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  • Updated 01.15.2024
  • Released 08.16.1999
  • Expires For CME 01.15.2027

Neurosurgical shunts and their complications



Hydrocephalus remains a complex clinical entity with treatments ranging from endoscopic third ventriculostomy, shunting (ventricular or lumbar), elimination of the obstruction (such as in the case of mass lesion), or choroid plexectomy (rarely performed alone). When placement of a ventricular shunt is indicated, the distal end of the shunt catheter is most commonly placed in the peritoneum; however, over 36 distal shunt diversion sites have been described in the literature (28). Other common distal catheter placement options thus include the atrium of the heart, pleural space, and gallbladder. Although this is an effective treatment, numerous complications can occur in the operative placement and management of neurosurgical shunts. The latest thoughts on the placement and management of shunts are highlighted in this overview. Additionally, the importance of minimizing radiation exposure in evaluating shunted patients is discussed, including the use of rapid sequence MRI scans for surveillance and emergent evaluation. The potential impact of tablet computers on programmable shunts is also reviewed.

Key points

• Shunt malfunction is a life-threatening condition and must be treated urgently or emergently.

• When evaluating for a potential shunt malfunction, it is imperative that the “baseline” image is known to have been taken at a time of shunt function to avoid the misinterpretation of “no change” as the incorrect conclusion of “no evidence of shunt malfunction.” However, one must also use caution as not all patients demonstrate clear ventriculomegaly in the setting of shunt malfunction.

• Image gently in shunted patients as a lifetime exposure to unnecessary radiation puts them at increased risk of developing leukemia, brain tumors, and other cancers.

• Attention to detail in the operating room (reduced traffic, preoperative antibiotics, patient preparation, and efficient operating) is key to reducing shunt infections.

Historical note and terminology

Hydrocephalus, or excessive cerebrospinal fluid, is one of the most commonly encountered neurosurgical conditions.

Shunt malfunction (CT)

Axial images taken at two different levels on a given patient with dysmorphic brain and ventricles (A, B) demonstrate a right parietal ventricular catheter coursing anteriorly and crossing the midline into the left lateral vent...

The first implantable shunt was placed in 1952 by Nulsen and Spitz, and since then, shunt placement has remained the most common treatment of hydrocephalus, despite endoscopic third ventriculostomies with or without choroid plexectomy having made a resurgence in patients (especially in the pediatric population) with obstructive hydrocephalus. (It should be noted that endoscopic third ventriculostomy is typically contraindicated in communicating hydrocephalus.) The peritoneum is the most common location for placement of the distal shunt catheter; however, the distal end is also commonly placed in the right atrium, pleural cavity, or gallbladder. As shunt malfunction can be a life-threatening condition, it is essential to recognize the often progressive and symptomatic signs of shunt failure. This article concentrates on the nature of shunt malfunction, its diagnosis, and management.

Shunt malfunctions. Shunt failures can occur due to obstruction, disconnection, migration, fracture, ascites, abdominal pseudocyst, infections, and even constipation (27). Occlusion of the ventricular catheter is the most common type of mechanical obstruction of shunts and accounts for approximately half of the mechanical obstructions (19). This is typically thought to occur as a result of the choroid plexus growing into the ventricular catheter, although more recent histopathological evidence suggests different types of cellular infiltrates can also cause obstruction, including inflammatory or reactive cells in either early or late shunt failure, respectively (38). It is important to note that the shunt system can occlude anywhere along its course, including the distal catheter, reservoirs, valve, and distal tubing.

Shunt malfunction (rsMRI)
These rapid-sequence MRI (rsMRI) images show evidence of shunt malfunction in this patient with bilateral shunts. (A) demonstrates decompressed ventricles, and (B) demonstrates a dilated left ventricular system. (Contributed by Dr...

Distal obstruction is far less common than proximal obstruction, and the occurrence is more likely to be delayed (14). When distal obstruction is suspected, an abdominal ultrasound study can be useful to look for a pseudocyst, ascites, or constipation. Treatment of infected pseudocysts involves the administration of antibiotics and externalization of the shunt for a brief period. Infection must be ruled out in cases of ascites as CSF ascites can be due to infection, shunt-disseminated metastases, or poor absorption of CSF into the peritoneum (11). Distal obstruction can also occur without an associated infection. In particular, premature infants with a high protein count in their CSF may present with a distal obstruction without associated infection that can often be cleared by irrigating the shunt, obviating the need for an operation.

Disconnection of a shunt rarely occurs early after placement of a new shunt unless there is a technical error. In some shunt systems, the ventricular catheter snaps onto a reservoir, and if this is not done properly, the ventricular catheter can disconnect from the reservoir, resulting in malfunction.

Shunt disconnection
Cranial disconnection between the reservoir and the ventricular catheter on plain radiograph. (Contributed by Dr. Sarah Gaskill.)

Additionally, the catheter is typically tied with a suture to the valve, but if this is not done, there is a higher risk of disconnection occurring. Late fractures often result from chronic mechanical stress associated with patient growth and movement. Using spectroscopy, conventional histology, and scanning electron microscope, Yamamoto and colleagues found that mineral deposits in degraded shunt tubing consisted of hydroxyapatite (45). The most extensive calcification was seen in the neck, presumably due to the increased mechanical stress in this region. The deposition of sodium chloride and other crystals involving the valve has also been demonstrated as a contributing factor in shunt malfunction (40).

Disrupted shunt with calcification in the neck
(Contributed by Dr. Sarah Gaskill.)

Fractured shunt tubing is typically assessed with a shunt series or x-rays of the head, neck, chest, and abdomen in the anterior-posterior and lateral views. However, fractured catheters can be deceiving on x-ray given the fibrous and calcified tracts that can develop. Thus, if there is clinical concern for shunt malfunction, one must consider surgical exploration. Most surgeons will revise a shunt when a fracture or disconnection is demonstrated because the fibrous tract along a fractured shunt can continue to drain CSF for an indeterminate length of time but will ultimately fail.

The evaluation of a shunt malfunction is, first and foremost, a complete history and physical examination, including a funduscopic examination. Symptomatic complaints of shunt calcification may include pain in the neck or chest wall region, limitation of neck movement due to tethering of the shunt, and cutaneous manifestations such as skin irritation overlying the shunt (37). Unfortunately, children with ventriculoperitoneal shunts are at risk of developing malignancies due to repeated exposure to diagnostic radiation (30). Therefore, the Image Gently campaign has emphasized the importance of reconsidering the need for radiation as well as altering the type of radiation performed, particularly in children (13). Multiple studies support not performing a routine shunt series in every child with a possible shunt malfunction unless clinical evidence suggests a fracture or malposition. One such retrospective longitudinal cohort analysis performed by Antonucci and colleagues, most CT scans obtained in the cohort were not followed by surgical intervention (03). If available, rapid sequence MRI can be used to assess the ventricular size as there is no radiation exposure, and it does not require sedation because it can be performed in less than 1 minute. If rsMRI is not available, consideration of a low-dose CT would be another option for minimizing radiation exposure. In a child with an open fontanelle, ultrasound can also be effective. In any event, careful consideration should be given to ordering diagnostic radiation in these patients. The routine of ordering a shunt series and a CT scan on all cases, often even before notifying the neurosurgeon, must be stopped.

When imaging is employed in the evaluation of shunt malfunction, there may not be a discernable radiographic change in ventricular configuration, particularly if the comparison image is from a previous shunt malfunction. This may then lead to a subsequent misdiagnosis of no current shunt malfunction. Thus, it is imperative that the “baseline” image is known to have been taken at a time of shunt function. However, one must also use caution as not all patients demonstrate clear ventriculomegaly in the setting of shunt malfunction.

As technology advances, new modalities for the evaluation of shunt malfunction become available. One publication describes the use of cerebral regional oxygen saturation monitoring in the assessment of pediatric shunt patients. This technology has most commonly been used for the intraoperative monitoring of children undergoing repair of congenital heart disease. The advantage is that it is a noninvasive, easy-to-apply technology that gives instantaneous readings. The researchers found that in the setting of malfunctioning shunts, there was an asymmetrical hemispheric cerebral regional oxygen saturation, and greater changes in regional oxygen saturation occur for distal versus proximal shunt malfunction (01). Although this methodology requires more investigation, it potentially provides another noninvasive and safe technique for evaluating shunt malfunction.

In shunted adult patients with a diagnosis of normal pressure hydrocephalus, a technique of using noninvasive auditory tests (as currently used for universal neonatal hearing screenings) for the diagnosis of cerebrospinal fluid shunt malfunction was described by Sakka and colleagues (36). Ultrasound-based measurements to characterize the movement of flow through the shunt-valve interface in response to CSF flow is another potential mode of noninvasive testing for shunt malfunction (04).

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