Spina Bifida Family Support

"Families Helping Families"



Information derived from EMedicine.com. Author:Spyros Sgouros, MD, FRCS(SN)(Glasg), Senior Lecturer, Department of Neurosurgery, Division of Neuroscience, Section of Pediatrics, University of Birmingham, England

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

Infantile hydrocephalus can be associated with congenital anomalies, such as aqueduct stenosis, spina bifida, and Arnold-Chiari malformation; it can also be associated with less common conditions, such as Dandy-Walker syndrome and encephaloceles. Of these, the most frequent is aqueduct stenosis. It can be associated with acquired conditions such as perinatal intraventricular hemorrhage and meningitis. It can also occur after closed head injury.

History of the Procedure: In the 1960s, 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 receive operation for hydrocephalus reached adulthood. Furthermore, the children who did survive had a 50% chance of remaining permanently brain damaged. After the introduction of shunting, outcomes improved. Currently, if appropriate care of the shunt has occurred, most children with hydrocephalus reach adulthood. In a 20-year follow-up survey of children who received shunting in the 1970s, more than half of them graduated from normal schools.

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 at 20 years. Most of the deaths occurred in the first year of life, mostly because of renal and respiratory problems associated with the 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 in the first year of life, from causes not related to hydrocephalus but to the spina bifida. In a recent survey of adults with spina bifida, 6% of patients died because of shunt-related problems or after craniovertebral decompression for Chiari malformation.

Problem: Hydrocephalus can be caused by increased production of CSF or impaired circulation and absorption. Hydrocephalus caused by impaired circulation is called obstructive hydrocephalus because an anatomic block to CSF circulation is present. Hydrocephalus caused by increased production or impaired absorption is called communicating hydrocephalus because no anatomic block to CSF circulation exists. According to some authorities, all cases of hydrocephalus are obstructive, ie, the cases 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 for this group are 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.

The incidence of myelomeningocele ranges from 0.2-2 per 1000 live births, with regional and racial variations. The overall incidence of myelomeningocele has declined significantly 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%. No obvious correlation between the level of the lesion and the presence of hydrocephalus has been shown.

Etiology: The simplistic distinction of obstructive and communicating hydrocephalus is historically related to the different conditions that are causing or are associated with impairment of CSF circulation. Examples of conditions with obstructive hydrocephalus are congenital aqueduct 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 are spina bifida, intraventricular hemorrhage, meningitis, and head injury. The distinction between obstructive and communicating hydrocephalus sometimes cannot be made because an element exists of both mechanisms operating.

Pathophysiology: Production of CSF is an active process at a rate of 0.35 mL/min. Absorption of CSF at the arachnoid granulations also is 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 in adults or 250 mL in children of CSF are produced and absorbed. At any given time, a total of 140 mL for adults or 70 mL for children of CSF exists inside the head. Normal CSF pressure inside the ventricles is 110 mm of water pressure. When an impairment of CSF circulation exists, the resulting CSF accumulation leads to ventricular enlargement and 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 used, rapid deterioration follows because of raised intracranial pressure.

In children with aqueduct stenosis, the aqueduct of Sylvius is narrower than usual or is completely occluded, and an obstruction to CSF flow is present. A debate exists whether the aqueduct stenosis is the primary deformity, which leads to ventriculomegaly, or whether the ventriculomegaly is the primary deformity (because of altered abnormal ventricular wall compliance), which leads to secondary aqueduct stenosis caused by continuing compression of the midbrain.

In children with myelomeningocele, several factors are implicated in the pathogenesis of hydrocephalus, including the Chiari type II malformation, a degree of aqueduct stenosis, anomalous venous drainage in the posterior fossa caused by compression of the sigmoid sinuses, the open myelomeningocele, and the presence of other CNS malformations

In the context of the Chiari type II malformation, extensive deformity of the posterior fossa and its structures exists. 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 significant prolapse of the cerebellar tonsils is present through the foramen magnum. All these anatomic factors contribute to the impairment of CSF circulation.

The development of hydrocephalus is temporally related to the closure of the myelomeningocele. In a small proportion 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.

The development of hindbrain hernia during gestation is believed to be caused by the progressive caudal migration of the hindbrain in association with the low-pressure conditions that the open myelomeningocele creates in the spine. Continued loss of CSF soon after birth results in further deterioration of 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 region of the foramen magnum. The neurologic state usually improves after ventricular shunting. In most patients, ventriculomegaly develops gradually within the first few weeks or months of life.

The incidence of hydrocephalus was decreased from 91% to 59% in the small number of children who underwent intrauterine repair of the myelomeningocele compared to historic control subjects who had traditional treatment. The incidence of hindbrain hernia present at birth in this group of children was considerably smaller than that in historic control subjects. Therefore, the lower incidence of hydrocephalus was postulated to be caused by the absence of the obstructing effect of the hindbrain hernia at the level of the foramen magnum to the flow of CSF. However, a variety of factors certainly are implicated in this mechanism.

In children with postmeningitic or posthemorrhagic hydrocephalus, the arachnoid granulations are occluded by protein (meningitis) or blood degradation products (intraventricular hemorrhage), rendering CSF absorption relatively ineffective.

Clinical: Infants with hydrocephalus develop enlarging head with bulging fontanelle, enlarged scalp veins, macrocrania, suture diastasis, and positive Macewen (ie, cracked-pot) sign. If left untreated, these infants develop sunset eyes, recurrent vomiting, and later, respiratory arrest.

The particular consideration of children with myelomeningocele is the presence of hindbrain hernia in the context of the Arnold-Chiari malformation, which can cause early clinical symptoms of bulbar palsy and can remain unnoticed by inexperienced observers. Poor feeding, recurrent vomiting, poor sucking, generally subdued behavior with poor crying, high-pitched cry or stridor caused by vocal cord paralysis, episodes of apnea, and recurrent aspiration (often manifesting with recurrent pneumonia) can all be manifestations of brain stem dysfunction caused by hindbrain hernia and aggravated by ventricular dilatation. Lastly, 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.

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 caused by respiratory arrest.

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. In contrast, children with mild or moderate ventriculomegaly and head circumference within the reference range may not require initial treatment. In these children, an observation policy can be adopted for the first few months of life, and monitoring of the head circumference and repeat ultrasound, CT, or magnetic resonance (MR) scanning are helpful to decide whether shunting is finally required.

A significant consideration for timing of treatment is the child's age, prematurity status, and weight. As a general rule, shunting is avoided, if possible, in children younger than 6 months because they have an increased risk of infection. For the same reason, in premature babies weighing less than 1 kg, deferring shunting, if possible, until they have gained weight is best. These considerations often arise in children with posthemorrhagic hydrocephalus, who often are premature and small-for-dates.

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

In children with intraventricular hemorrhage, although active hydrocephalus may have been present early in life, contemplating shunting is often difficult because the CSF is heavily blood stained and/or the protein content is too high (>1 g/dL). In such cases, the traditional attitude is to insert an external ventricular drain for a period until the CSF clears and a shunt can be inserted. Efforts to accelerate the clearance of blood from the CSF have been made by injecting streptokinase in the ventricles, with moderate success. This therapeutic maneuver still has not 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. Patients are sometimes observed with the typically shaped ventricles of hydrocephalus that are caused by spina bifida but do not appear to have tension, with no periventricular lucency, and with no symptoms (eg, headache, drowsiness, diplopia, bulbar features) suggesting active hydrocephalus. If these patients never receive shunting, serial monitoring with intelligence and psychometric testing should be undertaken.

If a patient has no clinical symptoms and their psychometric test results indicate stability, the neurosurgeon should be discouraged from contemplating shunting solely on the basis of radiologic appearances, keeping in mind that these patients have a high risk of bilateral subdural hematomas. In a similar manner, in patients who already have received shunting, caution should be exercised for considering any intervention on the shunt. Because shunts may be disconnected or appear to not have been working for years, 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 surrounding 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 actually are functioning, and any attempt to remove them without instituting any alternative means of CSF drainage (eg, third ventriculostomy) may be lethal. In contrast, if subtle symptoms or clear measured intellectual decline is present, treatment should be offered. In such cases, patients who have not received shunting should be shunted, and those who have shunts should have their shunts revised.

Relevant Anatomy: 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. Hence, in aqueduct stenosis, dilatation of the lateral and third ventricles is present, but not of the fourth ventricles. 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: Relative contraindications to treatment of infantile hydrocephalus include the presence of severe CNS malformation that is 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; in these cases, neonatologists prefer to counsel parents against treatment of hydrocephalus. The same considerations are applied to severe cases of intraventricular hemorrhage, in which radiologic investigations clearly indicate that significant large parts of the brain have been damaged from the hemorrhage.

Imaging Studies:

Medical therapy: No medical treatment is available that can counteract the accumulation of CSF in the brain. In cases in which a decision has been made not to treat the hydrocephalus, medical treatment is exclusively palliative.

Surgical therapy: In most cases, surgical treatment of hydrocephalus consists of insertion of a ventricular shunt. 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, although, for difficult cases with other coexisting abdominal problems, other options are available, such as the right atrium, the gall bladder, the ureter, or the bladder. 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 currently are in the market. A significant controversy regarding shunts is the design of the valve. Essentially 2 types of shunts exist, the pressure-regulating shunt and the flow-regulating shunt. The pressure-regulating shunts are designed to maintain a difference of pressure between their inlet and outlet, and they allow flow of CSF once that preset pressure has been reached. The flow-regulating shunts are designed to allow a constant flow of CSF, simulating the normal flow of CSF. Despite different designs, large randomized trials have been unable to demonstrate differences between the various types. Different types of valves are seemingly associated to different types of complications—the differential pressure valves are more prone to cause overdrainage complications, whereas the flow regulating valves are more prone to valve obstruction.

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

Third ventriculostomy has been employed recently as a primary treatment of hydrocephalus in children with myelomeningocele, with reported success rates at 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 they do not have fully developed subarachnoid spaces.

Endoscopic third ventriculostomy can be used in children who already have received shunting and present with shunt malfunction at an older age; the reported success rate is approximately 50%. In such circumstances, following third ventriculostomy, and especially if the shunt has been removed, an external ventricular drain should be employed for the first few days to allow emergency decompression if the third ventriculostomy does not function adequately and the patient deteriorates rapidly.

Preoperative details: Appropriate consideration must be given to anesthetic factors, 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 operative treatment is required. Because the actual magnitude of the surgery is not extensive, no problem of circulating blood volume usually exists, and no blood transfusion is likely to be necessary during shunt insertion or endoscopic ventriculostomy, unless a preexisting problem is present.

Intraoperative details: In most cases, shunt insertion involves making a posterior parietal or frontal burr hole through a small linear or curved skin incision. Entry into the peritoneal cavity occurs through a small linear incision either in the upper midline epigastric region or in the right upper quadrant. Advancement of the distal tube from the cranial to the abdominal wound is performed using a purpose-designed tubular dissector advanced in the subcutaneous fat. In the typical case, if a posterior parietal burr hole has been performed, the shunt valve ends up situated behind the ear and usually is easily palpable by the patient and parents. Administering prophylactic antibiotics, usually cephalosporin or vancomycin, is common at the commencement of the operation to lower the shunt infection rate.

In children born with open spina bifida in which shunting is performed simultaneously with myelomeningocele closure, additional precautions should be taken to maintain sterility of the surgical fields. Most neurosurgeons prefer to close the myelomeningocele first 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.

Endoscopic third ventriculostomy is traditionally performed through a frontal burr hole situated just anteriorly to the coronal suture. A rigid or flexible endoscope is preferred. Perforation of the floor of the third ventricle is achieved using a purpose-designed monopolar diathermy with retractable tip or another similar purpose-designed dissector. After formation of the stoma, dilating it using some kind of purpose-designed balloon dilator is common.

Perforation of the floor of the third ventricle is the most delicate and important phase because risk of perforation of the adjacent basilar artery exists. Endoscopic third ventriculostomy can be particularly difficult in children with myelomeningocele because the ventricular anatomy often is unusual or abnormal, the floor of the third ventricle is thicker and more difficult to penetrate, the size of the third ventricle is smaller than in children with aqueduct stenosis, or the septum pellucidum is absent, which can lead in disorientation of the inexperienced operator. In general, inexperienced operators should avoid endoscopic third ventriculostomy 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 clouding the operative field.

In cases of shunt revision or shunt removal after successful ventriculostomy, remember that rupture of the choroid plexus during retrieval of the ventricular catheter is not uncommon, and it can lead to life-threatening hemorrhage. Different techniques can be used to avoid it; the most common of which is to insert a stylet in the catheter lumen and coagulate with the diathermy before retrieving the catheter.

Postoperative details: After successful completion of shunt insertion, or revision, when a differential pressure valve has been implanted, avoiding elevation of the child in the upright position is common to prevent shunt overdrainage and formation of subdural hematomata. In contrast, when a flow-regulating shunt has been implanted, elevating the child to at least 30° the day after is common to promote CSF drainage. To what extent these practices make a difference is unclear. Feeding of very young babies can commence soon after operation.

In cases of shunt revision in older children, recovery tends to be fast, and patients are usually discharged home a few days after operation.

Follow-up care: Postoperative follow-up a few weeks after operation usually is necessary to ensure that wound healing is progressing well and that the head circumference is decreasing accordingly. Performing a CT scan before discharge from the hospital 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 cases of third ventriculostomy, MR scanning with phase-contrast sequence is mandatory to verify patency of the stoma. Customarily, some surgeons perform yearly scanning, but the use of such routines is not universally accepted.

Currently, no satisfactory means exist to detect shunt malfunction before it manifests clinically. Some attempts to visualize CSF flow using ultrasonography or other imaging techniques have not been met with universal acceptance because they are associated with a percentage of false-negative and false-positive results.

Spina bifida requires ongoing follow-up for life because problems unrelated to hydrocephalus appear at various stages and need treatment. Patients with spina bifida have continuing urologic problems because of neuropathic bladder, usually requiring intensive medical and surgical treatment. Orthopaedic problems, such as scoliosis and foot deformities, also require careful follow-up because they are likely to require surgical treatment.

The patient and the doctor must have an ongoing commitment to manage the complications associated with shunting. Shunt complications can be divided into categories as mechanical, infective, and overdrainage-related. As many as 80% of shunts develop mechanical complications at some stage, and one third of these complications occur within the first year of shunt placement. On average, each patient is likely to have 2-3 operations throughout childhood for shunt revision.

Infective complications occur in 5-10% of all shunt operations and are more frequent in younger patients, especially in those younger than 6 months. Most shunt infections manifest in the first 3 months after insertion. 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 a significant proportion of shunt revision operations, up to 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.

During the 1970s, when ventriculoatrial shunts were commonly used, an appreciable number of patients experienced bacterial endocarditis and shunt nephritis caused by direct bacteremia from colonization of the shunt lumen by bacteria. The change from ventriculoatrial to ventriculoperitoneal shunts decreased complications of shunting substantially.

A significant late complication has been the fracture or destruction of shunt tube caused by material degradation and fatigue. Common locations for distal tube fracture are 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 for a time. Late chronic overdrainage leads to the development of slit ventricle symptom. It 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 that is in the distal tube. Chronic overdrainage leads to collapse of the ventricles and intermittent shunt obstruction. Antisiphon devices of different types have been developed to overcome the problem of 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 is associated with the risk of similar intraoperative and immediate postoperative complications as shunt insertion, namely a 10% risk of infection or hemorrhage, but it does not carry the long-term problems and complications of shunts and is not associated with overdrainage. An element of underdrainage is present even in successful cases because the ventricles remain larger than in shunted patients.

Shunting has improved the outcome of patients with hydrocephalus dramatically. In the absence of any complex developmental syndrome, and with careful and systematic treatment and follow-up, patients with hydrocephalus are expected to survive and reach adulthood. Simple aqueduct stenosis is associated with very good outcome, with more than half of the patients expected to complete normal schooling. Several studies have demonstrated that at least 50-70% of these patients can attain an intelligence quotient (IQ) higher than 80, which is considered normal.

Children with spina bifida are expected to have normal intellectual abilities, with the main problems caused by the physical disabilities related to the level of spinal cord damage due to the myelomeningocele. Several studies have shown that the poorest prognosis for motor outcome is associated with thoracic lesions, whereas cervical and lumbar lesions are associated with a better outcome, with patients usually ending up independently mobile. Children with myelomeningocele without hydrocephalus have normal intelligence. Of all types of hydrocephalus, the most severe outcome is associated with posthemorrhagic or postmeningitic hydrocephalus. This is because of the underlying brain damage sustained during the process.

On detailed neuropsychological testing performed in children with hydrocephalus, the performance IQ has been shown to be poorer than verbal IQ. Repeated episodes of shunt infections have been shown to be associated with poor outcome.

Incidence of epilepsy in children with hydrocephalus varies from 7-47%, the worst being postmeningitic and posthemorrhagic hydrocephalus caused by the underlying brain parenchyma damage.

A consideration specific to hydrocephalus related to myelomeningocele is the observation of a high incidence of precocious puberty among female patients, up to 16%. The potential mechanism has implicated hypothalamic dysfunction caused by congenital deformity of the midbrain. Precocious puberty does not appear to have any impact on intellectual development.

In all forms of hydrocephalus, continuous careful monitoring is required for shunts because, at 10 years, up to 80% of them require revision because of some form of failure.

Secondary craniosynostosis can develop as a consequence of chronic shunt overdrainage. Certainly, in a milder form, children who have had differential pressure valves for years develop thick skull (ie, hyperostosis cranii ex-vacuo). Secondary craniosynostosis occurs more often in children with myelomeningocele, and the presence of myelomeningocele has been postulated to result in a state of reduced CSF content in the entire neuraxis, leading to reduced drive for brain development and early suture closure.

Another 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 balance.

Significant effort in research and development is directed at shunt valve design. Although significant advancements have been achieved in the last 2 decades, room for improvement still exists. The failure rate of 30% in the first year is regarded as high, but no means to reduce it presently exist.

Significant effort is made globally to educate parents and doctors to diagnose the condition early and to neurosurgeons to appreciate the particular problems that occur in children with hydrocephalus to improve their care. A significant factor for success lies with local organization and follow-up arrangements, as well as improvement of surgical technique. General neurosurgeons have a tendency not to assign adequate significance to shunt surgery because it is regarded as technically simple. Much improvement can be achieved with centralization of services and expertise.

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