Hydrocephalus
The 5 Minute Pediatric Consult
Peter M. Bingham
DEFINITION
Hydrocephalus is accumulation of cerebrospinal fluid in the ventricles, leading to their enlargement.
CAUSES
- Developmental
- Chiari malformation type II (inferior displacement of medulla and cerebellum)
- Primary aqueductal stenosis
- Dandy-Walker malformation (absence of cerebellar vermis, small cerebellar hemispheres, enlarged posterior fossa, often with cystic fourth ventricle)
- Tumors of any histologic type located near foramina or the aqueduct
- Infection (meningitis) can lead to leptomeningeal adhesions and granulations.
- Hemorrhage (usually grade III to IV intraventricular hemorrhage or trauma-related) may result in a blood clot, meningeal adhesions, or granular ependymitis.
PATHOPHYSIOLOGY
- Normal pathway of CSF: choroid plexus, lateral ventricles, foramina of Monroe, third ventricle, aqueduct of Sylvius, fourth ventricle, foramina of Lushka and Magendie, subarachnoid space, arachnoid granulations, venous circulation
- Hydrocephalus often involves obstruction to CSF flow, even in the rare case of choroid plexus papilloma (overproduction of CSF).
- Noncommunicating hydrocephalus: The obstruction is in the ventricular system.
- Communicating hydrocephalus: The obstruction is outside of the ventricular system.
- Although the noncommunicating/communicating distinction has traditionally been fundamental in the literature, it has no prognostic significance; the value of the distinction concerns choice of a site for palliative drainage, and etiologic considerations.
COMPLICATIONS
- Acute hydrocephalus
- Herniation of temporal lobes may be fatal.
- Chronic hydrocephalus
- Macrocephaly
- Spastic paraparesis may lead to gait and motor problems.
- Developmental delay
- Other causes of macrocephaly:
- Familial macrocephaly
- Pericerebral effusions
- Congenital anomalies of intra- or extracerebral veins
- Achondroplasia
- Tumors, intracranial cysts
- Neurocutaneous syndromes
- Dysmorphic syndromes
- Primary megalencephaly
- Some leukodystrophies
- GM2 gangliosidosis
- Mucopolysaccharidoses
- Head-sparing intrauterine growth retardation (relative macrocephaly)
- Rapid catch-up growth following prolonged malnutrition
- Other causes of ventriculomegaly include brain atrophy and chronic ethanol or corticosteroid exposure (reversible)
- In benign external hydrocephalus, both the ventricles and extraaxial CSF spaces are proportionately enlarged, and macrocephaly is common.
HISTORY
- Hydrocephalus is more common in preterm neonates in the intensive care nursery.
- Infants and children may also present to the primary pediatrician with new-onset hydrocephalus.
- Concerning complaints, especially in infants, include:
- Behavioral changes
- Enlarging head
- Nausea and vomiting
- Vital signs: The Cushing triad (hypertension, bradycardia, respiratory irregularities), which is characteristic of increased intracranial pressure, may be present in acute hydrocephalus.
- HEENT: Increasing head circumference in infants, sometimes with a bulging fontanelle; transillumination of the skull (using an intense light source) is seen in severe hydrocephalus; specificity of MacEwan “cracked pot” head percussion note is uncertain.
- Mental status: irritability in infants, behavioral changes in children
- Cranial nerves: Parinaud syndrome (setting sun sign, paralysis of upward gaze), papilledema or optic atrophy, visual changes
- Motor: spastic paraparesis in chronic hydrocephalus
- Reflexes: increased in chronic hydrocephalus
TESTS
Imaging
- Head ultrasound
- Standard screening test for neonates with suspected hydrocephalus or intraventricular hemorrhage
- The anterior fontanelle must be patent for this test.
- Shows size of ventricles and presence or absence of blood
- Computed tomography (CT)
- Mainly used in infants and children whose anterior fontanelles have closed
- Advantage compared to ultrasound: better visualization of fourth ventricle/brainstem, calcifications
- Magnetic resonance imaging (MRI)
- Definitive test for analyzing brain anatomy
- Can identify developmental malformations such as Chiari and Dandy-Walker
Neurosurgeons’ use of therapeutic lumbar or ventricular puncture has decreased in recent years. These procedures must be weighed against risk of herniation (decreased when sutures are open).
VENTRICULAR SHUNT
- Indication: symptomatic progressive hydrocephalus
- Contraindications: active central nervous system infection, active intraventricular hemorrhage, and poor overall prognosis
- Components: ventricular catheter, reservoir (target of “shunt taps”), valve, distal catheter
- Distal sites: The peritoneum is the safest choice; the gall bladder, pleura, ureter, and right atrium are other choices.
- Siphon effect: drop in ventricular pressure on sitting or standing, alleviated in newer shunt systems, such as the Delta shunt, by anti-siphon devices that close the valve when there is excessive negative pressure in the distal catheter
- Complications: Obstruction and infection are the main complications and often coincide, requiring replacement of the shunt system, ideally after any infection has been cleared.
- Rarely, shunting may be followed by acute decompensation, which may be due to upward transtentorial herniation of the brainstem.
THIRD VENTRICLE FENESTRATION
- Background: An old procedure that has fallen out of favor with development of modern shunt systems
- Current status: New endoscopic techniques make this procedure useful in rare cases of isolated intraventricular obstruction.
- When the etiology or need for shunt placement may not be clear, it is important to follow clinical status, head circumference, and ventricular size (by head ultrasound or CT).
- Chronic hydrocephalus is often accompanied by spastic paraparesis, visual problems, and developmental delay.
- Most important interventions are supportive, including physical therapy, occupational therapy, and orthopedic therapies for spasticity; interdisciplinary cerebral palsy clinics can be critical in providing easy access to these resources. Special education programs may be appropriate for children with severe developmental delay.
PITFALLS
- It is important for long-term patients in intensive care nurseries to have head circumferences recorded at least once a week. Macrocephaly is not always obvious on visual inspection.
- Papilledema is a sign of increased intracranial pressure, but its absence does not rule out this possibility.
- Head CT often will not show developmental malformations that may accompany hydrocephalus. MRI is the imaging procedure of choice.
- Timing of shunt placement is critical. A shunt placed too early may become infected or obstructed, while waiting too long may worsen permanent brain damage.
| COMMON QUESTIONS AND ANSWERS |
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Q: When does an infant need a head ultrasound?
A: Preterm infants below a certain gestational age or birth weight (varies from hospital to hospital) should all receive screening head ultrasounds while in the intensive care nursery, as well as any infant (inpatient or outpatient) whose head circumference crosses two percentile lines on the growth chart.
Q: When should an infant or child receive an MRI first rather than an ultrasound or CT?
A: Ordering an MRI first is reasonable in outpatients in whom the suspicion of hydrocephalus is strong and there are no obvious causes, such as infection or hemorrhage.
Q: What is the work-up for shunt obstruction and shunt infection?
A: Symptoms and signs of increased intracranial pressure should lead to a neurosurgical evaluation, head CT (to assess ventricular size and placement of ventricular catheter), and shunt series (plains films of the entire shunt system to check for disruptions). Fever is the most important indication for a shunt infection evaluation (shunt tap with CSF cell count, protein, glucose, Gram stain, and culture). Often patients will be evaluated for both complications.
ICD-9-CM 741.0
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Guertin SR. Cerebrospinal fluid shunts: evaluation, complications, and crisis management. Pediatr Clin North Am 1987;34:203–217.
Turner MS. The treatment of hydrocephalus: a brief guide to shunt selection. Surg Neurol 1995;43:314–323.
Wilkins RH, Rengachary SS, eds. Neurosurgery, 2nd ed. New York: McGraw-Hill, 1996.
Copyright © 2000 Lippincott Williams & Wilkins
M. William Schwartz, Louis M. Bell, Jr., Peter M. Bingham, Esther K. Chung, David F. Friedman and Andrew E. Mulberg, The 5 Minute Pediatric Consult