Ventriculoperitoneal (VP) Shunts - Everything You Need to Know

What Is a VP Shunt?

• Ventriculoatrial (VA) - drains to the right atrium
• Ventriculopleural - drains to the pleural space
• Lumboperitoneal (LP) - drains from the lumbar subarachnoid space to the peritoneum (used in normal-pressure hydrocephalus and idiopathic intracranial hypertension)

Indications

• Obstructive (non-communicating) hydrocephalus - e.g., aqueductal stenosis, posterior fossa tumors
• Communicating hydrocephalus - e.g., post-hemorrhagic, post-meningitic, idiopathic
• Normal pressure hydrocephalus (NPH) - classic triad: gait disturbance, dementia, urinary incontinence
• Idiopathic intracranial hypertension (IIH) - when medical therapy fails and vision is threatened
• Posthemorrhagic ventricular dilatation (premature neonates)

Components of the System

• Fixed-pressure valves - open when CSF pressure exceeds a set threshold (low, medium, high resistance)
• Programmable (adjustable) valves - opening pressure changed non-invasively with an external magnetic device; preferred because overdrainage can be corrected without surgery
• Anti-siphon device - prevents excessive drainage when the patient stands upright
• The valve typically incorporates a CSF reservoir dome that can be percutaneously tapped for sampling or pressure measurement

Examples of VP shunt valves - Bailey & Love's Surgery

How It Works

Surgical Technique (overview)

1. A small burr hole is made in the skull (typically right parietal or right frontal)
2. The ventricular catheter is passed into the ipsilateral lateral ventricle
3. The valve/reservoir is secured to the skull
4. The distal catheter is tunnelled subcutaneously (neck → chest → abdomen)
5. The distal tip is placed in the peritoneal cavity via a small abdominal incision

Complications

1. Obstruction (Most Common)

• Most common cause of shunt failure
• Usually at the ventricular catheter tip or at the valve
• Proximal causes: choroid plexus adhesion, blood clot, proteinaceous debris, infection
• Distal causes: omental wrapping, peritonitis, thrombus, catheter migration, pseudocyst formation
• Presentation: features of raised ICP - headache (worse on waking), vomiting, drowsiness, papilledema; in infants - bulging fontanelle, sunsetting eyes, irritability
• Emergency if obstructive/congenital hydrocephalus - rapid deterioration from uncontrolled ICP rise

2. Infection (Most Serious)

• Occurs in 2-10% of cases
• ~70% present within 2 months of placement (colonization at time of surgery is the main mechanism)
• Common organisms: Staphylococcus epidermidis, S. aureus, gram-negative bacilli
• S. epidermidis adheres to shunt surfaces and produces a biofilm (mucoid substance) that protects it from host defenses; the Silastic material also impairs leukocyte adherence
• Presentation: fever, headache, meningism; may be subtle/indolent
• Diagnosis: CSF tap from shunt reservoir (lumbar puncture if safe); note - culture may be negative even in proven infection
• Treatment: Remove shunt + external ventricular drainage (EVD) + antibiotics; reinsert new shunt once CSF clears

3. Overdrainage

• Rapid decompression of enlarged ventricles can tear bridging veins
• Causes: subdural hygroma or subdural haematoma
• Slit ventricle syndrome (SVS): chronic overdrainage in children leads to underdeveloped ventricles/subarachnoid spaces and poor brain compliance; normal ICP fluctuations become exaggerated; symptoms (headache, nausea) are positional - worse upright, better supine; CT shows slit-like ventricles
• Extra-axial fluid collection: estimated in ~3.4% of cases
• Treatment: raise the valve pressure (programmable valve) or add an anti-siphon device

4. Mechanical (Fracture/Migration)

• Catheter fractures or disconnects (common over years due to patient growth in children)
• Presents similarly to obstruction (subtle raised ICP signs)
• Identified on shunt series X-rays

5. Shunt Nephritis (rare)

• Chronic low-grade bacteremia from an infected VA shunt (less relevant for VP, more for VA shunts) causes immune complex deposition in glomeruli
• Treatment: remove shunt + antibiotics; hemodialysis preferred if dialysis needed (peritonitis risk with peritoneal dialysis)

Clinical Assessment of Shunt Function

History & Exam

• Headache pattern (worse on waking/bending/Valsalva)
• Vomiting, visual changes, cognitive decline
• Palpate the shunt along its subcutaneous tract - look for wound breakdown, CSF leak, disconnection

Manual Pumping Test

Imaging

• Non-contrast CT head - first-line; look for enlarged ventricles vs. baseline; sensitivity 83%, negative predictive value 93% for obstruction
  • Always compare to the patient's previous scans (many have abnormal baseline)
  • 9-15% of pediatric patients have poor brain compliance - ventricles won't enlarge even in severe shunt failure
• Shunt series X-rays - AP/lateral skull + AP chest + AP abdomen; detects kinking, fracture, disconnection, migration; sensitivity only 20% but essential when CT is abnormal to localize the failure point
• MRI - useful but can reset programmable valve settings; always consult neurosurgery before MRI in programmable valve patients
• Radionuclide shunt patency study - rarely used but can confirm flow through the system

CT showing persistent hydrocephalus despite shunt - suggests malfunction. - Tintinalli's EM

Shunt Tap

• Performed to: confirm malfunction, rule out infection, or acutely relieve life-threatening ICP
• Should be done by neurosurgery whenever possible
• If neurosurgeon unavailable and the patient is deteriorating, an EM physician should perform it
• Technique: shave + sterile prep over the valve/reservoir; use a 25-gauge butterfly needle; measure opening pressure; send CSF for cell count, glucose, protein, culture

When to Call Neurosurgery

• Suspected shunt obstruction in obstructive/congenital hydrocephalus (risk of rapid herniation)
• Deteriorating consciousness or focal neurology
• CT showing progressive ventriculomegaly vs. baseline
• Symptoms of infection + known shunt

Special Considerations

Key Numbers to Remember