Shunt Malfunction (Shunt Failure)

How a shunt works

Hydrocephalus is a build-up of cerebrospinal fluid in the brain's cavities (ventricles). A shunt is a thin silicone tube system that drains this fluid elsewhere in the body, where it is absorbed. It has three parts:

1. Ventricular catheter: in a ventricle of the brain.
2. Valve: under the scalp, behind or above the ear. It controls flow and often has an adjustable (programmable) pressure setting.
3. Distal catheter: runs under the skin to the abdomen (VP shunt), or less often to the heart (VA shunt) or lung lining (VPL shunt).

Shunts are lifesaving, but they are mechanical devices that can fail at any time, from days to decades after placement.

Causes of shunt malfunction

Symptoms of shunt malfunction

Symptoms reflect rising pressure inside the skull. They can build over hours or days, and they tend to be similar each time a person's shunt fails, so families often learn to recognize "their" pattern.

In babies

• a full, tense or bulging fontanelle (soft spot)
• a head that grows faster than expected, with prominent scalp veins
• vomiting, poor feeding and irritability
• sleepiness, or a high-pitched cry
• eyes fixed downward (sunsetting)
• seizures

In children and adults

• headache, often worse on waking or lying down
• vomiting, especially in the morning
• drowsiness or lethargy
• blurred vision, double vision or a new squint
• irritability, personality change, worsening school or work performance
• loss of balance, new weakness, or a return of old symptoms
• in adults with normal pressure hydrocephalus: worsening walking, memory and bladder control

Signs of shunt infection

Fever, redness, tenderness or swelling along the tubing, fluid leaking from the incision, abdominal pain and general malaise can signal infection. Infection can also simply look like a blocked shunt. Meningitis can result.

Overdrainage

Too much drainage causes headaches that come on when upright and ease lying down, nausea and dizziness. Over the long term it can cause slit ventricle syndrome or blood collections over the brain (subdural hematomas).

Diagnosis

A neurosurgical team assesses the person urgently. Steps include:

• History and exam: how symptoms compare with past malfunctions, the eyes (for swelling of the optic nerve), consciousness and the shunt tract.
• Brain imaging: a CT scan or rapid "shunt series" MRI to compare ventricle size with previous scans. Ventricles do not always enlarge, so a normal scan does not rule out a malfunction.
• Shunt series X-rays: images of the head, neck, chest and abdomen to look for breaks, disconnections or migration.
• Abdominal ultrasound: to look for a pseudocyst.
• Shunt tap: a fine needle into the valve reservoir to measure pressure and test fluid for infection.

Some people need monitoring of pressure inside the skull before a decision is made.

Treatment

• Shunt revision: surgery to replace the blocked or broken part, or the whole shunt. Most revisions take 1 to 2 hours.
• Infection: the infected shunt is usually removed, an external drain is placed temporarily, and intravenous antibiotics are given before a new shunt is put in.
• Overdrainage: adjusting a programmable valve, or adding an anti-siphon device.
• Endoscopic third ventriculostomy (ETV): some people can have a small opening made in the floor of the third ventricle so fluid bypasses the blockage, removing the need for a shunt.

Living with a shunt

• Know the type of shunt and valve, and carry a card or medical ID.
• Keep a copy of a recent "baseline" brain scan report for comparison in emergencies.
• After any MRI, a programmable valve may need to be checked and reset, because magnets can change its setting.
• Teachers, caregivers and coaches should know the warning signs.
• Most children with shunts attend regular school and play sports; contact sports are discussed individually with the neurosurgeon.

Frequently asked questions

What are the first signs of a shunt malfunction?

Common early signs are headache, vomiting, sleepiness and irritability. Babies may have a bulging soft spot and feed poorly. Older children and adults may notice vision changes, confusion or worse balance. Symptoms are often similar to previous episodes for the same person.

What does a VP shunt malfunction headache feel like?

It is often worse on waking or when lying down, may ease after sitting up or vomiting, and steadily worsens over hours to days. A headache that is worse when standing and better lying down suggests overdrainage instead.

How long do VP shunts last?

There is no fixed lifespan. Some work for decades, while many need revision within the first 2 years. Over a lifetime, most people with a shunt need at least one revision, often because of blockage or a child outgrowing the tubing.

Can a shunt malfunction be life-threatening?

Yes. A blocked shunt can raise pressure inside the skull quickly, leading to brain damage or death if untreated. That is why sleepiness, vomiting and severe headache in someone with a shunt need emergency assessment, even if earlier scans were normal.