The placement of a ventriculoperitoneal (VP) shunt requires meticulous planning and attention to detail. This chapter provides a review of the technique for placing a VP shunt. This procedure is indicated primarily for the treatment of primary or secondary hydrocephalus in adults and children.
The diagnosis of hydrocephalus is reasonably straightforward in most patients. Patients with acute hydrocephalus experience classic symptoms (headaches, vomiting, and mental status changes) and signs (up-gaze palsy, declining mental status, and bradycardia) of elevated intracranial pressure.
Other patients might have more subtle considerations for cerebrospinal fluid (CSF) diversion. A variety of protocols exist for patients suspected to have normal-pressure hydrocephalus. Patients with idiopathic intracranial hypertension or pseudotumor cerebri can have multiple treatment options. Shunting in children with macrocephaly or subtle loss of developmental milestones might also merit consideration.
There are inherent complications with placing a shunt. In the hands of an experienced surgeon, the immediate surgical risks are generally acceptable, with an approximate 1% chance of clinically relevant intracranial hemorrhage and an approximate 1% chance of damaged abdominal viscera. The risk of shunt infection is approximately 5% to 8%. Approximately 50% of all children who undergo shunt placement will require a shunt revision within 2 years.1,2
Some patients with hydrocephalus benefit from an endoscopic third ventriculostomy, which can often adequately treat obstructive hydrocephalus without all of the potential long-term complications of shunting (see chapter for further details).
Once the decision to place a shunt is finalized, the surgeon must evaluate the patient’s ventricular anatomy. The shunt is placed most commonly on the right side and in the frontal horn of the lateral ventricle via a parieto-occipital entry point, but a different location might be required for patients with abnormal anatomy. Some children with severe hydrocephalus have a very thin or nonexistent cortical mantle. I prefer to place the proximal catheter through some cortex so that it acts as a gasket to prevent leakage of CSF around the catheter. The use of neuronavigation is helpful for placing all catheters, but it can be critical for hitting a smaller target.
After planning the target location of the proximal ventricular catheter, the surgeon then selects an appropriate distal terminus. Multiple anatomic locations are acceptable. The peritoneum is the most common distal site for a number of reasons. Accessing the peritoneum is safe, and the peritoneal cavity generally absorbs CSF quite well. In children, excess catheter can be placed to allow for the patient’s growth.
The right atrium of the heart is also an acceptable distal site. The rates of shunt infection or malfunction between ventriculoatrial (VA) and VP shunts are similar. Because CSF normally is absorbed into the venous system, the atrium is an ideal physiologic location. However, the atrium is generally the second choice because of the risks of thrombosis, endocarditis, myocardial injury, nephritis, and arrhythmias. The distal catheter of the VA shunt is of a fixed length. A growing child might need lengthening of this distal catheter with age (see the Ventriculo-Atrial chapter for further details).
The pleural space is another accepted distal site. However, ventriculopleural (VPl) shunts have a higher failure rate than do VP and VA shunts, so the pleural space is considered a salvage location. A number of disadvantages to VPl shunts exist. The pleura is sensitive, and some patients will have pain associated with the presence of the distal catheter. The lung capacity in infants is very small and might not be able to handle the amount of CSF, and many experienced shunt surgeons will not place a VPl shunt in children younger than 7 years of age for this reason. The pleural space also imparts a negative pressure on the shunt system. With every inspiration, the shunt is subjected to a “suck” that can lead to a low- or even negative-resistance situation. Proper valve selection is critical for avoiding overdrainage and slit-ventricle syndrome.
The gallbladder is an infrequently used distal terminus (see the Ventriculo-Gallbladder chapter) but can be quite effective in selected patients who have not tolerated other distal locations. Other distal sites that have been described include the transverse sinus and bone marrow.
Once the anatomy is defined, the surgeon selects the valve and shunt system. Multiple shunt valves are commercially available. The surgeon who treats hydrocephalus routinely should be familiar with the advantages and disadvantages of multiple valves and can select the optimal system for the patient (see Ventricular Shunt Reference chapter for further information about the valves).
The patient is positioned supine with his or her head turned opposite the side of the proximal catheter. The head should be rotated 45° to 60° away from the surgeon with a slight posterior tilt. More rotation is needed if an occipitoparietal shunt is planned. A bump is placed under the shoulders to provide a straight line between the thorax, neck, and retroauricular region. The mastoid process and the clavicle should be in approximately the same horizontal plane, which facilitates safe tunneling.
The entire length of the shunt path should be exposed and surgically prepared. Enough hair is clipped to enable a clean incision and skip incision(s) if necessary. It is not necessary to shave the patient’s entire head. Preoperative antibiotics are given. The surgical team should all double glove, because this practice has been shown to reduce the risk of shunt infection.
The proximal catheter is placed most commonly in the frontal horn of a lateral ventricle from either a frontal or occipitoparietal approach. Ideally, the catheter rests in front of the foramen of Monro, away from the choroid plexus. The skin incision is curvilinear and should be fashioned such that it is away from the shunt hardware.
The key anatomic landmarks for placing a frontal catheter include the medial canthus of the ipsilateral eye and the tragus of the ipsilateral ear. Kocher’s point, located 1 to 2 cm anterior to the coronal suture and 3 cm lateral from the midline, is used for placement of the burr hole. In infants, the corner of the anterior fontanelle is a good site for entry. A retroauricular skip incision is generally required for frontal shunts.
There are multiple ways to estimate the location of the incision for an occipitoparietal catheter. Frazier’s point is 3 cm lateral from the midline and 6 cm superior to the inion. This point is a common anatomic landmark for placing the burr hole for an occipitoparietal shunt. The prefer the use of image guidance for mapping the location of the incision.
Another simple method for estimating the burr-hole placement for an occipitoparietal shunt is to measure a mark halfway between the external acoustic meatus and the inion. A second measurement is made halfway between this mark and the vertex of the skull. A flatter area of the skull exists just superior and posterior to this mark, which makes an ideal entry point for an occipitoparietal shunt catheter.
A pocket for the valve is created between the periosteum and the galea in the plane of the loose areolar tissue. It is critical to define this plane precisely, because in infants, the galea is the only layer that will hold a deep suture. The galea must be kept attached to the skin. Some valves or antisiphon devices require a specific orientation in space and the surgeon must understand the nuances of each valve.
There are 3 common ways to access the abdomen, via minilaparotomy, laparoscopically, and with the use of a trocar. The trocar method requires a small incision that should be made superior to the umbilicus to avoid bowel perforation. The trocar is inserted through the skin and subcutaneous fat until it rests on the anterior rectus sheath. Then, while pulling the skin taut anteriorly, the trocar is advanced by aiming for the ipsilateral iliac crest. As the trocar is advanced, a “pop” should be felt when it passes through the anterior rectus sheath and again through the posterior rectus sheath. Afterward, the stylet is removed, and the sheath is left in place. The laparoscope-assisted method is especially useful in obese patients and is typically performed by a general surgeon.
Minilaparotomy is the most common method for accessing the peritoneal space. Multiple sites for the incision have been described. Using a lateral subcostal incision confers the advantage of entering the peritoneal space over the liver, thus minimizing the risk of bowel perforation. The surgeon must navigate 3 layers of muscle.
A midline, vertical incision provides the advantage of going through the avascular linea alba. A common insertion site is superior and lateral to the umbilicus; either side is acceptable. The right side is preferred in patients who might need a gastrostomy tube. This is a simple exposure, and the muscle and the fascia act together as a gasket to support the distal tubing and prevent CSF leakage.
A transverse minilaparotomy incision is carried through the fat and Scarpa’s fascia to the anterior rectus sheath. The anterior rectus sheath is opened transversely. The rectus abdominus muscle is visualized, and a hemostat is used to split these fibers vertically, in line with their orientation.
Then, the glistening white posterior rectus sheath is visualized and mobilized with 2 hemostats; the surgeon must take care to pull the sheath toward himself or herself. The surgeon will grab the sheath with 1 hemostat and use a second hemostat to sweep away the muscle. By working back and forth with the 2 hemostats, a section of the posterior sheath can be exposed. When this technique is used, the underlying bowel should fall away from the area.
The posterior rectus sheath is opened with scissors. Most of the time, the peritoneum is opened with this maneuver. A blunt instrument should pass without resistance. If resistance is encountered, the next layer encountered is generally the peritoneum, and preperitoneal fat might be seen. The peritoneum is generally translucent; the surgeon should be able to handle the scissor tips under direct vision through the tissue before cutting, which helps him or her avoid inadvertently cutting the bowel. The undersurface of the abdominal wall is very smooth and the surgeon’s figure can feel this surface to assure himself or herself that the abdominal cavity has been entered.
The distal catheter will be difficult to pass or will curl up if it is within the preperitoneal space. A catheter left in this space will generally fail quickly. Fluoroscopy can be used to ensure that the catheter distributes freely into the appropriate space. A tightly coiled catheter (generally determined via C-arm imaging) is unacceptable. The neurosurgeon should not hesitate to consult a general surgeon regarding any patient who has undergone multiple previous abdominal surgeries, which can lead to adhesion formation. The entire incision is packed with a bacitracin-soaked sponge and the attention is diverted elsewhere.
Next, the subcutaneous tunneling is performed. In some ways, this tunneling is the most immediately dangerous part of the procedure. The shunt passer is generally passed from the head toward the abdomen, although the opposite way is acceptable. The most resistance is encountered in the neck. After the nuchal fascia is penetrated, it is critical for the surgeon to keep the passer above the clavicle to avoid a pneumothorax or lung injury. The tunneling should not occur too close to the skin to minimize the risk of inadvertent skin penetration or future shunt erosion.
To avoid esophageal injury, the midline should not be crossed until the passer is palpated over the clavicle. Also, the shunt passer should not go directly under the breast in a developing girl, because it could injure the breast bud. In infants, tunneling might restrict ventilation. The anesthesia team should be notified before tunneling, and this part of the procedure should be done as efficiently as possible.
After the distal catheter is passed, its end is covered with a sterile towel. Then, the valve is attached. The system is then flushed with fluid that does not contain bacitracin; bacitracin fluid can cause bubbles that can airlock the system and cause an obstruction.
A small cruciate opening of the dura suffices, and the edges of the dura are coagulated with bipolar electrocautery. The pia is coagulated and opened, and the proximal catheter is inserted using navigation. It is important to resist the temptation to pass the frontal catheter too deeply (max of 7cm in adults.) Ideally, the distal system is in place and flushed before placing the proximal catheter. Then, the proximal catheter can be connected to the system quickly to prevent excessive egress of CSF or inadvertent dislocation of the proximal system. Distal flow is confirmed.
The surgeon then “taps” the valve with a 25-gauge butterfly needle; this maneuver confirms proximal flow and enables the injection of intrathecal antibiotics. A standard protocol is to use 10 mg of intrathecal vancomycin and 4 mg of intrathecal gentamycin. This dose is the same regardless of the age or size of the patient. The distal catheter is occluded for this injection to force the antibiotic into the ventricle. Once the distal flow is confirmed, the valve is pulled into the subcutaneous pocket, and the distal catheter is placed into the peritoneal cavity.
The last move in positioning the valve should be a “pull” not a “push”; the valve must be pulled into the pocket from below, not pushed from above. Pushing can cause the segment of the catheter just distal to the valve to kink and occlude.
In infants, the reservoir and proximal catheter can “piston,” because relatively little scalp tissue is there to hold it in place. Such pistoning can contribute to CSF leaks and potential infections. I recommend placing a stitch through the periosteum on either side of the burr hole in an effort to tack the reservoir or valve down.
The incisions are closed, and a sterile dressing is applied. The incision should be irrigated copiously with antibiotic-impregnated solution before closure.
Antibiotics are continued for 24 hours after shunt placement. Surgeons who routinely place shunts are encouraged to adopt a shunt infection-prevention protocol. The protocol from the hydrocephalus research network is cited below.3 Dressings are removed 48 hours after the procedure, and the patient then can shower and wash his or her hair.
Patients are mobilized as quickly as possible. Newborns are positioned with their head elevated above the heart in an effort to prevent CSF pressure on the cranial incision.
The most surgical pain is generally in the neck and results from the shunt passage. Ice packs are beneficial. Many surgeons document the position of the catheter and distal system with a head computed tomography scan without contrast and a “shunt series” of radiographs. Patients without complications are observed overnight and discharged the next day.
Pearls and Pitfalls
- Stereotactic navigation and intraoperative ultrasonography have been used with great success for guiding catheter placement. These tools have led to greater accuracy and lower revision rates.
- Routine use of an endoscope to place a shunt catheter is not indicated and can increase complication rates.
- Puncturing the lung during subcutaneous tunneling is a risk. It is critical to keep the tunneler within the subcutaneous space and palpable throughout the entire tunneling process.
- Each institution is encouraged to adopt a protocol for minimizing the risk of shunt infection.
- A general surgeon should be consulted regarding patients with multiple previous abdominal surgeries or with a previous abdominal shunt infection. These patients are at high risk for adhesions and surgical bowel perforation.
Contributors: Adam Leibold, BS, ScM, Janit Pandya, BS, and Daniel Fulkerson, MD
- Drake J, Kestle JR, Milner R, et al. Randomized trial of cerebrospinal fluid shunt valve design in pediatric hydrocephalus. Neurosurgery 1998;43:294–305; discussion 303–305 (10.1097/00006123-199808000-00068).
- Kestle J, Drake J, Milner R, et al. Long-term follow-up data from the shunt design trial. Pediatr Neurosurg 2000;33:230–236 (10.1159/000055960).
- Kestle J, Holubkov R, Douglas Cochrane D, et al. A new Hydrocephalus Clinical Research Network protocol to reduce cerebrospinal fluid shunt infection. J Neurosurg Pediatr 2016;17:391–396 (10.3171/2015.8.PEDS15253).
Please login to post a comment.