head injury

History of the Procedure

In the 1940s, before shunting was established, children with hydrocephalus had a poor prognosis. Most patients were not offered treatment, and only 20% of children who did not undergo surgery for hydrocephalus reached adulthood. Furthermore, children who survived had a 50% chance of having permanent brain damage. Outcomes improved after the introduction of valved shunt systems by Nulsen and Spitz in 1952 and after the development of silicone systems by Holter and Pudenz in the 1960s. Most children with hydrocephalus currently reach adulthood if the shunt is appropriately maintained. In a 20-year follow-up survey of children who received shunting in the 1970s, more than half of them graduated from mainstream education.

The outcome of patients with spina bifida has also improved. In a review of a cohort of patients treated in the 1970s for spina bifida aperta, 52% of the patients were alive 20 years after treatment. Most of the deaths occurred in the first year of life, mostly due to renal and respiratory problems associated with spina bifida. Only a few of the deaths were related to hydrocephalus. In a similar, but more recent, review of children treated in the 1980s, only 27% died; most of them died in the first year of life from causes related to spina bifida rather than hydrocephalus. In a recent survey of adults with spina bifida, 6% of patients died from shunt-related problems or died after craniovertebral decompression for Arnold-Chiari II malformation.

Problem

Hydrocephalus is caused by either increased production of CSF or impaired circulation and absorption. Hydrocephalus caused by impaired circulation is called obstructive hydrocephalus because CSF circulation is anatomically blocked. Hydrocephalus caused by increased production or impaired absorption of CSF is called communicating hydrocephalus because CSF circulation is not anatomically blocked. According to some authorities, all cases of hydrocephalus are obstructive (ie, patients with communicating hydrocephalus have a functional obstruction at the final stage of absorption at the arachnoid granulations).

Frequency

The incidence of infantile hydrocephalus is estimated at 3-5 cases per 1000 live births. The peak ages of presentation in this group include the first few weeks of life, age 4-8 years, and early adulthood. The latter 2 peaks represent delayed presentations of infantile hydrocephalus. An estimated 750,000 people have hydrocephalus, and 160,000 ventriculoperitoneal shunts are implanted each year worldwide. About 56,600 children and adolescents younger than 18 years have a shunt in place.

The incidence of myelomeningocele ranges from 0.2-2 per 1000 live births. The overall incidence of myelomeningocele has significantly declined in the last 2 decades because of improved maternal nutrition during pregnancy, including the addition of folic acid, a wider availability of prenatal diagnosis, and therapeutic termination of pregnancy. In a significant proportion of patients with open spina bifida, hydrocephalus is absent at birth but develops in the first few weeks or months of life. Hydrocephalus occurs in 15-25% of children with open myelomeningocele at birth; however, in most surgical series, the proportion of patients with myelomeningocele who require shunting reaches 80-90%. In a recent retrospective chart review, shunt placement has been shown to vary based on the level of the lesion, with a greater number of patients with thoracic lesions requiring shunts than those with lumbar or sacral lesions. Lesions at levels of T12 and above have also been associated with increased incidence of brain abnormalities and lower scores on psychometric testing than lesions at L-1 or below.

Etiology

The simplistic distinction of obstructive and communicating hydrocephalus is historically related to different conditions that cause or are associated with impairment of CSF circulation. Examples of conditions associated with obstructive hydrocephalus include congenital aqueductal stenosis, tumors of the ventricular system (eg, colloid cyst of the third ventricle, astrocytoma of the third ventricle), and tumors of the posterior cranial fossa (eg, cerebellar astrocytoma, medulloblastoma). An example of communicating hydrocephalus caused by CSF overproduction is the presence of choroid plexus papilloma in one of the ventricles. Examples of conditions with communicating hydrocephalus caused by impaired CSF absorption include IVH, meningitis, and head injury. Occasionally, obstructive and communicating hydrocephalus coexist and therefore cannot be differentiated.

Pathophysiology

Production of CSF is an active process that occurs at a rate of 0.35 mL/min. Absorption of CSF at the arachnoid granulations is also an active process and requires at least 6.8 mm of water pressure to overcome the venous blood pressure inside the sagittal sinus. During a 24-hour period, a total of 500 mL and 250 mL of CSF is produced and absorbed in adults and in children, respectively. At any given time, a total of 140 mL and 70 mL of CSF is present in the head in adults and in children, respectively. Normal CSF pressure inside the ventricles is 110 mm of water pressure. When CSF circulation is impaired, the resulting CSF accumulation leads to ventricular enlargement and a rise in intraventricular (and, hence, intracranial) pressure. In infants with open fontanelles, some of this rise in pressure is counteracted with enlargement of the head. When the maximum capacity for head enlargement has been exceeded, rapid deterioration follows because of raised intracranial pressure.

In children with aqueductal stenosis, the aqueduct of Sylvius is narrower than usual or is completely occluded and the CSF flow is obstructed. Some believe that aqueductal stenosis is the primary deformity and leads to ventriculomegaly. Others believe that ventriculomegaly is the primary deformity (because of altered abnormal ventricular wall compliance) and leads to secondary aqueductal stenosis caused by continuing compression of the midbrain.

In children with postmeningitic or posthemorrhagic hydrocephalus, protein (meningitis) or blood degradation products (IVH) are hypothesized to occlude arachnoid granulations, rendering CSF absorption relatively ineffective.

Several factors are implicated in the pathogenesis of hydrocephalus in children with myelomeningocele; these include the Arnold-Chiari II malformation, a degree of aqueductal stenosis, anomalous venous drainage in the posterior fossa caused by compression of the sigmoid sinuses, open myelomeningocele, and the presence of other CNS malformations.

Extensive deformity of the posterior fossa and its structures is associated with Arnold-Chiari II malformations. The brain stem has abnormal disposition with respect to the midbrain and the tentorial hiatus, the posterior fossa has smaller capacity than usual, the fourth ventricle is displaced caudally, and the cerebellar tonsils through the foramen magnum are significantly prolapsed. These anatomic factors all contribute to the impairment of CSF circulation.

Although the development of hindbrain herniation during gestation in myelomeningocele was once thought to be the result of cord tethering “pulling” on the brain tissue, hindbrain herniation is now believed to be caused by the progressive caudal migration of the hindbrain in association with the low-pressure conditions created in the spine by the open myelomeningocele. Continued loss of CSF soon after birth exacerbates the hindbrain hernia and the associated hydrocephalus. This can lead to acute neurologic deterioration caused by a combination of raised intracranial pressure related to the ventriculomegaly and acute bulbar dysfunction caused by compression of the brain stem in the foramen magnum region. The neurologic state usually improves after ventricular shunting. In most patients, ventriculomegaly gradually develops within the first few weeks or months of life.

Hydrocephalus development can be temporally related to the closure of the myelomeningocele. In a small group of patients with open myelomeningocele, dramatic deterioration occurs after closure of the defect. The impaction of the hindbrain hernia plays a significant role in this acute deterioration.

In addition to the presumed effect of the low-pressure leak during gestation on development of Arnold-Chiari II malformation described above, the abnormal and exposed spinal tissue is theorized to sustain damage in utero through trauma and exposure to neurotoxic substances in amniotic fluid. This is thought to lead to neurologic deficits that are worse than if the exposure did not occur. Most recently, several surgical centers have attempted to lessen the effect of Arnold-Chiari II malformation, neurologic impairment, and need for shunting through the use of in utero surgical repair of the myelomeningocele. The first such repair was performed in 1997, after several animal models demonstrated benefit of the procedure. Studies of the outcomes of these surgeries have been somewhat promising, although still inconclusive.

A reduction in shunt-dependent hydrocephalus has been shown in children who underwent surgical correction at less than 25 weeks’ gestation, who had ventricular measurements of less than 17 mm at time of surgery, and who had an anatomic level lower than L3. An approximately 50% reduction in the need for shunts was reported in this select group. However, long-term follow-up was lacking. One study demonstrated a decrease in hindbrain herniation with improvement on serial fetal scans. However, another study failed to demonstrate any difference in progression of ventriculomegaly in patients who underwent intrauterine repair when compared with controls.

Several small studies have investigated leg and neurologic function and have not provided clear evidence that in utero repair improves either function. A study involving 30 children (43% of whom required a shunt) investigated neurodevelopmental outcome at 2 years following treatment. The study revealed that 87% of the children had normal or mildly delayed cognitive language and personal-social skills.

In utero repair is certainly not without risk to both the mother and the fetus. In fetuses, a 4% risk of mortality and an 11% risk of morbidity (primarily from prematurity) is associated with the surgery. In mothers, uterine dehiscence, uterine rupture, and hysterectomy are also risks. Development of minimally invasive techniques may improve these outcomes, but they have not yet been successful in this procedure. Because the risks and benefits are not clear, a randomized control trial (the Management of Myelomeningocele Study [MOMS]) funded by the National Institute of Child Health and Human Development is currently underway  at 3 US centers in an attempt to definitively evaluate the risks and benefits of in utero repair of myelomeningocele.

Clinical

Infants with hydrocephalus develop an enlarging head with bulging fontanelle, enlarged scalp veins, macrocrania, suture diastasis, and positive Macewen (ie, cracked pot) sign. If the hydrocephalus is not treated, these infants develop sunset eyes, recurrent vomiting, and, later, respiratory arrest. Persistent CSF leak from the repaired spinal wound almost invariably indicates active hydrocephalus, even if the ventricular size is only modestly enlarged and the anterior fontanelle is not bulging.

The particular concern in children with myelomeningocele is the presence of hindbrain hernia in the context of the Arnold-Chiari II malformation, which can cause early clinical symptoms of bulbar palsy due to compression of the brainstem and can remain unnoticed by inexperienced observers or be confused with symptoms of shunt malfunction or untreated hydrocephalus. Poor feeding, recurrent vomiting, poor sucking, generally subdued behavior with poor crying, high-pitched cry or stridor caused by vocal cord paralysis (a predictor of poor outcome), episodes of apnea, extremity weakness in older children, and recurrent aspiration (often manifesting as recurrent pneumonia) can all be manifestations of brain stem dysfunction caused by hindbrain hernia and aggravated by ventricular dilatation. Approximately 20% of children with myelomeningocele who also have an Arnold-Chiari II malformation develop brainstem symptoms. Myelomeningocele is also a contributor to mortality and morbidity in the first 2 decades of life.

Older children with closed fontanelles develop clinical signs of intracranial hypertension without progressive head enlargement. They develop headaches, blurred vision, decline in intellectual performance, and gradual drowsiness, which, if left untreated, lead to coma and death due to respiratory arrest.

INDICATIONS

Section 3 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

Children with a clinical picture of active hydrocephalus and significant ventriculomegaly (often with evidence of periventricular lucency indicating raised CSF pressure in the ventricular system) require treatment early in life. However, children with mild or moderate ventriculomegaly and a head circumference within the reference range may not require initial treatment. Watchful waiting may be adopted during the first few months of life, and head circumference monitoring and repeated ultrasonography, CT scanning, or MRI are helpful in deciding whether shunting is required.

Age, prematurity status, and weight are significant considerations for the timing of treatment in children. In general, shunting is avoided, if possible, in children younger than 6 months because they have an increased risk of infection. For the same reason, shunting should be deferred, if possible, in premature babies who weigh less than 1.5 kg until they have gained weight. These considerations often arise in children with posthemorrhagic hydrocephalus because they are often premature and small for age.

If feasible, shunts should be placed when the myelomeningocele is closed because it appears to protect patients from CSF leak from the spinal wound, which can lead to shunt infection, and improves the chances for better development by reducing intracranial hypertension early. One of the signs of ongoing hydrocephalus after closure of myelomeningocele is persistent CSF leak. Children with open myelomeningocele in whom closure of the defect has been delayed may already have CSF infection. In such circumstances, CSF microbiological testing should be performed; if CSF infection is present, external ventricular drainage should be performed for 7-10 days in conjunction with antibiotic treatment, until CSF infection is controlled and a shunt can be inserted.

Although children with IVH may have active hydrocephalus early in life, shunting is often difficult to consider because the CSF is heavily blood stained, the protein content is too high (>1 g/dL), or both. In such cases, the traditional approach is to insert an external ventricular drain until the CSF clears and a shunt can be inserted. Injection of tissue plasminogen activator (TPA) into the ventricles has been attempted in an effort to accelerate blood clearance from the CSF, with moderate success. This therapeutic maneuver has not yet gained universal acceptance.

An issue that merits attention is the need to decide whether shunting is indicated in older children or young adults who have myelomeningocele and untreated ventriculomegaly. Some patients  have the typically shaped ventricles of hydrocephalus that are caused by spina bifida but do not appear to have tension, with no periventricular flow of CSF as seen on T2-weighted MRI and no symptoms (eg, headache, drowsiness, diplopia, bulbar features) that suggest active hydrocephalus. If these patients never receive shunting, they should be serially monitored with intelligence and psychometric testing.

If a patient has no clinical symptoms and his or her psychometric test results indicate stability, shunting based solely on radiologic appearance should be discouraged because the risks outweigh the benefits, and serial follow-up should be continued. Similarly, any intervention on the shunt should be considered cautiously in patients who already have received shunting. Because shunts may be disconnected or may appear to have long since stopped working, regarding the situation as compensated hydrocephalus and choosing to remove the shunt, especially if it is causing local discomfort in the neck, is tempting. However, shunts that have been implanted for years acquire a tube of strong fibrous tissue that surrounds them along their entire length. Even though the tube may appear fractured on radiographs, CSF is bridging the gap guided by the encircling fibrous tube. Such shunts are actually functioning, and any attempt to remove them without instituting any alternative means of CSF drainage (eg, third ventriculostomy) may cause neurologic deterioration. However, if the patient has subtle symptoms or a declining intelligence based on psychometric testing, treatment should be offered. In such cases, patients who have not received shunting should receive them; in those with shunts, the shunt systems should be evaluated and explored and revised if necessary.

RELEVANT ANATOMY

Section 4 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

CSF is typically produced by the choroid plexus of the ventricles and circulates in one direction from the lateral ventricles to the third ventricle and through the aqueduct of Sylvius to the fourth ventricle. From the fourth ventricle, CSF exits the brain through 3 separate openings: one in the midline (foramen Magendie) and one on either side (foramina Luschka). It enters the subarachnoid space at the foramen magnum, circulates down to the spine, and then circulates up again to the surface of the brain, where it is absorbed at the arachnoid granulations. These are sievelike structures where the CSF enters the venous circulation, leading to the sagittal sinus.

In children with hydrocephalus, ventricular dilatation affects the part of the ventricular system that is before the level of the obstruction, with respect to CSF circulation. Thus, in aqueductal stenosis, the lateral and third ventricles are dilated, but the fourth ventricles are not. In contrast, in postmeningitic or posthemorrhagic hydrocephalus, all ventricles are dilated because the obstruction is at the level of the arachnoid granulations and at the end of the intracranial CSF circulation conduit.

CONTRAINDICATIONS

Section 5 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

Relative contraindications to treatment of infantile hydrocephalus include severe CNS malformations that are regarded as incompatible with normal development, such as some of the congential neurodevelopmental syndromes associated with severe malformation of a large part of cerebral substance (ie, anencephaly); in these cases, neonatologists prefer to counsel parents against treatment of hydrocephalus. The same considerations are applied to severe cases of IVH in which radiologic investigations clearly indicate that the hemorrhage has damaged significant large parts of the brain.

WORKUP

Section 6 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

Imaging Studies

• Ultrasonography
  
  
  • Currently, most fetuses undergo in utero ultrasonographic scanning.
  • Ultrasonography allows for good identification of any ventricular dilatation that indicates active hydrocephalus. In such cases, or in patients who present with progressive head enlargement to pediatricians or family doctors, ultrasonography is usually performed first because it is widely available and does not expose the child to ionizing radiation.
  • In babies with open fontanelles and large heads, ultrasonography reveals the enlarged ventricular system and any mass lesions or hemorrhage. However, the anatomic detail produced by ultrasonography remains poor and serves only as a guide to further investigations.
• CT scanning 
  
  
  • Once hydrocephalus is suspected, either clinically or based on ultrasonography findings, the diagnosis must be confirmed with a more detailed investigation.
  • In most parts of the world, CT scanning remains the most widely available neuroimaging investigation. Because image acquisition is rapid, the study does not require sedation of the child and, in most cases, is helpful for obtaining an accurate diagnosis.
  • CT scanning provides a good image of the dilated ventricular system and any obstructive lesions, such as brain tumors, or associated abnormalities, such as arachnoid cysts. Anatomic detail is generally good, and, in the vast majority of cases, proceeding to treatment based on CT scan findings is regarded as safe. However, if endoscopic treatment is considered, MRI should be performed.
• MRI 
  
  
  • For the last 2 decades, MRI has played an increasing role in the management of hydrocephalus in children. Unfortunately, it still is not as widely available as CT scanning.
  • The need for sedation (or even general anesthesia) to obtain good images is a major consideration, especially in very young infants, because acquisition takes several minutes or more and any movement severely deteriorates picture quality. This is particularly problematic in children with associated congenital conditions that cause poor respiratory drive.
  • MRI shows structures of the brain with superior anatomic detail and assists the surgeon in choosing the best treatment. MRI is especially necessary in conjunction with endoscopic treatment, in which the surgeon must verify the presence of aqueductal stenosis (see Images 2-4) or any intracranial cysts that may be fenestrated, and in determining the relationship of important anatomic structures (eg, the floor of the third ventricle to the basilar artery) in children with aqueductal stenosis.
  • The use of phase-contrast cardiac-gated sequences can provide information on CSF flow through the aqueduct, and ventriculostomy can provide information on patency of the stoma.
  • Children born with open myelomeningocele have a very high incidence (close to 100%) of hindbrain hernia (see Image 6). Marked hydrocephalus is present in as many as 15-20% of these patients, and a further 20% have moderate ventriculomegaly at birth. A large proportion of patients (as many as 90%) eventually develop clinical hydrocephalus. The lateral ventricles have a characteristic appearance in almost all patients with spina bifida (see Image 5); the occipital horns are more dilated than the frontal horns and the long axis of the lateral ventricles tend to be parallel. A contributing factor may be the partial or complete absence of the falx and absence of the septum pellucidum in a very large proportion of these patients. MRI produces a good image of the hindbrain hernia, the small posterior fossa, and the midbrain deformity with kinking of the aqueduct.

TREATMENT

Section 7 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

Medical therapy

In general, medical therapy of hydrocephalus is far inferior to surgical management of the condition. Medical therapy has been used with limited success in an attempt to avoid shunting in patients with posthemorrhagic hydrocephalus. Prenatal administration of antenatal steroids may modestly reduce the incidence of IVH in premature infants. Postnatal use of indomethacin has been shown to reduce severe IVH in some studies, although improvement in cognitive functioning has not been documented. Diuretic therapy, such as the use of acetazolamide and furosemide, was invalidated as a therapy in one recent study of 177 infants.  In this study, the medications did not affect rates of shunt placement and may have impaired neurologic outcome. Fibrinolytic therapy is currently under investigation.

Serial lumbar puncture has been frequently performed after IVH to prevent or manage developing hydrocephalus, but no clear guidelines indicate when to initiate treatment and no explicit evidence of effectiveness has been reported. Early use of lumbar puncture (prior to evidence of head expansion) has been shown by meta-analysis to have no benefit.

Surgical therapy

In most cases, surgical treatment of hydrocephalus consists of ventricular shunt insertion. The shunt is an artificial device, made mostly of plastic (although some parts may be metal), that includes a catheter inserted in the ventricle of the brain (a one-way valve that allows the unidirectional flow of CSF out of the brain) and a distal catheter that drains the CSF to an extracranial location in the body. The most preferred distal site remains the peritoneum. However, other sites are available (eg, right atrium, pleura, gall bladder, ureter, bladder, sagittal sinus) in patients with other coexisting abdominal problems. In current practice, the overwhelming majority of shunts are ventriculoperitoneal.

All shunts are designed to maintain normal intracranial pressure. More than a dozen different commercial shunts are currently available. The design of the valve is controversial. Essentially, 2 types of shunts are available: the pressure-regulating shunt and the flow-regulating shunt (as well as 2 brands of programmable shunt valves). The pressure-regulating shunts are designed to maintain a difference of pressure between their inlet and outlet and allow flow of CSF once the preset pressure has been reached. The flow-regulating shunts are designed to allow a constant flow of CSF, simulating the normal flow. Despite different designs, large randomized trials have been unable to demonstrate differences between the various types. Different types of valves are seemingly associated with different types of complications. For example, the pressure-regulating valves are more prone to cause overdrainage complications, whereas the flow-regulating valves are more prone to cause valve obstruction.

Endoscopic third ventriculostomy (ETV) was first performed by Walter Dandy in the 1910s with moderate success and has recently experienced resurgence. The endoscopic equipment has improved, which has resulted in increased use of the procedure. ETV has a success rate of 70% when used in patients with aqueductal stenosis and is regarded by many as the procedure of choice in these patients. Endoscopic cyst fenestration can be used in the presence of arachnoid cysts in various locations (ie, suprasellar, interhemispheric, posterior fossa) with variable success.

Third ventriculostomy has been recently performed to treat hydrocephalus in children with myelomeningocele. However, the reported success rates are only approximately 30-40%. One possible explanation for the low success rate of third ventriculostomy is that most patients are infants or neonates when they receive initial treatment and do not have fully developed subarachnoid spaces. A frontal ventricular catheter attached to a blind reservoir or an Ommaya reservoir can be left in place and can be converted to a ventriculoperitoneal shunt if the third ventriculostomy fails. ETV can be used in children who have already received shunting and who present with shunt malfunction at an older age. The reported success rate is approximately 50%.  In such patients, an external ventricular drain should be used for the first few days following third ventriculostomy (especially if the shunt has been removed) to allow emergency decompression if the third ventriculostomy does not function adequately and the patient's condition rapidly deteriorates.

ETV may be more effective if it is combined with choroid plexus cauterization. Improved outcomes were reported in a recent study of select patients younger than one year. However, cauterization is not routinely performed and remains a controversial option; further study is needed.

Premature infants with posthemorrhagic hydrocephalus may benefit from placement of a subgaleal ventricular reservoir (an Ommaya reservoir), subgaleal shunt (which drains into a subgaleal pocket created during surgery), serial lumbar punctures, or external ventricular drainage as a temporizing measure. Placement of a permanent shunt may be avoided in as many as 25% of these children.

Preoperative details

Anesthetic factors must be considered, particularly those relative to respiratory function and reserve. Many of these patients are premature neonates who have poor respiratory reserve and may be experiencing physiologic jaundice when surgery is required. Because the magnitude of the surgery is not extensive, the circulating blood volume is usually not problematic, and a blood transfusion is likely to be unnecessary during shunt insertion or endoscopic ventriculostomy, unless a preexisting problem is present.

Intraoperative details

The importance of avoiding hypothermia and excessive blood loss in pediatric patients cannot be overemphasized; especially in neonates. Also, having a dedicated pediatric anesthesia team and operating room team are equally important. In addition, limiting operating room traffic during these procedures can be helpful in decreasing infections.

In most cases, shunt insertion involves making a posterior parietal or frontal burr hole through a small linear or curved skin incision. The peritoneal cavity is entered through a small linear incision either in the upper midline epigastric region or in the right upper quadrant. The distal tube is advanced from the cranial to the abdominal wound using a purpose-designed tubular dissector advanced in the subcutaneous fat. In typical cases, if a posterior parietal burr hole is used, the shunt valve is situated behind the ear, avoiding the need for a step incision, and is usually easily palpable by the patient and parents. Administering prophylactic antibiotics, usually cephalosporin or vancomycin, is common at the commencement of the operation to lessen the likelihood of shunt infection.

In children born with open spina bifida who undergo simultaneous shunting and myelomeningocele closure, additional precautions should be taken to maintain sterility of the surgical fields. Most neurosurgeons prefer to close the myelomeningocele with the child prone and subsequently turn the child on his or her back for the shunt placement while adequately protecting the newly repaired spinal wound with ample padding.

ETV is traditionally performed through a frontal burr hole situated just anteriorly to the coronal suture. A rigid or flexible endoscope is preferred. The third ventricle floor is perforated using a purpose-designed monopolar diathermy with retractable tip or another similar purpose-designed dissector. After formation, the stoma is commonly dilated using some kind of purpose-designed balloon dilator.

Perforation of the third ventricle floor is the most delicate and important phase because perforation of the adjacent basilar artery is a risk. ETV can be particularly difficult in children with myelomeningocele because the ventricular anatomy is often abnormal, the third ventricle floor is thicker and more difficult to penetrate, the size of the third ventricle is smaller in these children than in those with aqueductal stenosis, or the septum pellucidum is absent, which can lead to disorientation in the inexperienced operator. In general, inexperienced operators should avoid ETV in children with hydrocephalus caused by myelomeningocele. Apart from damage to the basilar artery, another potential source of intraoperative difficulty is damage to the choroid plexus, which can lead to hemorrhage that clouds the operative field. Most nonarterial bleeding stops with gentle warm irrigation.

Failure to perforate the Liliequist membrane may also result in ETV failure. Preoperative MRI is very important because it reveals the bowing of the third ventricle floor and its relationship to the basilar artery. Bowing of the third ventricle floor correlates with a pressure gradient between the ventricular system and the extraventricular CSF spaces. If the third ventricle floor is not bowed, the success rate of ETV is significantly decreased.

In cases of shunt revision or shunt removal after successful ventriculostomy, rupture of the choroid plexus during retrieval of the ventricular catheter is common and can lead to life-threatening hemorrhage. Different techniques can be used to avoid this complication; the most common of these techniques involves insertion of a stylet into the catheter lumen, allowing for coagulation with the diathermy before the catheter is retrieved. However, if the ventricular catheter is not easily removed, it should be left in place and an additional catheter should be placed. Image guidance can also be very helpful in ventricular catheter placement, especially in patients with loculated hydrocephalus and cannulating complex cysts.

Spina bifida is a midline defect in the mesenchymal-derived tissues and is classified as closed or open neural tube defects (NTDs). Closed NTDs do not involve exposed neural tissue and do not leak CSF. Open NTDs are subclassified into myelomeningocele (most common), myeloschisis, or hemimyelomeningocele (most rare). The goals of surgery are to preserve neural function, to prevent infection, and to prevent long-term complications such as an epidermal or dermal inclusion cyst and cord tethering.

Operative correction starts with anesthesia and positioning. Heat and blood loss are of vital importance in pediatric operative correction because both account for significant morbidity and mortality. The anesthetic can be modified if electrophysiologic monitoring and intraoperative nerve testing are desired.

The patient is usually placed prone on the operating room table, with sufficient padding of all pressure points. Open NTDs are cleansed with either sterile normal saline or lactated ringers; Betadine and other neurotoxic agents should be avoided. The wound is prepared and draped in a sterile fashion, and CSF is obtained for culture.

The neural placode is circumferentially incised, and every attempt is made to identify and separate all layers to allow for a multilayered closure that can be performed with fine running absorbable sutures. Inclusion of the epidermal tissue in the deep layers of the closure should be avoided because this can lead to late formation of a dermal inclusion cyst, an epidermal inclusion cyst, or both. The dura mater should be widely mobilized and closed without constricting the intradural contents, which can increase the likelihood of arachnoid adhesions and tethering.

Tissue should be conserved and trimmed only after it is definitively not needed for the closure. Working in conjunction with a plastic surgeon is helpful when myofascial flaps, rotational skin flaps, partial-thickness skin grafts, or flank-relaxing incisions are needed to close the defect. Closure in a transverse direction is preferable to a horizontal direction because the former offers better cosmesis and keeps the wound farther from the anus. In patients with severe hydrocephalus, placement of a ventriculoperitoneal shunt first theoretically decreases the risk of shunt contamination.

Postoperative details

After successful completion of shunt insertion or revision in patients in whom a differential-pressure valve has been implanted, elevation into the upright position is commonly avoided to prevent shunt overdrainage and subdural hematomata formation. In contrast, patients in whom a flow-regulating shunt has been implanted are commonly elevated to 30° or more the day after the implantation to promote CSF drainage. The efficacy of these practices is unclear. Feeding of very young babies can commence soon after surgery.

Patients who undergo shunt revision tend to recover quickly, and they are usually discharged home a few days after surgery.

Follow-up

Postoperative follow-up a few weeks after shunt placement is usually necessary to ensure that the wound is healing well and that the head circumference is decreasing accordingly. Performing a CT scan and shunt series before discharge is customary to verify the position of the ventricular tube and to serve as future reference in case of possible shunt malfunction.

The issue of repeat scanning in the months after shunt insertion or ventriculostomy remains controversial. Certainly, satisfactory shunt function should be verified with at least one scan during the first year. In patients who undergo third ventriculostomy, cine phase-contrast MRI is mandatory to verify patency of the ETV stoma. Customarily, some surgeons perform yearly scanning, but the use of such routines is not universally accepted.

Currently, shunt malfunctions cannot be detected before they manifest clinically. Attempts to visualize CSF flow using ultrasonography or other imaging techniques have not been met with universal acceptance because they are associated with some false-negative and false-positive results.

Spina bifida requires ongoing follow-up for life because problems unrelated to hydrocephalus appear at various stages and necessitate treatment. Patients with spina bifida have continuing urologic problems due to neuropathic bladder. Neurogenic bowel can cause debilitating social problems. Although neurogenic bowel and bladder are initially managed medically with medication, retrograde scheduled enemas, and routine clean intermittent catheterization, some patients and physicians opt for surgical treatment such as the Malone procedure for antegrade colonic enemas (MACE) and the Mitrofanoff procedure for ease of catheterization.

• In the Malone procedure, a section of bowel (typically the appendix) is made into a conduit from the colon to the abdominal wall. This is then used for daily antegrade enemas to maximize bowel continence.
• The Mitrofanoff procedure is similar in that a section of bowel (again, usually the appendix) is made into a conduit from the bladder to the abdominal wall for daily catheterizations.

These procedures are performed in the hope of increasing independence and quality of life in patients with spina bifida. Although the specific indications and quantitative benefits of these procedures have not been well documented, improvements in health and well being have been suggested.

Another option for bowel continence is the use of a cecostomy, wherein a synthetic tube is inserted into the cecum and becomes the conduit for antegrade enemas. This may be used in patients without an appendix or in patients who have undergone a Mitrofanoff procedure in which the appendix was used.

Retethering of the cord occurs in 15-20% patients with myelomeningocele and is characterized by progressive weakness of one or both legs, onset or progression of scoliosis, change in gait, change in bowel or bladder control or function, or lower back pain. This condition may be confused with shunt malfunction.

Orthopedic problems, such as scoliosis and foot deformities, also require careful follow-up because they are likely to necessitate surgical treatment. A consideration particular to children with myelomeningocele is the relationship between hydrocephalus and scoliosis, which is present in a very high proportion of these patients. Scoliosis deteriorates in the presence of untreated hydrocephalus and improves following successful shunting. Active hydrocephalus is postulated to exacerbate the compressive effect of the hindbrain hernia on the descending pathways at the craniovertebral junction, inducing neuromuscular imbalance.

Another consideration specific to hydrocephalus related to myelomeningocele is the high incidence of precocious puberty among female patients (as many as 16%). The mechanism may be hypothalamic dysfunction caused by congenital deformity of the midbrain. Precocious puberty does not appear to affect intellectual development. 

For excellent patient education resources, visit eMedicine's Brain and Nervous System Center. Also, see eMedicine's patient education article Spina Bifida.

COMPLICATIONS

Section 8 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

The patient and the doctor must have an ongoing commitment to manage the complications associated with shunting. Shunt complications can be divided into 3 categories: mechanical, infective, and overdrainage-related. As many as 80% of shunts develop mechanical complications at some stage, and one third to one half of these complications occur within the first year of shunt placement. An additional 15% of shunts fail in the second year, and 1-7% shunts per year fail after the second year. On average, each patient is likely to undergo 2-3 operations throughout childhood for shunt revision. The mortality rate associated with initial insertion is approximately 0.1%; mortality due to shunt failure ranges from 1-4%.

Infective complications occur in 5-10% of all shunt operations and are more common in younger patients, especially in those younger than 6 months. Most shunt infections manifest in the first 3 months after insertion, and almost all present within the first 6 months. Staphylococcus is the most common offending organism. The use of shunts impregnated with antistaphylococcal antibiotics may reduce the incidence of shunt infection.

Symptoms of shunt infection include redness and swelling along the surgical incision site, tenderness over the reservoir, swelling or drainage, nuchal rigidity, or abdominal pain. During the 1970s, when ventriculoatrial shunts were commonly used, an appreciable number of patients experienced bacterial endocarditis and shunt nephritis caused by direct bacteremia due to bacterial colonization of the shunt lumen. The change from ventriculoatrial to ventriculoperitoneal shunts substantially decreased complications of shunting.

Most shunt obstructions are related to obstruction of the ventricular catheter by glioependymal tissue, which grows into the lumen from the ventricular wall through the draining holes. In many shunt revision operations, as many as 30% of intraventricular hemorrhages occur during removal of the old catheter because of rupture of the choroid plexus, which has grown into the shunt lumen. Symptoms of acute shunt obstruction include headache, nausea and vomiting, papilledema, cranial nerve VI palsy, change in personality, and the setting sun sign (lack of upward gaze) in infants. Chronic failure may be heralded by accelerated head growth, loss of milestones, papilledema, optic atrophy, and change in seizure frequency.

A significant late complication is fracture or destruction of the shunt tube due to material degradation and fatigue (see Image 7). Common locations for distal tube fracture include the occipitocervical junction, the root of the neck, and the junction between the inferior border of the ribs and the abdominal wall. These are points of maximal mechanical stress where the material is degraded most.

Overdrainage of CSF is another significant shunt complication that is difficult to counteract. Early overdrainage leads to formation of subdural hematomas, which are difficult to treat, and ligation of the shunt is sometimes necessary. Late chronic overdrainage leads to the development of slit ventricles and mostly affects patients with differential pressure valves, which drain excess CSF when the patients assume the upright position, because of the siphoning effect of the column of fluid in the distal tube. Chronic overdrainage leads to collapse of the ventricles and intermittent shunt obstruction.

Siphoning is due to a pressure gradient between the proximal and distal ends and is a factor of the height multiplied by the mass of CSF multiplied by the acceleration of gravity. Siphoning usually becomes apparent when patients come out of recumbency. Antisiphon devices of different types have been developed to overcome overdrainage and are incorporated in many shunt systems, with variable success. Over the years, technical aspects of the shunt valves and the development of flow-regulating valves have improved the frequency of adverse effects related to overdrainage and mechanical complications.

Endoscopic treatment of hydrocephalus carries the risk of complications similar to those of intraoperative and immediate postoperative shunt insertion (ie, a 10% risk of infection or hemorrhage, basilar artery injury, and hypothalamic or pituitary dysfunction) but does not carry the long-term problems and complications of shunts and is not associated with overdrainage. However, a rare complication of late rapid deterioration can occur up to 7 years after the surgery and is not well understood but is thought to be a result of stoma scarring. This can result in coma and possible death due to obstructive hydrocephalus.

Leaving an Ommaya reservoir in place can be helpful, especially in patients who are in areas where access to neurosurgical care is limited. Tapping the Ommaya reservoir and aspirating CSF can serve as a bridge to definitive treatment. An element of underdrainage is present even in successful cases because the ventricles remain larger than in shunted patients. The mortality rate of ETV is approximately 1%.

Some adolescents with myelomeningocele and shunted hydrocephalus develop focal discomfort at the shunt valve or along the distal catheter in the posterior triangle of the neck. This had been termed shuntalgia and is characterized by tenderness with a palpable firm fibrotic sheath of scar tissue in the area of pain. This may be related to the adolescent growth spurt and, although resistant to nonsteroidal anti-inflammatory drugs (NSAIDs), is usually self-limiting.

Lastly, 20-40% of children with myelomeningocele have an allergy to latex. Care must be exercised to avoid contact with latex products during surgery and postoperative hospitalization to minimize the risk of anaphylactic reactions.

OUTCOME AND PROGNOSIS

Section 9 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

Shunting has dramatically improved the outcome of patients with hydrocephalus. With careful and systematic treatment and follow-up in the absence of any complex developmental syndrome, patients with hydrocephalus are expected to survive and reach adulthood. Simple aqueductal stenosis is associated with very good outcome, with more than one half of patients are expected to complete normal schooling. Several studies have demonstrated that at least 50-70% of these patients can attain an intelligence quotient (IQ) of higher than 80, which is considered normal. However, in children with hydrocephalus, detailed neuropsychological testing has revealed that performance IQ is poorer than verbal IQ. Repeated shunt infections have been associated with poor outcome. The most severe outcome is associated with posthemorrhagic or postmeningitic hydrocephalus because of the underlying brain damage sustained during the process.

Some children with myelomeningocele develop intellectual impairment. This may be related to hydrocephalus and shunt infection and malfunction. Approximately 80% of children with myelomeningocele have an intelligence within the reference range but have specific learning disabilities, including difficulty with pragmatic communication, short-term memory, executive functioning, and reading comprehension. These children often have what is described as a “cocktail personality” and can be loquacious without any substantial context to their conversations. They also tend to be weaker in the area of perceptual and motor skills. Children with myelomeningocele without hydrocephalus typically have a normal intelligence.

Physical disabilities related to the level of spinal cord damage represent the main problem in children with myelomeningocele. Several studies have shown that the poorest prognosis for motor outcome is associated with thoracic lesions, whereas sacral and lumbar lesions are associated with a better outcome, with some patients having the ability to be community ambulators. Although children with lower lesions may initially function well, approximately 34% of children with myelomeningocele who are considered to be clinically stable develop a decreased mobility status, and many children who are community ambulators require wheelchair assistance by adulthood.

Although shunting is necessary in children with myelomeningocele and hydrocephalus, those who require shunting have been shown to have a shorter lifespan than those who do not. This is likely due to the severity of the lesion and complications of shunting.

The incidence of epilepsy in children with hydrocephalus varies from 7-47%, with the highest prevalence among patients with postmeningitic and posthemorrhagic hydrocephalus caused by the underlying brain parenchyma damage.

Finally, secondary craniosynostosis can develop as a consequence of chronic shunt overdrainage. Children with milder forms who have had differential pressure valves for years develop a thick skull (ie, hyperostosis cranii ex-vacuo). Secondary craniosynostosis is more common in children with myelomeningocele, and the presence of myelomeningocele is believed to result in a state of reduced CSF content in the entire neuraxis, leading to reduced drive for brain development and early suture closure.

FUTURE AND CONTROVERSIES

Section 10 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

A significant effort in research and development is directed at shunt valve design. Although advancements have been achieved in the last 2 decades, improvements can still be made. The 30% failure rate in the first year is regarded as high, but no means to reduce it has been found.

Globally, a significant effort has been made to educate patients and doctors regarding how to diagnose the condition early and how to incorporate a multimodality and multispecialty approach in order to recognize the particular problems that occur in children with hydrocephalus and to improve their care. A significant factor for success involves local organization and follow-up arrangements, as well as improvement of surgical technique. Although simple in concept and  straightforward in functioning, shunts are fraught with pitfalls and difficulties. Much improvement can be made with centralization of services and expertise.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

Media file 1:  The lumbar region of a newborn baby with myelomeningocele. The skin is intact, and the placode-containing remnants of nervous tissue can be observed in the center of the lesion, which is filled with cerebrospinal fluid (CSF).
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Media type:  Photo

Media file 2:  Axial T1-weighted MRI scan of an 8-week-old girl who presented with enlarging head circumference. Considerable ventricular dilatation is shown on the lateral and third ventricles. Periventricular lucency is observed around the frontal horns, indicating raised intraventricular pressure.
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Media type:  MRI

Media file 3:  Sagittal T1-weighted MRI scan of the infant in Image 2. The third and lateral ventricles are dilated, whereas the fourth ventricle is of normal size. Aqueductal stenosis is shown. The appearance is typical of this condition.
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Media type:  MRI

Media file 4:  Phase-contrast MRI scan of the same child in Images 2-3, obtained 3 months after endoscopic third ventriculostomy. A large signal void is shown in the prepontine region, corresponding to the flow through the stoma in the floor of the third ventricle, indicating that the ventriculostomy is functioning well.
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Media type:  MRI

Media file 5:  Axial T1-weighted MRI scan of a 15-year-old girl who was born with thoracic myelomeningocele, hydrocephalus, and Arnold-Chiari II syndrome. She was treated with a ventriculoperitoneal shunt. The ventricular system has a characteristic shape, with small frontal and large occipital horns, which are typical in patients with spina bifida. The shunt tube is shown in the right parietal region.
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Media type:  MRI

Media file 6:  Sagittal T1-weighted MRI scan of the same patient in Image 5. Significant hindbrain hernia and low-lying fourth ventricle are shown in the context of the Arnold-Chiari II syndrome.
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Media type:  MRI

Media file 7:  Damaged shunt valve removed during shunt revision from a 22-year-old woman with hydrocephalus and spina bifida. The material of the valve has dramatically disintegrated.
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Media type:  Photo

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Indications
• Relevant Anatomy
• Contraindications
• Workup
• Treatment
• Complications
• Outcome and Prognosis
• Future and Controversies
• Multimedia
• References

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