Hydrocephalus
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Direct answer
Hydrocephalus is an abnormal accumulation of cerebrospinal fluid within the ventricles, classified as communicating or obstructive. Obstructive types, most often from aqueduct stenosis, are commonly treated with endoscopic third ventriculostomy, whereas communicating types usually need a ventriculoperitoneal shunt. Rapid head growth, a bulging fontanelle and split sutures are the classic infant signs.
What you must remember
- Communicating hydrocephalus: CSF flow is impaired by poor absorption, classically after meningitis or intraventricular haemorrhage in preterm infants.
- Obstructive hydrocephalus: CSF flow is blocked within the ventricular system, most often at the cerebral aqueduct, so the lateral and third ventricles dilate.
- Sunsetting sign: downward deviation of the eyes with upper lid retraction, reflecting raised intracranial pressure.
- Infant signs: rapid occipitofrontal head growth, a tense anterior fontanelle, split sutures and prominent scalp veins.
- Congenital causes: aqueduct stenosis, Dandy-Walker malformation and Chiari malformation.
- Shunt complications: infection, blockage and over-drainage, which can cause slit ventricles and subdural collections.
- Endoscopic third ventriculostomy: creates an opening in the floor of the third ventricle, suited mainly to obstructive types.
Shunt or endoscopic third ventriculostomy
Choosing between a shunt and endoscopic third ventriculostomy depends on the type of hydrocephalus and the child's age. The table compares the two most-tested options.
| Feature | Ventriculoperitoneal shunt | Endoscopic third ventriculostomy |
|---|---|---|
| Mechanism | Diverts CSF to the peritoneum through a valve | Creates an opening in the floor of the third ventricle |
| Best suited to | Communicating hydrocephalus and most infants | Obstructive hydrocephalus such as aqueduct stenosis |
| Main complications | Infection, blockage and over-drainage | Haemorrhage and injury to the hypothalamus |
| Follow-up | Lifelong, with revisions as needed | Shunt-free when successful, with ongoing review |
Obstructive types favour endoscopic third ventriculostomy, because the blocked pathway can be bypassed inside the skull, whereas communicating types need a shunt because CSF absorption is impaired. Infants with a failed endoscopic procedure or a dilated ventricle may still need a shunt, so the decision is individualised by the neurosurgical team.
Where the exam tries to catch you
Hydrocephalus questions often test the link between the type of obstruction and the chosen surgery.
- Trap: choosing a shunt by default for aqueduct stenosis Correct: endoscopic third ventriculostomy is often preferred for obstructive hydrocephalus because it avoids long-term shunt hardware.
- Trap: calling downward gaze deviation a cerebellar sign Correct: the sunsetting sign reflects raised intracranial pressure with lid retraction, not cerebellar dysfunction.
- Trap: assuming split sutures are normal in an infant with rapid head growth Correct: split sutures and a bulging fontanelle indicate raised pressure and need urgent evaluation.
- Trap: ignoring over-drainage in a shunted child with a slit ventricle Correct: over-drainage can cause slit ventricles and subdural collections, so the valve needs neurosurgical review.
Frequently asked questions
What is the sunsetting sign in hydrocephalus?
The sunsetting sign is a downward deviation of the eyes with upper eyelid retraction, reflecting raised intracranial pressure from hydrocephalus. It is commonly seen in infants with a tense fontanelle and in older children with raised pressure from other causes.
What is the most common cause of congenital obstructive hydrocephalus?
Aqueduct stenosis is the commonest cause of congenital obstructive hydrocephalus, and it produces dilatation of the lateral and third ventricles. Dandy-Walker malformation and posterior fossa tumours are other causes that obstruct CSF flow.
When is endoscopic third ventriculostomy preferred over a shunt?
Endoscopic third ventriculostomy is preferred for obstructive hydrocephalus in suitable children, because it can avoid long-term shunt hardware. A ventriculoperitoneal shunt is generally used for communicating hydrocephalus, where CSF absorption is impaired.
Why does a ventriculoperitoneal shunt need long-term follow-up?
A ventriculoperitoneal shunt needs long-term follow-up because its valve can block, become infected or cause over-drainage. Each complication needs prompt neurosurgical review, since its symptoms can mimic raised intracranial pressure.
What are the classic signs of raised intracranial pressure in infants?
Classic signs of raised intracranial pressure in infants include rapid head growth, a bulging anterior fontanelle, split sutures and prominent scalp veins. These signs appear because the skull sutures are still open and can widen under pressure.