Surgery chapters
Hydrocephalus
Obstructive and communicating hydrocephalus, causes in children and adults, presentation in infants and adults, CSF diversion with EVD, VP shunt and endoscopic third ventriculostomy, shunt complications, normal pressure hydrocephalus and idiopathic intracranial hypertension.
- Hydrocephalus is too much CSF with enlarged ventricles: obstructive (block inside the ventricles, e.g. aqueduct stenosis, tumour) or communicating (poor absorption at the arachnoid villi, e.g. after meningitis or SAH).
- Acute obstructive hydrocephalus is an emergency: treat with an external ventricular drain; long term use a VP shunt or endoscopic third ventriculostomy.
- Normal pressure hydrocephalus = gait disturbance, urinary incontinence, dementia with big ventricles and normal LP pressure; it is a reversible dementia.
On this page
Overview
Hydrocephalus is an increase in CSF volume with dilated ventricles, usually causing raised intracranial pressure. It almost always results from either a block to CSF flow or a failure of CSF absorption; overproduction is rare.
It is common in Pakistani neurosurgical practice because of neural tube defects, tuberculous and bacterial meningitis, and posterior fossa tumours in children. This chapter builds on the CSF physiology in the raised ICP chapter.
Quick physiology recap
- CSF is made by the choroid plexus (about 20 mL/hour; total volume about 150 mL).
- Flow: lateral ventricles → foramen of Monro → third ventricle → aqueduct → fourth ventricle → foramina of Magendie and Luschka → subarachnoid space.
- Absorbed by the arachnoid villi into the superior sagittal sinus.
Classification and causes
| Type | Mechanism | Causes |
|---|---|---|
| Obstructive (non-communicating) | Block within the ventricular system; ventricles above the block dilate | Aqueduct stenosis, posterior fossa tumours (medulloblastoma, ependymoma, pilocytic astrocytoma), colloid cyst of the third ventricle (blocks both foramina of Monro), pineal tumours, Chiari II and Dandy-Walker malformations, intraventricular blood clot, tuberculoma, cysticercal cyst |
| Communicating | CSF leaves the ventricles but is not absorbed; all ventricles dilate | After subarachnoid or intraventricular haemorrhage (including preterm babies), after meningitis (especially tuberculous), raised CSF protein (some spinal tumours), venous sinus thrombosis |
| Overproduction (rare) | Too much CSF | Choroid plexus papilloma or carcinoma |
| Ex vacuo (not true hydrocephalus) | Brain shrinks; ventricles enlarge passively; normal pressure | Atrophy, old infarcts, dementia |
Aqueduct stenosis is the commonest cause of congenital obstructive hydrocephalus. CT/MRI shows big lateral and third ventricles with a normal-sized fourth ventricle.
Do not confuse ventricular enlargement from brain atrophy (hydrocephalus ex vacuo) with true hydrocephalus. In atrophy, the sulci are also wide and the pressure is normal.
Congenital malformations linked with hydrocephalus
- Chiari II malformation: cerebellar vermis and tonsils pushed through the foramen magnum; almost always with myelomeningocele (see the spinal dysraphism chapter).
- Dandy-Walker malformation: hypoplastic cerebellar vermis with a large cystic fourth ventricle filling an enlarged posterior fossa; presents in infancy with a big head and delay; usually needs a shunt.
- Congenital infections (toxoplasmosis, CMV) and intraventricular haemorrhage of prematurity.
Clinical features
Infants and young children (sutures open)
- Head circumference rising faster than normal (crossing centile lines): measure and plot every visit.
- Tense, bulging anterior fontanelle; separated sutures; thin scalp with distended scalp veins.
- "Sunset" eyes: downward deviation and loss of upgaze from pressure on the dorsal midbrain (Parinaud's).
- Irritability, vomiting, poor feeding, drowsiness, developmental delay; spastic legs in long-standing cases.
- A "cracked pot" percussion note over the skull (Macewen's sign).
Older children and adults (sutures closed)
- Features of raised ICP: morning headache, vomiting, visual blurring, papilloedema, sixth nerve palsy, falling conscious level.
- Acute obstructive hydrocephalus can progress very fast to coma and death ("hydrocephalic attack").
Investigations
- Cranial ultrasound through the open fontanelle in infants (bedside, no radiation).
- CT is the first-line test in older children and adults: size of all ventricles, periventricular lucency (CSF seeping into white matter in acute cases), cause of the block.
- MRI: best for aqueduct anatomy, tumours, Chiari and Dandy-Walker malformations, and for planning endoscopic surgery.
- Lumbar puncture:
- Dangerous in obstructive hydrocephalus or a posterior fossa mass (risk of coning).
- In communicating hydrocephalus it is diagnostic (opening pressure, CSF analysis) and can be therapeutic: removing roughly 10–30 mL to halve the opening pressure gives temporary relief.
Treatment
Acute obstructive hydrocephalus is a neurosurgical emergency.
1. Treat the cause where possible
Removing a posterior fossa tumour or colloid cyst may reopen the CSF pathway. Treat meningitis. Steroids for tumour oedema.
2. Temporary CSF diversion
- External ventricular drain (EVD): catheter usually inserted on the right, just in front of the coronal suture, with its tip in the lateral ventricle near the foramen of Monro. It drains into a bag set at a chosen pressure level, measures ICP and allows CSF sampling and intrathecal antibiotics. Risks: infection, haemorrhage, overdrainage.
- Lumbar drain: for communicating hydrocephalus and CSF leaks only.
- Serial lumbar punctures or ventricular taps: in preterm babies with post-haemorrhagic hydrocephalus.
3. Long-term CSF diversion
| Option | What it does | Notes |
|---|---|---|
| Ventriculoperitoneal (VP) shunt | Ventricular catheter (frontal or occipital horn) → valve and reservoir → tubing tunnelled under the skin → peritoneal cavity | The mainstay; works for obstructive and communicating types |
| Ventriculoatrial / ventriculopleural shunt | Distal end into the right atrium or pleura | When the abdomen is unsuitable (adhesions, peritonitis) |
| Lumboperitoneal shunt | Lumbar theca → peritoneum | Communicating hydrocephalus and IIH only |
| Endoscopic third ventriculostomy (ETV) | Endoscope through the frontal horn and foramen of Monro; a hole made in the floor of the third ventricle (between the mammillary bodies and the pituitary/infundibular recess), letting CSF bypass the block into the basal cisterns | Best for obstructive hydrocephalus from aqueduct stenosis or a tectal tumour; no implanted hardware, so no shunt infection; the opening can close again |
Shunt valves open at high, medium or low pressure. Programmable valves are adjusted with a magnet through the skin. An anti-siphon device stops excess drainage on standing. The reservoir lets CSF be sampled with a needle.
ETV does not work well in communicating hydrocephalus (the absorption problem is beyond the third ventricle). Rare but serious ETV risks are injury to the basilar artery and to the fornix (memory loss).
Shunt complications
| Complication | Features | Management |
|---|---|---|
| Blockage (obstruction) | Commonest problem; debris, protein, choroid plexus, clot, valve failure. Returns of raised ICP symptoms: headache, vomiting, drowsiness, bulging fontanelle; ventricles enlarge on CT | Urgent shunt revision |
| Infection | Usually skin organisms, especially coagulase-negative staphylococci (Staph. epidermidis) forming biofilm on the tubing; most appear within 1 month of insertion; fever, wound redness, abdominal pain, shunt failure | Remove the shunt, temporary EVD (or serial taps), IV antibiotics; new shunt at a fresh site once CSF is sterile and protein normal |
| Overdrainage | Low-pressure headache worse on standing; collapse of ventricles can tear veins → subdural hygroma or haematoma | Higher pressure valve, anti-siphon device, programmable valve |
| Slit ventricle syndrome | Children with long-term shunts and small stiff ventricles; ordinary coughing causes raised-pressure symptoms; a blocked shunt may not show bigger ventricles on CT | Specialist assessment |
| Disconnection or fracture | Tubing breaks, often as the child grows | Revision |
| Abdominal | Pseudocyst, bowel perforation, tubing migration | Surgical |
Shunts are fragile: about 15–20% need replacing within 3 years. Risk factors for infection include very young age, open myelomeningocele, long operations and traffic of staff through theatre.
Shunt problems: "B-I-O-D": Blockage, Infection, Overdrainage, Disconnection.
Normal pressure hydrocephalus (NPH)
- Elderly patients; may follow SAH, meningitis, head injury or tumour, or arise on its own.
- Triad: gait disturbance (broad-based, "magnetic" shuffling; usually first), urinary incontinence, cognitive decline.
- CT/MRI: big ventricles out of proportion to the sulci.
- LP opening pressure is normal (intermittent rises are suspected).
- Tap test or lumbar infusion test predicts who will benefit; treatment is a shunt.
- Important because it is one of the few reversible causes of dementia.
NPH is "wet, wobbly and wacky": incontinence, gait, dementia.
Idiopathic intracranial hypertension (IIH)
- Old names: benign intracranial hypertension, pseudotumour cerebri. "Benign" is misleading because it can blind the patient.
- Typical patient: young, overweight woman; links with some drugs (oral contraceptive pill, tetracyclines, vitamin A derivatives) and raised venous pressure.
- Features: raised-pressure headache, transient visual obscurations, papilloedema, sometimes a sixth nerve palsy.
- Imaging: normal (ventricles small or normal; exclude venous sinus thrombosis with venography).
- LP: raised opening pressure, normal CSF contents. Diagnosis of exclusion.
- Treatment: weight loss, stop offending drugs, acetazolamide (cuts CSF production). If vision is failing: lumboperitoneal or VP shunt, or optic nerve sheath fenestration. Monitor visual fields.
In IIH the ventricles are not enlarged, unlike hydrocephalus. Raised pressure with normal scan = think IIH (after excluding sinus thrombosis).
Expect: obstructive versus communicating hydrocephalus with examples, aqueduct stenosis as the commonest congenital cause (big lateral and third ventricles, normal fourth), colloid cyst blocking the foramina of Monro, infant signs (head circumference, fontanelle, sunset eyes), LP being dangerous in obstructive hydrocephalus, EVD for emergencies, VP shunt as the mainstay and its complications (blockage commonest, infection with Staph. epidermidis within a month, overdrainage with subdural collections), ETV for aqueduct stenosis, the NPH triad, and IIH in young obese women with papilloedema and a normal scan.
Quick revision
- Hydrocephalus = excess CSF + ventricular dilatation.
- Obstructive: aqueduct stenosis, tumours, colloid cyst; LP contraindicated.
- Communicating: post-meningitis (TB), post-SAH/IVH; LP can help.
- Overproduction: choroid plexus papilloma.
- Infant: growing head, tense fontanelle, wide sutures, sunset eyes.
- Emergency: EVD; long term: VP shunt or ETV.
- Shunt failure: 15–20% in 3 years; infection mostly in the first month; remove the shunt to cure it.
- NPH: gait, incontinence, dementia; normal pressure; shunt.
- IIH: obese young woman, papilloedema, normal scan; acetazolamide, shunt or optic nerve sheath fenestration.
Written by The House Job from standard surgical references (Bailey & Love; Kumar and Clark's Clinical Medicine).
FAQ
What is the most common cause of congenital hydrocephalus?
Aqueduct stenosis, which blocks CSF between the third and fourth ventricles, so the lateral and third ventricles dilate while the fourth stays normal.
Why is lumbar puncture risky in obstructive hydrocephalus?
Removing fluid below a block creates a pressure gradient that can drag the cerebellar tonsils down through the foramen magnum.
How is a shunt infection treated?
The whole shunt is removed, CSF is drained temporarily with an external drain, IV antibiotics are given, and a new shunt is placed at another site once the CSF is clear.
When is endoscopic third ventriculostomy preferred to a shunt?
In obstructive hydrocephalus from aqueduct stenosis or a tectal lesion, because it avoids implanted tubing and its infection and blockage risks.
Why does normal pressure hydrocephalus matter?
It is a treatable cause of dementia, and a shunt can improve the gait, continence and memory.