Neuronavigation and Laparoscopy Guided Ventriculoperitoneal Shunt Insertion for the Treatment of Hydrocephalus

Summary

Patient outcomes of ventriculoperitoneal (VP) shunt surgery, the mainstay treatment for hydrocephalus in adults, are poor due to high shunt failure rates. We present intraoperative footage of VP shunt insertion using neuronavigation and laparoscopy guidance, with the goal to reduce the risks of proximal and distal shunt catheter failures, respectively.

Abstract

Hydrocephalus is a common adult neurosurgical condition typically requiring treatment with a cerebrospinal fluid (CSF) shunt, of which the ventriculoperitoneal (VP) shunt is the most common type. Unfortunately, the failure rates of VP shunts are alarmingly high, with up to 50% of patients requiring revision surgery within 2 years. VP shunt failure may occur due to infection, or catheter mispositioning, migration, and occlusion. We undertook a joint neurosurgery and general surgery collaboration in a 7-year prospective non-randomized consecutive quality improvement cohort study to reduce the rates of ventriculoperitoneal (VP) shunt failures in 224 adult patients at a tertiary care institution. The initiative combined the use of electromagnetic stereotactic neuronavigation to guide the placement of the proximal catheter and laparoscopy to place the distal catheter under direct visualization. With laparoscopic assistance, the distal catheter was anchored through a small hole created in the falciform ligament and placed into the right retrohepatic space, free from the omentum, adhesions, or bowel that might obstruct the catheter tip. The surgeries were performed using a shunt infection prevention protocol to reduce the risk of shunt infections. Here, we present an intraoperative video of the surgical procedure. Compliance with shunt infection reduction strategies and the combined utilization of neuronavigation and laparoscopy techniques in adult VP shunt surgery resulted in a 44% reduction in the risk of overall shunt failure. The significant positive impact with regard to shunt-failure-free patient outcomes among patients who underwent VP shunt surgery using this strategy underscores the value associated with the use of these modern intraoperative techniques and cross-specialty collaboration during VP shunt surgery.

Introduction

Hydrocephalus, a common neurological disorder affecting approximately 175 per 100,000 adults worldwide¹ is characterized by the accumulation of cerebrospinal fluid (CSF) within the cerebral ventricles due to an imbalance between CSF production and uptake processes in the brain². As various non-surgical therapies have been unsuccessful³, the only viable treatment of hydrocephalus is the surgical diversion of the CSF from the cerebral ventricles. The most common approach utilized in adults is the placement of a shunt that drains the ventricular CSF into the peritoneal cavity (ventriculoperitoneal [VP] shunt)^4,5.

A VP shunt has three subcutaneously located components: a proximal ventricular catheter inserted into a CSF ventricle through a skull burr hole, a valve to regulate the flow, and a distal catheter to connect the valve to the peritoneal cavity where the CSF is deposited and reabsorbed (Figure 1). Alternatively, a shunt can drain into the venous system at the level of the right atrium (ventriculoatrial [VA] shunt)^6,7 or divert the spinal CSF from the spine into the peritoneal cavity (lumboperitoneal [LP] shunt)⁸. There is currently no evidence to support the superiority of VP versus VA versus LP shunt systems. In adults, 15%-25%^9,10,11,12 of new VP shunts fail, typically within the first 6 months, and upward of 50% fail in high-risk populations¹³.VP shunt failure may be secondary to a shunt infection, valve malfunction, or catheter failure at the proximal or distal sites^{12,14,15,16,17}. Each shunt failure requires repeat surgery, which is associated with a cumulative risk for perioperative complications^18,19 and stress for patients and families, in addition to increased healthcare infrastructure costs^{20,21,22,23,24}.

The "traditional" VP shunt insertion technique involves freehand insertion of the proximal catheter using surface anatomical landmarks and placement of the distal catheter either via a mini-laparotomy or a trocar conduit^25,26,27. These techniques do not allow for real-time tracking or direct visualization of the final location during or after catheter insertion. Failure to achieve an ideal position for these catheters can lead to shunt failure, which is the most frequent long-term complication associated with VP shunt treatment of hydrocephalus^10,28. Proximal catheters typically fail due to malposition and/or subsequent occlusion by the choroid plexus tissues or intraventricular debris. The leading causes of distal catheter failure in adults include catheter mispositioning, migration, and/or occlusion by omental tissues, bowel, and intrabdominal debris or adhesions^{11, 28,29,30,31}.

There is recent evidence to suggest that the modification of VP shunt insertion techniques by placing the proximal and distal catheters under neuronavigation and laparoscopic guidance respectively, are associated with reduced risks of shunt failures^26,32,33. In addition, compliance with shunt infection reduction protocols has been shown to reduce the risks of shunt failure secondary to infections³⁴. Furthermore, Svoboda et al. described a "falciform technique" where the distal catheter was anchored to the falciform ligament and placed in the perihepatic space away from the omentum, which helped reduce the risk of catheter migration and obstruction by the omentum³⁵. To our knowledge, while the use of neuronavigation and laparoscopy have been independently assessed, their combined benefits have not been reported, and the surgical techniques have not been adequately described in the literature.

We recently completed a 7 year prospective quality improvement study that combined neuronavigation, laparoscopy, the falciform technique and a shunt infection reduction protocol in adult hydrocephalus patients³⁶. With our combined approach, the overall risk of shunt failure was reduced by 44%³⁶. The objective of this paper is to present a surgical video accompanied by a step-by-step guide of the operative techniques to promote a paradigm shift toward the use of these adjuncts to reduce the risks of shunt failures in adults.

The surgical approach presented here can be performed for any VP shunt insertion surgery. We describe the case of a 72-year-old male who was diagnosed with idiopathic normal pressure hydrocephalus (iNPH) and met the criteria for a VP shunt insertion³⁷. The patient presented with a 1 year history of progressive gait and cognitive impairment, with intermittent urinary incontinence. His past medical history was significant for hypertension and the surgical treatment of bladder cancer. A magnetic resonance imaging (MRI) brain evaluation of the patient showed ventriculomegaly with an Evan's index of 0.41. An MRI evaluation completed 4 years earlier did not demonstrate ventriculomegaly with an Evan's index of 0.29 (Figure 2). His neurological examination confirmed that he had a wide-based shuffling gait with low steppage and an abnormally slow gait velocity of 0.83 m/s. He had no signs of myelopathy. His Montreal Cognitive Assessment (MoCA) version 7.1 score was 22/30, which confirmed his mild-moderate cognitive impairment. After a 3 day external lumbar drain (ELD) trial with hourly CSF removal to test CSF removal symptom responsiveness, his gait velocity improved to 1.2 m/s and his MoCA score increased by 3 points.

Protocol

The following protocol follows the guidelines of the University of Calgary Conjoint Health Research Ethics Board. Informed media consent for the procedure was obtained and the patient provided written consent for this publication.

1. Positioning and pre-procedure setup

1. Obtain a preoperative cranial MRI or computed tomography (CT) with the appropriate neuronavigation protocol.
2. Place the patient supine on a donut headrest with the head turned toward the contralateral side and place a shoulder roll to augment the exposure of the occipital region (Figure 3).
3. Upload the patient's preoperative cranial MRI or CT, register it to the neuronavigation system, and complete the neuronavigation workstation planning.
4. Select an entry point and target for the proximal catheter and mark the specific entry location on the patient's scalp.
   NOTE: By standard, a right-sided posterior approach is preferred, unless precluded by the patient's circumstances. An ideal entry point is one with a trajectory that traverses minimal parenchyma while missing any identifiable vessels in its path to the body of the right lateral ventricle (Figure 3).
5. Mark an inverted u-shaped (horseshoe-shaped) incision to incorporate the entry point. Shave any hair surrounding the incision with a clipper (Figure 3).
6. Mark a 1 cm para-midline abdominal incision at the junction, immediately inferior and right lateral to the xiphisternum.
7. Infiltrate the scalp incision with a local anesthetic.
8. Adhere to a strict infection-prevention protocol (bundle) (Figure 4)³⁸.
9. Prepare the entire surgical field with a 2% chlorhexidine gluconate/70% isopropyl alcohol solution and allow it to dry for at least 3 min before starting the operative draping.
   ​NOTE: Prior to operative draping, all scrubbed surgical staff must double glove, and must change their outer gloves for new ones after draping of the patient is completed.
10. Drape the entire surgical field with an antimicrobial incise drape, which will help hold the drapes in place and reduce the surgical team's direct contact with the skin.
11. Apply a standard laparoscopic drape and extend the opening in a cranial direction to the edges of the draping to allow exposure of the cranium and chest surgical field.

2. Cranial exposure

1. Use a #15 scalpel to score the horseshoe-shaped incision.
2. Use a fine-tip monopolar cautery to deepen the incision, making sure to preserve the periosteal layer.
3. Retract the skin edges with a self-retaining retractor.
4. Make a cruciate periosteal incision in the center of the wound to expose the skull using monopolar cautery.
5. Make an approximately 2 cm burr hole in the center of the periosteal exposure, ensuring the underlying dura is preserved (Figure 5).

3. Subcutaneous distal catheter placement

1. Make a para-midline sub-xiphisternum incision down to the perifascial fat layer.
2. Blunt dissect the subcutaneous tissue 2-3 cm in a cranial direction.
3. Carefully guide a tunneling stylet with its encasing plastic sheath within the subcutaneous layer and pass it toward the cranial incision, taking every caution to stay above the ribs and clavicle, and avoid piercing the skin.
4. Once the inferior aspect of the cranial incision is pierced by the tunneller, withdraw the stylet, leaving the plastic sheath in place (Figure 5).
5. Create a subgaleal pocket at the inferior edge of the cranial incision around the plastic sheath that is sizable enough to bury the shunt reservoir using monopolar cautery and blunt dissection with Kelly forceps.
6. Remove the distal catheter from the sterile packaging and place it in sterile saline.
7. Thread the distal catheter through the plastic sheath from cranial to caudal direction, minimizing contact of the shunt components with the drapes, and then remove the plastic sheath.
8. Prime the system with sterile saline solution to remove any air.
9. Valve attachment
   1. If a programmable shunt valve is used, program it to the desired setting before it is removed from the packaging. Remove the VP shunt valve and distal catheters from the sterile packaging and place the components in sterile saline.
   2. Attach the distal port of the valve to the proximal end of the distal catheter, secure it twice with 3-0 silk ties, and prime the system with sterile saline solution to remove any residual air locks. Wrap the valve and the exposed catheter in a saline-soaked sponge making every attempt to prevent the shunt system from touching the drapes.

4. Ventricular (proximal) catheter insertion

1. Remove the ventricular catheter from the sterile packaging and place it in sterile saline.
2. Create a small centrally located circular durotomy equivalent to the diameter of the proximal catheter (incorporating the underlying pia and arachnoid) using a fine tip monopolar cautery.
3. With the navigation stylet within the proximal catheter, pass the catheter into the ipsilateral ventricle using real-time navigation along the preprogrammed trajectory to the target depth.
   NOTE: Often, there is CSF flow at about 5 cm, however, ensure to advance the catheter further to a depth of approximately 8-10 cm (target).
4. Once at the target depth, remove the navigation stylet probe from the ventricular catheter and confirm free CSF flow. Then clamp the catheter with a snap using booties to protect the catheter.
5. Trim the proximal catheter, leaving about 2 cm extra from the outer table of the skull (Figure 5).
6. Attach the distal end of the proximal catheter to the proximal outlet of the valve and secure it twice with 3-0 silk ties.
7. Carefully place the valve into the subgaleal pocket and anchor the valve sleeve to the preserved periosteum with a 4-0 silk suture.
8. Apply gentle traction on the distal catheter at the abdominal incision to ensure no catheter kinks exist.
9. Confirm that the spontaneous flow of CSF is at the very distal (abdominal) end of the shunt system.

5. Intrabdominal (distal) catheter placement

NOTE: The distal catheter is placed laparoscopically within the peritoneal cavity, ideally by a general surgeon.

1. Make a curvilinear periumbilical incision with a #15 scalpel followed by blunt dissection down to the abdominal wall fascia.
2. Grasp the fascia on each side with Kocher forceps and incise it in a vertical fashion, to ensure entry into the peritoneal cavity.
3. Place #2 polyglactin stay sutures through the fascia on either side, then insert a blunt Hasson trocar.
4. Insufflate the abdomen with carbon dioxide (CO₂).
5. Insert a at 30° angled laparoscope through the Hasson trocar access port (Figure 6).
6. Place a 5 mm port in standard fashion under direct vision, usually on the left, but this may vary depending on the density and position of intraperitoneal adhesions (Figure 6).
7. Perform any lysis of adhesions, that may be required.
8. Make a small hole in the falciform ligament (from the left side of the ligament) using a combination of electrocautery and laparoscopic Metzenbaum scissors (Figure 6). The hole must be as close to both the liver and diaphragm as safely possible (cephalad).
9. Create a transverse abdominal tunnel for the VP shunt catheter using the electrocautery hook at the incision created in step 3.1 (where the distal catheter exits from the subcutaneous space).
10. Insert the distal VP shunt catheter into the peritoneal cavity through the path created with a 11F peel-away sheath introducer.
11. Once the catheter is visualized in the abdominal cavity, grasp and position it, through the hole in the falciform ligament (Figure 6).
12. Pull the remaining catheter through the falciform ligament hole from the right side and tuck it behind the liver (following medial mobilization of the right posterior liver sector). The catheter's final resting place must be the retrohepatic space (Figure 6).
13. Trim the catheter such that the end is located just above the inferior margin of the liver. The final position of the catheter should ideally be inferior to the diaphragm but superior and posterior to the mobilized liver, immediately superior to the right pericolic gutter. Confirm there is still spontaneous CSF flow through the catheter under direct visualization (Figure 6).
    NOTE: There is no predetermined length of the catheter. The catheter is trimmed to fit the patient's anatomy intracorporeally.
14. Remove the residual (trimmed part of the catheter) through the 5 mm side port.
15. Deflate the abdomen slowly and cautiously to ensure no migration of the catheter, and then remove all instruments.

6. Closure

1. Close the cranial wound in a layered fashion with 3-0 polyglactin simple interrupted buried sutures in the galea layer and staples in the skin. Apply a dressing.
2. Close the abdominal fascia using the previously placed polyglactin stay sutures followed by 4-0 poliglecaprone-25 subcuticular sutures and acrylate adhesive for skin closure. Apply a surgical dressing.

Results

On postoperative day #1, the patient presented in the video underwent a CT of the head and an x-ray of the abdomen (Figure 7). This imaging, respectively, demonstrated optimal proximal catheter placement in the right lateral ventricle and the location of the distal catheter in the peri-hepatic space. At the patient's 3-month and 1-year postoperative clinic assessments following placement of the VP shunt, his gait velocity had improved from a preoperative 0.83 m/s to 1.4 m/s and his MoCA ...

Discussion

Patients tolerate the procedure well, are extubated immediately postop and are suitable for non-acute wards for overnight monitoring. It has been our practice to obtain a plain CT scan of the head the next morning to confirm the proximal catheter placement and as baseline imaging for future management. In addition, we obtain an abdominal x-ray to confirm the postoperative position of the abdominal catheter. The majority of our patients are assessed by both occupational therapy and physiotherapy and deemed safe by allied ...

Materials

Name	Company	Catalog Number	Comments
30-degree angle laparoscope	Stryker	0502-937-030
Barium impregnated proximal catheter	Medtronic	41101
Bowel grasper	Richard Wolf	8393.25
Certas Valve inline	Codman	82-8800
Chloraprep	3M	355-S10325/103.25
Electrocautery	Karl Storz	28160KA
Frameless-based neuronavigation system with magnetic tracking (AxiEM)	Medtronic	9735428/9734887
Hasson trocar	Applied Medical Inc	C0R95
Ioban	3M	6661EZ
Monocryl	Ethicon	D8550
Open barium impregnated proximal catheter	Medtronic	23092
Pneumatic surgical drill	Medtronic	PM100
Steri-Strips	3M	R1547
Video System Endoscopy	Stryker	Not Available