Hydrocephalus

Communicating vs non-communication (obstructive)

Pressure (high, normal, low) cf compliance

Excessive CSF production - only 1 cause (papyloma? patoloma? unclear)

Low compliance (slit ventricle)

Posterior vault expansion → improved condition.

Using pump-valve.

in just 6 months, ETV already failing; shunt takes longer

but overall score on cognitive, etc, there is no meaningful differences.

Shunts have a bad rep - especially with paediatrician because it got blocked, etc.

3 incision: head, neck (for the valve), and abdomen for the CSF to flow.

Valve can fail, but ETV fails quicker than VP-shunt.

ETV acts as a short-term measure to reduce ICP, but VP-shunt can be a long-term solution.

24-hr lying down

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.

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.

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 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.

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.

A shoulder bump was placed to keep the mastoid process and the clavicle on the same plane.

It is not necessary to shave the patient’s entire head.

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.

Kocher’s point is located 1 cm anterior to the coronal suture and 2 to 3 cm lateral to the midline. A catheter placed perpendicular to the brain at this location should enter the ipsilateral lateral ventricle.

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.

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 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.

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.

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.

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.

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.

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.

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 of positioning a shunt should always be a “pull” not a “push," because pushing the valve into the pocket can lead to kinking of the distal catheter.

Antibiotics are continued for 24 hours after shunt placement.

Dressings are removed 48 hours after the procedure, and the patient then can shower and wash his or her hair.

The most surgical pain is generally in the neck and results from the shunt passage. Ice packs are beneficial.

Patients without complications are observed overnight and discharged the next day.

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.