Tests to Diagnose Shunt or ETV Failure

How a Shunt or Endoscopic Third Ventriculostomy (ETV) Failure Is Diagnosed

When a person with hydrocephalus experiences symptoms such as headache, vomiting, changes in alertness, or walking difficulties, doctors must determine whether the shunt or endoscopic third ventriculostomy (ETV) is working properly. Because no single test provides all the answers, neurosurgeons use a combination of symptoms, medical history, and diagnostic tests to confirm whether there is a malfunction.

Clinical Evaluation and Symptom Review

The diagnostic process usually begins with a careful review of symptoms and a physical examination. Your doctor will look for changes in alertness, balance, coordination, or vision and compare them to your normal baseline. This evaluation helps guide which imaging or diagnostic tests should be performed next.

The specific tests ordered may depend on your age, the type of shunt you have—ventriculoperitoneal (VP), ventriculoatrial (VA), ventriculopleural (VPL), or lumboperitoneal (LP)—or whether you have an endoscopic third ventriculostomy (ETV), as well as the symptoms you’re experiencing.

Imaging of the Brain and Body

1. Shunt Series X-Rays: A shunt series is a set of X-rays taken to visualize the shunt system; for shunts that start in the head the pictures will include the head, neck, chest, and abdomen (if the shunt goes to the peritoneum).   The goal is to show the entire shunt, allowing doctors to check for:
   • Breaks or disconnections in the tubing or connections
   • Shunt tubes that have migrated out of position, or have kinks
   • The overall location of the shunt catheter

For those with lumbar-peritoneal (LP) shunts, imaging may be limited to the lower spine and abdomen to evaluate tubing placement and integrity.

2. Ultrasound (US): An ultrasound can look through soft tissues to assess for collections of fluid.In infants, the ultrasound can look through the opening in the skull (fontanelle) and assess the ventricle size.Ultrasound can also be used in the abdomen to look for fluid collections or fluid buildup (pseudocysts) around the distal (lower) shunt tubing.
3. CT or MRI Imaging: Both CT and MRI scans create detailed images of the brain to check the:
   • Size of the ventricles – looking for enlarged ventricles or signs of fluid buildup
   • Proper placement of the shunt catheter
   • Changes in structure that can be signs of a shunt problem.

Doctors often compare the new scans to previous “baseline” images taken when the shunt or ETV was felt to be functioning properly, and thus to detect even small changes.

An MRI may also be used to check CSF flow. There are different MRI sequences that can show the presence or absence of flow.  “Cine studies provide a set of moving images that show the spinal fluid flow; other sequences show ‘flow void’ changes that show fluid movement.

These studies can define the flow or absence of flow through an ETV opening at the bottom of the third ventricle, or fluid flow through the normal small passages in the brain.

Testing Cerebrospinal Fluid (CSF) and Blood

1. Shunt Tap: A shunt tap is a procedure in which a sterile needle is inserted into the shunt’s reservoir to access the inside of the shunt and the spinal fluid. It may be possible to then:
   • Obtain a sample for infection testing
   • Measure CSF pressure
   • Check for CSF flows

Because there is a risk of infection, this test is performed only by trained professionals under controlled (aseptic) conditions.

2. Lumbar Puncture (Spinal Tap): Sometimes, a lumbar puncture is used to measure CSF pressure (accessing the fluid in the lower spine). It helps determine whether pressure is abnormally high or low, which may indicate shunt under-drainage or over-drainage.
3. Blood Tests: Blood work may be ordered to check for signs of infection or inflammation.
   Elevated white blood cells or other markers may suggest a shunt infection or systemic illness.

Tests That Directly Evaluate Fluid Flow or Pressure

1. Shunt Flow Studies (Shuntogram or Shunt Patency Study): The classic shunt flow test is a nuclear medicine test, where a very small amount of radioactive tracer is injected into the shunt reservoir during a shunt tap.Imaging then tracks  as the tracer moves through the system, assessing if the shunt is open and it may assess how quickly and efficiently the fluid is movingThis test helps pinpoint blockages or slow flow within the shunt tubing.Other shunt flow tests may be used to assess flow through the shunt – using temperature changes or special ultrasonic equipment to define flow.
2. Intracranial Pressure (ICP) Monitoring: ICP monitoring directly measures the pressure inside the skull over a period of time.A small sensor or catheter is surgically placed through the skull into the brain or ventricles to record continuous pressure readings.It can define the actual pressure inside the head, and helps to identify under-drainage, over-drainage, or intermittent blockage that may not appear on imaging.
3. External Ventricular Drain (EVD): If imaging and other tests are inconclusive—or if the shunt must be removed due to infection—doctors may place a temporary drainage system called an external ventricular drain (EVD).The EVD allows:

• • Continuous monitoring of CSF flow and pressure
  • Drainage of excess fluid
  • Assessment of whether symptoms improve when CSF is drained

Additional Testing for ETV Patients

For individuals with an endoscopic third ventriculostomy (ETV), testing focuses on confirming that the surgical opening (stoma) is still open and CSF is flowing normally. MR Imaging (either cine flow or other flow determining images) is the primary imaging tool used to visualize this flow. If symptoms return and imaging shows reduced or no flow through the stoma, the ETV may be partially or completely closed.

When to Seek Immediate Medical Care

Seek emergency evaluation if you or your child experiences:

• A sudden or severe headache
• Repeated vomiting
• Unusual sleepiness or irritability
• Redness or swelling along the shunt tract
• Fever or neck stiffness

Prompt testing and medical attention are essential—shunt malfunction or ETV failure can progress quickly and requires urgent care.

What Happens Next

If testing shows a blockage or malfunction, your neurosurgical team will discuss next steps. Treatment may include revising or replacing the shunt, reopening the ETV, or temporarily placing an external drain while the cause is identified. With prompt care, most people recover well after the appropriate intervention.

Diagnosing a shunt or ETV malfunction involves multiple tests that work together to provide a clear picture.

Your healthcare team will combine results from imaging, fluid analysis, and pressure monitoring with your symptoms and medical history to determine the best plan for your care.

Information you can trust! This article was produced by the Hydrocephalus Association, copyright 2025. We would like to thank Bruce A. Kaufman, MD for his valuable contribution and expert input.

This article is designed to provide helpful information on the subjects discussed. It is not intended as a substitute for treatment advice from a medical professional. For diagnosis or treatment of any medical condition, consult your doctor.