CSF shunt (VP shunt)

A tube draining CSF from the brain's ventricles (usually to the abdomen) for hydrocephalus. The one that kills: a blocked shunt raising intracranial pressure - headache, vomiting, drowsiness - which can progress to coning and death.

Adult & paediatricNeurologicalStated practice - no UK guideline found

Also called: VP shunt, ventriculoperitoneal shunt, CSF shunt, cerebrospinal fluid shunt, ventriculoatrial shunt, VA shunt, LP shunt, hydrocephalus shunt, programmable shunt, shunt

What it is

A CSF shunt treats hydrocephalus by draining cerebrospinal fluid from the brain's ventricles, through a one-way valve, to somewhere it can be absorbed - most often the peritoneum (a ventriculoperitoneal / VP shunt), sometimes the heart (ventriculoatrial) or pleura. The valve sits under the scalp, usually behind the ear, with tubing tunnelled down the neck and chest.

The reason this is a neuro emergency and not a plumbing issue: if the shunt blocks, CSF builds up, intracranial pressure rises, and the patient deteriorates - sometimes fast. The review this entry draws on is blunt: Failure to recognize and act on symptoms and signs of shunt malfunction may lead to loss of life or to permanent neurological dysfunction, and because most emergency departments and acute medical units in the UK do not have access to onsite neurosurgical expertise, the ED has to recognise it and escalate. Shunts are common in children (congenital hydrocephalus) and adults (post-haemorrhage, tumour, normal-pressure hydrocephalus).

How to recognise it

A palpable valve/reservoir under the scalp (often behind the ear) with tubing tunnelled down the neck; a scar over the skull and abdomen.
Malfunction presents as raised intracranial pressure. The paediatric pathway lists headache, vomiting, blurred vision, drowsiness and loss of consciousness (which may be episodic), with decreased GCS, papilloedema, loss of upward gaze and - in infants - a bulging fontanelle.
A patient or family who say the shunt 'is blocked again', or who recognise this as their/their child's previous shunt-failure pattern - take them seriously.
Fever points to shunt infection (Fever can be a sign of shunt infection), usually in the months after surgery.

What it gets confused with

A shunt is fully internal (valve under the scalp, tubing under the skin) and permanent; an external ventricular drain has a tube leaving the head to an external collection chamber at the bedside and is temporary. If there is an external CSF collection bag, it is an EVD, not a shunt.

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What goes wrong

Shunt blockage / malfunction (raised ICP)

Headache, vomiting and drowsiness are the classic triad. The review: The coexistence of headache, vomiting and drowsiness make it very likely that an affected patient has shunt dysfunction, and Drowsiness is by far the best predictor of shunt block, while headache and vomiting are less predictive of shunt block.

Red flag
Rising ICP can progress to respiratory arrest, seizure and coning: Shunt blockage may cause blindness and death in the presence of sudden onset and delay in treatment. A normal or unchanged CT does not exclude malfunction. Escalate to neurosurgery urgently; a moribund patient with a reservoir may need emergency CSF tapping by someone competent.

Shunt infection

Fever, often low-grade and intermittent, with headache, drowsiness, malaise, and sometimes redness/tenderness along the shunt track or peritonitis (VP) - usually within months of surgery.

Red flag
Shunt infection (ventriculitis) is devastating and needs neurosurgery, CSF sampling and antibiotics - typically shunt removal plus a temporary external drain. Take blood cultures and start antibiotics per local policy; do not simply treat as a non-specific febrile illness.

Over-drainage

Postural (low-pressure) headache - the review notes postural headaches while sitting up, which resolve when lying down - sometimes with a subdural collection, especially with older or non-programmable valves.

Red flag
Over-drainage can cause subdural haematoma; a shunt patient with a head injury or new focal signs needs imaging. A programmable valve may need its setting adjusted by neurosurgery.

Inadvertent valve reprogramming (programmable valves)

A patient with a programmable valve who has been near a strong magnet or had an MRI, now with new symptoms of over- or under-drainage.

Red flag
An external magnetic field can change a programmable valve's setting. After any MRI the valve must be checked and reset by neurosurgery (see the MRI/diathermy panel).

The first ten minutes

Assess for raised ICP and protect the airway. A drowsy shunt patient can lose their airway and can cone - manage ABC first and get senior/anaesthetic help if GCS is dropping.
Suspect shunt malfunction in any shunt patient with headache, vomiting or drowsiness and no better explanation - in a child especially, One should always suspect shunt malfunction in a symptomatic child with a shunt and no alternative convincing explanation for the symptoms.
Listen to the family. The evidence: families were at least as accurate as paediatricians in diagnosing shunt block.
Investigate and escalate early - FBC, U&E, CRP, blood cultures and a CT brain (comparing with old scans), and discuss directly with neurosurgery; the paediatric pathway: Known neurosurgery patients with potentially blocked shunts presenting to Emergency Departments or General Practitioners should be discussed directly with the on call paediatric neurosurgical registrar (for an adult, the on-call neurosurgical team).
Do not perform a lumbar puncture to 'check' a shunt - Lumbar puncture is usually not recommended, and may be hazardous in obstructive hydrocephalus with non-functional shunts.
Call neurosurgery for any suspected blockage, infection or over-drainage - the definitive assessment and any shunt tap or revision are theirs.

Do not

Do not reassure and discharge a shunt patient with headache, vomiting or drowsiness because the CT looks unchanged.

An increase in hydrocephalus is not always visible, and CT can look normal with a genuine blockage. Clinical deterioration and the family's concern outweigh a reassuring scan; discuss with neurosurgery.

Do not do a lumbar puncture to investigate possible shunt malfunction.

In obstructive hydrocephalus with a non-functioning shunt, LP can be hazardous and precipitate herniation. CSF is sampled via the shunt/reservoir by neurosurgery, not by LP.

Do not dismiss fever in a shunt patient as a simple viral illness.

Shunt infection presents with non-specific fever and malaise and is devastating if missed. Take cultures, start antibiotics per policy, and involve neurosurgery.

Do not ignore a programmable valve after an MRI or magnet exposure.

The valve setting can be changed by an external magnetic field, causing over- or under-drainage. It must be checked and reset by neurosurgery.

Who owns it

Neurosurgery owns the shunt (and the paediatric neurosurgical team in children). Tell them the reason for the shunt, the valve type (programmable or not) and last revision, the current GCS and ICP signs, the CT findings versus old scans, and whether you suspect blockage, infection or over-drainage.

MRI and diathermy with an implanted neuro device

Three implanted neuro devices turn two routine hospital exposures - diathermy and MRI - into potentially lethal ones. The rule is the same for all of them: identify the device from the patient's card, and clear MRI and diathermy with the implanting centre before either happens. Never assume a scan or an operation is safe because the patient 'has had one before'.

Diathermy can kill - deep brain stimulation above all: The device label bars shortwave, microwave and therapeutic-ultrasound diathermy - anywhere on the body, with the system on or off. For DBS the manufacturer is explicit: Energy from diathermy can be transferred through the implanted system and can cause tissue damage at the location of the implanted electrodes, resulting in severe injury or death. Theatre electrosurgery (surgical monopolar diathermy) carries the same risk and must also be flagged - to every surgeon, anaesthetist and physiotherapist.
MRI is conditional, never assumed: MRI is not a simple yes/no - it depends on the device model, the coil and the scan. For DBS a contraindicated scan is lethal: Tissue lesions from component heating, especially at the lead electrodes, resulting in serious and permanent injury including coma, paralysis, or death, can occur if a contraindicated MRI scan is performed. For a cochlear implant, MRI can damage your implant so is best avoided if an alternative scan is possible. Clear every scan with the implanting centre first.
Cochlear implant: diathermy and other energy: Monopolar diathermy can be used below the neck as long as care is taken to ensure that current does not pass near the head: it is safer to use bipolar diathermy where possible. And Procedures such as transcranial magnetic stimulation (TMS), electro-convulsive therapy (ECT) and neurostimulation, should not be undertaken.
Programmable shunt valves and stray magnets: Many CSF shunt valves are programmable - the closing pressure to be altered externally using a special magnetic device - so a stray magnet can change the setting, and it can lead to problems following an inadvertent change of pressure. MRI is a recognised cause of inadvertent reprogramming (per the valve manufacturers' labelling), so after any MRI a programmable valve must be checked and reset by neurosurgery.
What to do: Get the device identification card and the model; flag the implant to everyone planning diathermy, MRI, TMS or ECT; and contact the implanting centre before proceeding. When in doubt, choose an alternative to MRI (e.g. CT) and avoid diathermy entirely.

Who to call

The team and the criteria are national. The phone number is local, and this tool does not know it. Find it once, now, and write it on the department's own card — that is the part no website can do for you.

Say the device name first: Open with laryngectomy, LVAD, shunt — the single word changes who comes and what they bring. Do not bury it in the history.
Say what you have already established: Whether the device is patent, whether it has been removed or disturbed, and what you have already tried. The specialist is deciding whether to walk or run.
Ask who owns it out of hours: Device ownership and the on-call route often differ from the implanting specialty, and it is frequently a regional centre rather than your own hospital.
The patient's own team is a resource, not an afterthought: Named nurse specialists, home-care companies and device helplines answer questions nobody else can, and the patient usually has the number.

When the device is not the problem

A patient with a device gets pneumonia, sepsis, pulmonary oedema and myocardial infarction at the same rate as everybody else. The device is the most visible thing about them and it attracts the whole assessment.

The NTSP says it out loud: The project's own manual warns that patients with tracheostomies can become unwell with all the problems that other patients get too. It is easy to become fixated with the tracheostomy. The same sentence applies to every device in this tool.
Clear the device, then leave it: Establish that the device is doing its job — the stoma is patent, the line draws back, the pump is running — and then assess the patient as you would anyone else.
The anchoring runs both ways: The opposite error is treating a device complication as a medical illness: a blocked gastrostomy read as vomiting, a baclofen pump failure read as sepsis.

NTSP manual — Red flags · read in full

What the patient will be carrying

Shunt patients and families usually carry a shunt card with the valve type and setting and the neurosurgical contact, often keep copies of previous scans, and are frequently expert in recognising that patient's own shunt-failure pattern.

Scope of this page

This page covers recognising and escalating CSF shunt problems in the ED: blockage with raised ICP, infection, over-drainage, and programmable-valve reprogramming. It does not teach shunt tapping, valve reprogramming or shunt revision (neurosurgical procedures), and the detailed algorithm varies with local neurosurgical referral pathways. Shunts are common in adults and children; paediatric care is directed by the paediatric neurosurgical team.