Residency · Residency · Neurosurgery

Hydrocephalus in Children: Shunts and Endoscopic Third Ventriculostomy

Overview

Hydrocephalus is an abnormal accumulation of cerebrospinal fluid within the ventricular system that causes ventricular enlargement. It occurs in approximately 1 in 500 to 1000 live births and stands as the most common condition treated by pediatric neurosurgeons. Two main treatment modalities exist: CSF shunting, which diverts fluid to another body compartment, and endoscopic third ventriculostomy, which creates an internal bypass for CSF flow. Choroid plexus cauterization may be added to ETV in selected cases. Despite decades of technological development, shunt failure remains the dominant clinical problem, occurring in approximately 40 percent of patients within the first two years.

Pathophysiology and Classification

CSF Physiology

The brain produces approximately 500 milliliters of CSF per day in adults, at a rate of roughly 0.35 milliliters per minute, with proportionally less in infants. The choroid plexus generates approximately 70 percent of CSF, with the remaining 30 percent arising from the brain interstitium. CSF flows from the lateral ventricles through the foramina of Monro into the third ventricle, then through the aqueduct of Sylvius into the fourth ventricle, and exits via the foramina of Luschka and Magendie into the subarachnoid space. Absorption occurs primarily through arachnoid granulations into the superior sagittal sinus, with additional drainage through glymphatic pathways.

Communicating Hydrocephalus

In communicating hydrocephalus, there is no obstruction within the ventricular system itself. Instead, CSF absorption at the arachnoid granulations is impaired. Common causes include post-hemorrhagic hydrocephalus from intraventricular hemorrhage of prematurity, post-infectious hydrocephalus from meningitis, and subarachnoid hemorrhage. All ventricles are dilated because the obstruction lies beyond the ventricular exits.

Obstructive Hydrocephalus

Obstructive or non-communicating hydrocephalus results from a mechanical blockage within the ventricular system. Common sites of obstruction include the foramen of Monro, which may be blocked by a colloid cyst or tumor; the aqueduct of Sylvius, which may be narrowed by congenital aqueductal stenosis, the most common congenital cause, or compressed by a tectal plate glioma; and the fourth ventricle outlets, which may be occluded by a Dandy-Walker malformation or posterior fossa tumor. Characteristically, ventricles proximal to the obstruction are dilated while those distal remain normal or small.

Etiologies by Age

In neonates, the most common cause is intraventricular hemorrhage of prematurity, followed by congenital aqueductal stenosis, myelomeningocele, and Dandy-Walker malformation. In infants, post-hemorrhagic and post-meningitic causes predominate alongside congenital malformations and tumors. In older children, posterior fossa tumors such as medulloblastoma and ependymoma, aqueductal stenosis, and arachnoid cysts are the leading etiologies.

Clinical Presentation

Infants with Open Fontanelle

Infants present with rapidly increasing head circumference that crosses percentile lines on growth charts. The anterior fontanelle is bulging and tense, and sutures may be splayed with a characteristic "cracked pot" percussion note known as Macewen sign. The sunsetting sign, where the eyes deviate downward from pressure on the tectal plate, is a classic finding. Other signs include irritability, poor feeding, vomiting, and distended scalp veins.

Older Children with Closed Fontanelle

Older children present with headache that is worse in the morning and with coughing or straining, nausea and vomiting particularly in the morning, and papilledema, though this may not be present in acute presentations. Gait disturbance and ataxia, cognitive decline with deteriorating school performance, Parinaud syndrome with upgaze palsy from aqueductal stenosis, and sixth nerve palsy as a false localizing sign are all recognized presentations. Cushing triad with bradycardia, hypertension, and irregular respirations indicates acute decompensation.

Emergency Presentation

Acute obstructive hydrocephalus manifests as rapidly progressive lethargy, vomiting, and obtundation. Shunt malfunction may present with identical acute symptoms. These scenarios require emergent intervention with EVD placement, shunt revision, or ETV.

Diagnostic Workup

Imaging

Ultrasound through the open fontanelle provides non-invasive serial monitoring of ventricular size in neonates, measuring the Evans index and frontal horn dimensions. CT offers rapid assessment of ventricular size without sedation but carries radiation risk that limits serial use. MRI provides the best evaluation of etiology including tumors, malformations, and aqueductal stenosis, and cine-flow sequences can assess aqueductal CSF flow. The Evans index, defined as the ratio of maximum frontal horn width to maximum biparietal diameter, exceeds 0.3 in ventriculomegaly. The frontal-occipital horn ratio, which averages the frontal and occipital horn widths divided by biparietal diameter, is more reliable for serial monitoring.

Head Circumference

Head circumference should be plotted on age-appropriate growth charts. Serial measurements are far more informative than single measurements, and crossing percentile lines is more concerning than a single measurement that happens to be large.

CSF Shunts

Components

A CSF shunt consists of three components. The proximal catheter is placed in the lateral ventricle, either through Kocher's point in the frontal horn, located 1 centimeter anterior to the coronal suture and 2 to 3 centimeters lateral to the midline, or through Frazier's point in the occipital horn, located 6 to 7 centimeters above the inion and 3 to 4 centimeters lateral to the midline. The valve regulates CSF flow through various mechanisms. The distal catheter terminates in the peritoneal cavity most commonly, or alternatively in the right atrium for a ventriculoatrial shunt or the pleural space.

Valve Types

Differential pressure valves open at a set pressure differential and come in fixed-pressure versions such as the Delta valve and programmable versions including the Codman Hakim, Strata, and proGAV valves that can be adjusted externally with a magnetic programmer. Flow-regulated valves such as the Orbis-Sigma limit maximum flow rate. Anti-siphon devices prevent excessive drainage when the patient is upright, and gravitational devices such as the proSA and ShuntAssistant add resistance specifically in the upright position. Programmable valves with integrated antisiphon or gravitational components are increasingly becoming the standard.

Shunt Insertion Technique

The procedure is performed under general anesthesia with the patient supine and head turned. Perioperative antibiotics are given, and many centers use antibiotic-impregnated catheters. The proximal catheter is inserted through a burr hole at Kocher's or Frazier's point, either freehand or with image guidance, targeting the frontal horn with the tip ideally anterior to the foramen of Monro. The catheter is tunneled subcutaneously from the head to the abdomen, where the distal end is placed through a small periumbilical or subcostal laparotomy with 20 to 25 centimeters of catheter in the peritoneal cavity. CSF flow is confirmed from the proximal catheter before connection. Intraoperative ultrasound or navigation can improve catheter placement accuracy.

Ventriculoatrial Shunt

The distal catheter is placed in the right atrium via the internal jugular or facial vein. Indications include peritoneal adhesions, peritoneal infection, or VP shunt failure with peritoneal complications. Specific complications include shunt nephritis from immune complex deposition, cardiopulmonary embolism, and superior vena cava syndrome. The catheter length requires adjustment as the child grows.

Shunt Complications

Shunt Malfunction

Shunt malfunction is the most common complication, with approximately 40 percent failing within two years. Proximal obstruction is the most frequent cause, typically from choroid plexus tissue or debris occluding the catheter. Distal obstruction results from peritoneal adhesions, omental wrapping, or pseudocyst formation. Valve malfunction from mechanical failure or debris, and catheter disconnection or migration at connection sites also occur.

Shunt Infection

Shunt infection occurs at a rate of 5 to 15 percent per procedure. The most common organisms are coagulase-negative Staphylococcus, particularly S. epidermidis, followed by S. aureus. Infections typically manifest within six months of surgery, reflecting contamination at insertion rather than hematogenous seeding. Presentation includes fever, wound erythema, shunt tract tenderness, peritonitis, or meningitis. Diagnosis requires a shunt tap for CSF cell count, culture, glucose, and protein along with serum inflammatory markers.

Treatment involves externalization or removal of the entire shunt system, intravenous antibiotics with vancomycin and ceftriaxone empirically tailored to culture results, serial CSF cultures until negative for typically 48 to 72 hours, and new shunt insertion after CSF sterilization, usually 7 to 10 days later. Prevention strategies include antibiotic-impregnated catheters, perioperative antibiotics, no-touch surgical technique, and reduced operating room traffic.

Overdrainage Syndromes

Slit ventricle syndrome results from chronic overdrainage producing very small ventricles with intermittent headaches as the shunt becomes intermittently occluded. Subdural collections form as the brain collapses away from the inner table. Premature craniosynostosis can occur from chronic overdrainage in infants. Management involves programmable valve adjustment, addition of an antisiphon device, or ETV to achieve shunt independence.

Abdominal Complications

Pseudocysts are CSF collections walled off by peritoneum that may be sterile or infected. Bowel perforation is rare. Inguinal hernia or hydrocele can develop from CSF tracking into the processus vaginalis in infants.

Endoscopic Third Ventriculostomy

Principle

ETV creates a stoma in the floor of the third ventricle, allowing CSF to bypass a distal obstruction, typically aqueductal stenosis, and flow directly into the prepontine cistern. This provides a shunt-free treatment that avoids all hardware-related complications.

Indications

The primary indication is obstructive non-communicating hydrocephalus. Aqueductal stenosis represents the ideal indication with the highest success rates. Posterior fossa tumors causing obstructive hydrocephalus are also excellent indications. ETV can be attempted in post-hemorrhagic or post-infectious hydrocephalus but with lower success rates.

ETV Success Score

The ETVSS predicts the likelihood of ETV success based on three factors: age, with infants under one month having the worst prognosis and those over 10 years having the best; etiology, with aqueductal stenosis being most favorable and post-infectious causes least; and prior shunt status, with no prior shunt being more favorable. The score ranges from 0 to 90, with higher scores indicating greater likelihood of success. An ETVSS above 70 identifies strong ETV candidates, below 40 suggests ETV is unlikely to succeed and a shunt should be considered, and scores of 40 to 70 represent a judgment call requiring shared decision-making with families.

Surgical Technique

Under general anesthesia with the patient supine and head elevated, a burr hole is placed at Kocher's point, typically on the right side. A rigid neuroendoscope is inserted into the right lateral ventricle and navigated through the foramen of Monro into the third ventricle. Key landmarks are identified: the mammillary bodies posteriorly, the infundibular recess anteriorly, and the basilar artery visible beneath the floor. The fenestration is created in the tuber cinereum just anterior to the mammillary bodies and posterior to the infundibular recess using a blunt trocar, balloon dilation, or bipolar cautery. Patency is verified by observing pulsatile flow and visualizing the prepontine cistern and basilar artery through the stoma. The stoma is enlarged with a Fogarty balloon to reduce the risk of closure.

ETV Complications

Basilar artery injury is catastrophic but rare at less than 1 percent. Intraventricular hemorrhage, transient fever, and diabetes insipidus from hypothalamic manipulation can occur. Stoma closure occurs in 10 to 20 percent of cases, requiring repeat ETV or shunt placement. Most failures occur within six months, though late failures are possible. CSF leak is an additional risk.

ETV with Choroid Plexus Cauterization

ETV/CPC combines the third ventriculostomy with cauterization of the choroid plexus in both lateral ventricles. By reducing CSF production, it augments the effect of the ETV. Pioneered by Dr. Benjamin Warf in Uganda for infant hydrocephalus, this technique extends ETV applicability to younger infants and those with communicating hydrocephalus. Evidence shows improved success rates in infants compared to ETV alone, particularly when the ETVSS is below 70. The technique uses a flexible endoscope to systematically cauterize choroid plexus bilaterally, with success correlating to completeness of cauterization, targeting greater than 90 percent ablation. Some controversy exists regarding the additional benefit of CPC, with ongoing multicenter trials including the International Infant Hydrocephalus Study investigating this question.

Shunt vs. ETV

ETV is preferred for obstructive hydrocephalus, age greater than six months, ETVSS above 70, and aqueductal stenosis. Shunting is preferred for communicating hydrocephalus, age under six months unless ETV/CPC is considered, ETVSS below 40, and failed ETV. Many patients fall into intermediate categories requiring shared decision-making with families. ETV offers the advantages of shunt independence, no hardware, and no risk of shunt malfunction or infection, but carries the disadvantages of possible delayed failure, lack of universal effectiveness, and the rare but serious risk of basilar artery injury. No definitive randomized controlled trial has compared ETV versus shunt across all age groups and etiologies.

Post-Hemorrhagic Hydrocephalus of Prematurity

Intraventricular hemorrhage occurs in 20 to 25 percent of very low birth weight infants. Post-hemorrhagic ventricular dilation develops in 25 to 50 percent of those with grade III or IV IVH. Temporizing measures include serial lumbar punctures, ventricular access devices or reservoirs, and ventriculosubgaleal shunts. Definitive shunt placement is deferred until the infant reaches 2 to 2.5 kilograms, CSF protein falls below 1.5 grams per liter, and no active infection is present. The DRIFT trial investigating early drainage, irrigation, and fibrinolytic therapy showed some benefit but increased secondary hemorrhage. Optimal timing of definitive treatment remains an active area of research.

<image>Intraoperative endoscopic photograph during endoscopic third ventriculostomy (ETV) showing the view through the neuroendoscope of the floor of the third ventricle with the mammillary bodies posteriorly and the infundibular recess anteriorly, with the fenestration being created in the tuber cinereum and the basilar artery visible through the transparent floor beneath the stoma</image>

<image>Sagittal T2-weighted MRI of the brain in an infant with obstructive hydrocephalus due to aqueductal stenosis, demonstrating massive dilation of the lateral and third ventricles, a distended floor of the third ventricle bowing inferiorly, and a normal-sized fourth ventricle, with thinned cortical mantle</image>

<image>Lateral skull radiograph of a child with a ventriculoperitoneal shunt in situ, showing the proximal catheter in the right frontal horn, the shunt valve behind the right ear, and the distal catheter coursing subcutaneously down the neck and chest into the peritoneum, demonstrating proper catheter positioning</image>

<image>Cranial ultrasound through the anterior fontanelle in a premature infant with post-hemorrhagic hydrocephalus, coronal view demonstrating bilateral lateral ventricular dilation with echogenic intraventricular blood products in the occipital horns and germinal matrix hemorrhage residua</image>

Clinical Pearls

Approximately 40 percent of shunts fail within the first two years; shunt malfunction should always be considered in any child with a shunt presenting with headache, vomiting, or lethargy. A shunt series consisting of skull and abdomen radiographs can identify catheter disconnection or migration, but a normal shunt series does not rule out malfunction; CT or rapid MRI should be obtained when clinical suspicion is high. The ETVSS is the best validated tool for predicting ETV success and should be used to guide treatment discussions with families. Antibiotic-impregnated catheters containing rifampin and clindamycin reduce infection rates by approximately 50 percent and should be used routinely. ETV is most successful for aqueductal stenosis in children older than two years, with success rates exceeding 80 percent in this population. In premature infants with post-hemorrhagic hydrocephalus, definitive shunt placement should be deferred until CSF protein has decreased and the infant has grown; temporizing with ventricular access devices bridges this period. Programmable valves should be rechecked after MRI because magnetic fields can reset the valve setting. Choroid plexus cauterization as an adjunct to ETV may benefit infants who would otherwise have a low ETV success rate, but evidence is still evolving.

References

1. Kulkarni AV et al. Endoscopic third ventriculostomy in the treatment of childhood hydrocephalus. J Pediatr. 2009;155(2):254-259.
2. Warf BC. Comparison of endoscopic third ventriculostomy alone and combined with choroid plexus cauterization in infants younger than 1 year of age. J Neurosurg Pediatr. 2008;1(5):405-412.
3. Drake JM et al. Randomized trial of cerebrospinal fluid shunt valve design in pediatric hydrocephalus. Neurosurgery. 1998;43(2):294-305.
4. Kulkarni AV et al. Endoscopic third ventriculostomy vs cerebrospinal fluid shunt in the treatment of hydrocephalus in children: a propensity score-adjusted analysis. Neurosurgery. 2010;67(3):588-593.
5. Limbrick DD et al. Neurosurgical treatment of progressive posthemorrhagic ventricular dilation in preterm infants. J Neurosurg Pediatr. 2016;17(3):298-305.

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