Complications of Shunt Systems

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    A shunt allows individuals to lead full lives, but like any other long-term medically implanted device, it can fail. A shunt is said to have failed when any complication of the treatment of hydrocephalus requires surgery.

    Symptoms of a shunt malfunction may be obvious, redness over the shunt, headache, sleepiness, vomiting, or visual changes. Symptoms may also be subtle, change in behavior, change in school performance. Typically, shunt malfunction is suspected when one or more of the symptoms of hydrocephalus observed prior to shunting return. When complications do occur, further testing is required and you may need to undergo a shunt revision, which is an operation to replace the section of the shunt that is no longer working. When shunt malfunction is suspected, it is critical to seek medical assistance immediately. If you are the parent of a child with hydrocephalus, always remember you know your child best, and if you suspect there may be a problem, trust your intuition, and call the neurosurgeon immediately.

    The most common shunt complications are malfunction and infection.


    Shunt Malfunction or Shunt Failure

    Shunt malfunction also referred to as shunt failure, is a partial or complete blockage (obstruction) of the shunt that causes it to function intermittently or not at all. When a blockage occurs, cerebrospinal fluid (CSF) accumulates and can result in symptoms of untreated hydrocephalus.

    A shunt blockage from blood cells, tissue, or bacteria can occur in any part of the shunt. Both the ventricular catheter (the portion of the tubing placed in the brain) and the distal part of the catheter (the tubing that drains fluid to another part of the body) can become blocked by tissue.

    Shunts are very durable, but their components can become disconnected or fractured as a result of wear or as a child grows. Occasionally they dislodge from where they were originally placed. Breakage causes a total or partial interruption in the shunt pathway, which may obstruct fluid flow and add resistance to the system. A disconnection may occur, but the formation of scar tissue around the subcutaneous catheter may still allow fluid to flow. Migration may also alter shunt function, causing catheters to move to locations that may restrict flow. Rarely, a valve will fail because of a mechanical malfunction.

    If you have a programmable valve and are experiencing symptoms of a shunt malfunction, if it can be determined that your shunt is still capable of flow, your doctor may adjust your setting to avoid an operation.


    Shunt Infection

    Shunt infection is usually caused by a person’s own bacterial organisms and is not acquired from other children or adults who are ill. The most common infection is Staphylococcus Epidermidis, which is normally found on the surface of a person’s skin and in the sweat glands and hair follicles deep within the skin. This type of infection is most likely seen one to three months after surgery but can occur up to six months or more after the placement of a shunt. Patients treated with ventriculoatrial (VA) shunts may develop a more serious infection, which may enter the bloodstream.

    When a shunt infection occurs, the standard treatment is the surgical removal of all of the shunt hardware. An External Ventricular Drain (EVD) is surgically placed to manage the hydrocephalus while the shunt is removed and the infection is being treated. The patient remains in the hospital while the infection is being treated with antibiotics, approximately 10-14 days. When the infection has cleared, the new shunt is implanted surgically.

    NOTE: If you suspect an infection, it’s critical to notify your neurosurgeon immediately or go to the emergency room. Shunt infections can be an emergency and require immediate medical attention to avoid life-threatening complications or possible brain damage.


    Other Shunt Complications

    Over drainage causes the ventricles to decrease in size and may create slit-like ventricles as a result of excessive drainage of CSF. Slit ventricles are most commonly found in young adults who have been shunted since childhood. Some people have slit ventricles but do not experience any symptoms. Symptoms include typical signs of shunt malfunction and often are provoked by standing and relieved by lying horizontal, although if they persist for a long time, they may lose this distinctive characteristic.

    Slit-ventricle syndrome (SVS) may be diagnosed when people have slit ventricles and experience specific symptoms. A particular symptom of SVS is severe intermittent headaches that are often relieved when lying down. Imaging studies are required to determine SVS, which is typically indicated by smaller than normal ventricles. Most shunt manufacturers have shunt hardware designed to help decrease slit-ventricle syndromes.

    Under drainage causes the ventricles to increase in size and can fail to relieve the symptoms of hydrocephalus. To restore a balanced flow of CSF it may be necessary to place a new shunt with a more appropriate pressure setting. For those who have externally adjustable or programmable valves, the balance of flow may be restored by re-setting the opening pressure. Symptoms of under drainage include headaches with increasing frequency and severity, which are often worse on waking in the morning. Also, vomiting and dizziness may be signs of under drainage. In older children, symptoms may include increased irritability, ‘laziness’, poor or disruptive school performance, or even more antisocial activity.

    Adjustment to accommodate patient growth. In children, it may be necessary to modify or revise a shunt in order to adjust for patient growth. For infants implanted at birth, the ventricular catheter may have to be changed around two years to accommodate brain growth. For children, the shunt may need to be revised as the child grows. For instance, as the child gets taller, the tubing from the head to the peritoneal cavity (VP shunt) may need to be replaced with a longer tube. However, neurosurgeons try to minimize the need for revisions. For instance, excess length of VP shunt tubing is placed in the peritoneal cavity with the distal catheter. The catheter slowly pulls out of the peritoneal cavity as the child gets taller. For this reason, regular physician follow-up for shunt assessment and maintenance is crucial, particularly in growing children.

    Subdural hematoma occurs if blood from broken vessels becomes trapped between the brain and skull. This is most common in older adults with normal pressure hydrocephalus (NPH) and requires surgery to correct.

    Multiloculated hydrocephalus is a loculated (isolated) CSF compartment in the brain that is enlarged but not connected to the ventricular system. It may be caused by birth trauma, neonatal intraventricular hemorrhage, ventriculitis (infection of the ventricle), shunt related infection, over drainage or other conditions. This complication may be difficult to identify because it is typically seen in infants and children who may be neurologically compromised. Surgical treatments include placement of multiple shunts, ventricular catheters with multiple perforations or openings, endoscopic or craniotomy to fenestrate (open) the intraventricular loculations.

    Material degradation. Originally, barium sulfate was mixed with silicone to allow shunt catheters to be visible on x-ray. These barium sulfate crystals eventually dissolved, making the tubing surface rough. Tissue in-growth to the roughened surface caused binding of the tubing at specific locations which promoted breakage or deterioration of the tubing. Shunt tubing design has been changed and clear silicone elastomer now covers the surface greatly reducing the possibility of this to occur.

    Seizures sometimes occur in people with hydrocephalus. There is no correlation between the number of shunt revisions or the site of shunt placement and an increased risk of developing seizures. Past studies have shown that children with hydrocephalus who have been treated with a shunt and who also have a significant cognitive delay or motor disability are more likely to experience seizures than those without cognitive or motor delays. Studies have also indicated that seizures are not likely to occur at the time of shunt malfunction and that the most likely explanation of seizure disorder is the presence of associated malformations of the cerebral cortex.

    Abdominal complications in the abdomen can occur in people with hydrocephalus treated with a shunt. Shunt complications that develop in the peritoneum or abdominal area include peritoneal pseudocysts, lost distal catheters, bowel perforations, and hernias. The peritoneum or abdominal area is the most popular site for distal catheter implantation. Although ventriculoperitoneal (VP) shunts do not have fewer complications than ventriculoatrial (VA) shunts, the complications are less severe.

    Infection of a ventriculoatrial (VA) shunt leads to a bloodstream infection and is more concerning than an infection of a ventriculoperitoneal (VP) shunt. Rarely, chronic infection can cause kidney damage or life-threatening damage to the lungs and heart. VA shunts do not fail any more often than VP shunts, but because their complications may be more serious, they are reserved for special circumstances. Complications for Ventriculoatrial (VA) shunts have been associated with pulmonary hypertension, pulmonary tree embolization, and shunt nephritis (an inflammation within the kidney).

    Rare Complications include intestinal volvulus (twisting) around the shunt catheter, formation of encapsulated intra-peritoneal CSF compartments, or development of reactions to the implanted materials.


    Most Common Tests to Assess Possible Shunt Malfunction or Shunt Failure

    It is critical that your doctor diagnoses and treats a shunt complication and shunt infection immediately. Shunt complications are not always straightforward and the diagnosis can be challenging. There are a variety of tests that can help determine if the shunt is working properly. Often, the first step in assessing possible shunt malfunction or shunt failure is imaging. It is important that everyone has a baseline scan on file with your neurosurgeon and hospital. HydroAssist™, HA’s mobile application, allows you to store images.

    Ultrasound (US) is used in infants with open soft spots or fontanels. US has no ill effects on the brain, it is painless, and it requires no sedation. It provides adequate visualization of the lateral ventricles, but other parts of the brain are not so well seen.

    Computed tomography (CT Scan) is a reliable procedure for diagnosing and assisting in the management of hydrocephalus. A CT scan or MRI is used for diagnosis in older children and in adults. In most cases, ventricular size can be compared to prior scans when the shunt was performing well or to “normal values”. When shunt malfunction is suspected, the CT or MRI scan is used to compare the ventricular size and to show the most definitive signs of a malfunction when a prior scan is available for comparison. However, for some people, the ventricles do not enlarge during a shunt malfunction.

    A CT scan It is a sophisticated technique in which x-ray beams are passed through a patient’s body and pictures of the internal structures, in this case, the brain, are made by the computer. CT scans can usually be performed without sedation.

    CT scans do use radiation, raising concerns about exposure, particularly for hydrocephalus patients who rely on CT scans and MRIs multiple times over their lives as critical tools to determine if there is a problem with a current treatment. New machines as well as new techniques that reduce the number of images captured to only the most critically needed to assess a situation, limit the amount of radiation exposure to a patient. You may hear terms like low dose and/or rapid acquisition CT scans. In general, it is better to limit the amount of radiation to which you are exposed. However, this should not come at the expense of your safety. Know the CT techniques used at your hospital, particularly the emergency room. If a CT scan is ordered, it is fine to speak to your doctor about the urgency of the situation and whether or not waiting for an MRI is possible.

    Magnetic Resonance Imaging (MRI), like the CT scan, is a diagnostic technique that produces images of the brain—but unlike CT scanning, MRI does not use x-rays/radiation. Instead, MRI uses radio signals and a very powerful magnet to scan the patient’s body, and the signals are then formed into pictures by a computer. MRI is a painless procedure and has no known side effects. There are two types of MRI scans: The Single Shot Fast Spin Echo (also called a ‘quick brain MRI), which takes about three minutes and rarely requires sedation, is used to assess ventricular size. The full MRI, which takes 30 to 60 minutes and may require sedation, shows more minute details. Before the longer scans are performed, small children are given a sedative to minimize movement that would cause blurring of the images.

    The radiologist will review the scans, write a report, and send the report on to the doctor.

    (It must be noted, that prior to getting an MRI, the clinician must assure that implanted devices are MRI safe.)

    X-ray of the shunt system often called a shunt series is a set of plain radiographs of the entire course of the shunt tubing (skull, neck, chest, and abdomen) to look for mechanical breaks, kinks, or disconnections in the shunt. An X-ray can also confirm the setting on a programmable valve. While a shunt X-Ray can tell the settings of the shunt (if programmable) and if there is a physical break in the catheters, it cannot tell if CSF is actually flowing through the shunt system.

    Despite its enormous importance in the evaluation of suspected shunt failure, brain imaging is not conclusive in every instance. Further investigation generally requires procedures performed by the surgeon or the surgeon’s team.

    Shunt flow studies, which also may be referred to as a shunt patency study or shuntogram, is a study to determine in real-time if CSF is flowing through the shunt system. By injecting a small volume of contrast dye or a radiotracer into the shunt reservoir, the flow of CSF through the catheters and valve can be measured.

    Shunt Tap is a diagnostic test to screen for infection and confirm that the shunt is still functioning. The area of skin overlying the shunt reservoir is cleansed with a sterile antibacterial solution. For a shunt tap, a small needle is used to pierce the skin and access the shunt reservoir/antechamber. The doctor often collects and sends a CSF sample for investigation to rule out any source of shunt-related infection.

    External Ventricular Drain (EVD) is a treatment that allows the temporary drainage of CSF from the lateral ventricles of the brain, or lumbar space of the spine, into an external collection bag. An EVD drains the CSF by using a combination of gravity and intercerbral pressure. The drainage rate depends on the height at which the EVD system is placed relative to the patient’s anatomy relieving raised intracranial pressure (ICP).

    EVDs are often used to relieve elevated ICP, drain infected CSF, drain bloody CSF or blood after surgery or hemorrhage, and monitor the flow rate of CSF.

    Intracranial Pressure Monitoring (ICP) is a diagnostic test that helps your doctors determine if high or low CSF pressure is causing your symptoms. When the cause of a headache has resisted every other diagnostic measure, the surgeon may recommend admission to the hospital for ICP monitoring. ICP monitoring requires a surgical procedure. Your surgeon will make a small hole, called a burrhole, in the skull and a small pressure monitor is inserted through the brain and into a lateral ventricle to measure the ICP. Your pressures are recorded continuously and provide critical guidance for therapy.


    Signs and Symptoms of a Complication

    When things are going well, it’s easy to put the concerns about hydrocephalus and the complications that come with it out of your mind. However, it’s critical to understand the signs and symptoms of shunt failure. Seeing your physician or visiting the Emergency Department, even if symptoms are not ultimately related to hydrocephalus or the shunt, is the right choice. Seeking immediate medical attention can identify a resolvable complication and enable you or your family member to avoid brain damage or even death, especially in children.

    Symptoms of a shunt malfunction or shunt failure considerably from person to person, but recurring failures tend to have similar symptoms for a particular person. When an abrupt malfunction occurs, symptoms can develop very rapidly potentially leading to coma and possibly death. In infants and toddlers, it’s important to be aware that medication with a side effect of drowsiness can mimic or mask signs of shunt malfunction and should be used with caution in those with hydrocephalus, especially infants and young children.

    Infants

    • Enlargement of baby’s head
    • Fontanel full and tense when an infant is upright and quiet
    • Prominent scalp veins
    • Swelling along the shunt tract
    • Vomiting
    • Sleepiness
    • Irritability
    • Downward deviation of eyes
    • Less interest in feeding
    • Fever, potentially present with shunt failure or infection
    • Redness along the shunt tract, potentially present with shunt failure or infection

    Toddlers

    • Enlargement of head
    • Swelling along the shunt tract
    • Vomiting
    • Headache
    • Sleepiness
    • Irritability
    • Loss of previous abilities (sensory or motor function)
    • Fever, potentially present with shunt failure or infection
    • Redness along the shunt tract, potentially present with shunt failure or infection

    Children and Adults

    • Vomiting
    • Headache
    • Vision problems
    • Irritability and/or tiredness
    • Swelling along the shunt tract
    • Personality change
    • Loss of coordination of balance
    • Difficulty waking up or staying awake (this symptom requires urgent attention as it can potentially lead to a coma)
    • A decline in academic or job performance
    • Fever, potentially present with shunt failure or infection
    • Redness along the shunt tract, potentially present with shunt failure or infection

    Older Adults with Normal Pressure Hydrocephalus

    People who are diagnosed and treated in adulthood, including those with NPH, tend to revert to the symptoms they experienced before initial treatment when they are experiencing a malfunction.

    • Difficulty walking/Gait disturbances
    • Cognitive challenges/Mild dementia
    • Urinary Urgency or incontinence
    • Fever (a sign of shunt failure or infection)
    • Redness along the shunt tract (a sign of shunt failure or infection)

    Information you can trust! This article was produced by the Hydrocephalus Association, copyright 2021. We would like to thank Marion L. (Jack) Walker, MD for his valuable contribution and expert input.