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

Introduction We described the case of a 72 year old male who was diagnosed with idiopathic normal pressure hydrocephalus, or iNPH, who met the criteria for insertion of a ventricular peritoneal shunt. The patient presented with a one year history of progressive gait and cognitive impairment and intermittent urinary incontinence. His past medical history was significant for hypertension and the surgical treatment of bladder cancer.

A magnetic resonance imaging, or MRI, of the brain showed ventriculomegaly with an Evans index of 0.41. An MRI evaluation completed four years earlier did not demonstrate ventriculomegaly and had an Evans index of 0.29. His neurological examination confirmed he had a wide-based shuffling gait with low steppage and an abnormally slow gait velocity of 0.83 meters per second.

He had no signs of myelopathy. His Montreal Cognitive Assessment, or MoCA, was 22 out of 30, which confirmed his mild to moderate cognitive impairment. A three day External Lumbar Drain, also known as an ELD trial, with hourly CSF removal, was done to test CSF removal symptom responsiveness.

After the ELD trial, his gait velocity improved to 1.2 meters per second, and his MoCA score increased by three points. Given the positive response to temporary CSF removal, the patient was offered ventriculoperitoneal shunt surgery. The protocol and videos presented follow the guidelines of the University of Calgary Conjoint Health Ethics Research Board and an informed media consent was obtained, and the patient provided written consent to this publication.

Protocol The surgical approach presented here can be performed for any ventriculoperitoneal shunt insertion surgery. Positioning and pre-procedure set-up Place the patient supine on a donut headrest, with the head turned towards the contralateral side, and then place a shoulder roll to augment exposure of the occipital region. Obtain a preoperative cranial MRI or computed tomography, or CT, with an appropriate neuronavigation protocol.

Upload the patient's pre-operative cranial MRI or CT, and register to the neuronavigation system and complete the neuronavigation workstation planning. Select an entry point and target for the proximal catheter. Mark the selected entry site location on the patient's scalp.

By standard, a right-sided posterior approach is preferred unless precluded by the patient's circumstances. Mark an inverted U-shaped or horseshoe shaped incision to incorporate the entry point. Shave any hair surrounding the incision with a clipper.

Infiltrate the scalp incision with a local anesthetic. Prep the entire surgical field with a 2%chlorhexidine gluconate and alcohol solution. A strict infection prevention protocol, often referred to as a bundle, must be adhered to.

Prior to operative draping, all scrubbed surgical staff must double glove, and change their outer gloves for a new pair after draping the patient has been completed. Drape the entire surgical field with an antimicrobial incise drape, which can also help hold the drapes in place and reduce surgical team direct contact with skin. 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 the chest surgical fields.

Cranial exposure Use a number 15 scalpel to score the horseshoe shaped incision. Use a fine tip monopolar cautery to deepen the incision, making sure to preserve the periosteal layer. Retract the skin edges with a self retaining retractor, and make a cruciate periosteal incision in the center to expose the skull using monopolar cautery.

Make an approximately two centimeter burr hole in the center of the periosteal exposure, ensuring the underlying dura is preserved. Subcutaneous Distal Catheter Placement Make a paramidline sub-xiphisternum incision down to the perifascial fat layer. Blunt dissect the subcutaneous tissue for 2-3 centimeters in the cranial direction.

Carefully guide a tunneling stylet within 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. Once the inferior aspect of the cranial incision is pierced by the tunneler, withdraw the stylet, leaving the plastic sheath in place. Create a subgaleal pocket at the inferior edge of the cranial tissue around the plastic sheath that will be sizeable enough to bury the shunt valve.

Use monopolar cautery and blunt dissection with the Kelly forceps. Remove the distal catheter from the sterile packaging and place it in sterile saline. Thread the distal catheter through the tunnel plastic sheath from the cranial to the caudal direction, minimizing contact of the shunt components to the drapes, and then remove the plastic sheath.

Prime the system with sterile saline to remove any air. Valve attachment If a programmable shunt valve is used, it should be programmed to the desired setting before it is removed from the packaging and before it is passed into the operative field. Just before use, remove the valve from its sterile packaging and place it into sterile saline, and prime it with the sterile saline.

Attach the distal port of the valve to the proximal end of the distal catheter. Secure the catheter twice with silk ties, and prime the system with sterile saline to remove any residual air. Ventricular or proximal catheter insertion Just before it is needed, remove the ventricular catheter from a sterile packaging, and place it into sterile saline.

Create a small, centrally-located, circular durotomy, equivalent to the diameter of the proximal catheter that incorporates the underlying pia and arachnoid. Use the fine tip, or needle tip, monopolar cautery to do this. Place the navigation stylet within the proximal catheter, and pass the catheter into the ipsilateral ventricle, using real-time navigation along the pre-programmed trajectory to the target depth.

Often there is CSF flow at about five centimeters of depth. However, it is appropriate to advance the catheter to a depth of approximately 8 to 10 centimeters. Once at the target depth remove the stylet from the ventricular catheter, and confirm that there is free flow of CSF.

At this point, clamp the catheter with a snap, using booties to protect the catheter. Trim the proximal catheter, leaving about two centimeters extra from the edge of the outer table of the skull. Attach the distal end of the proximal catheter to the proximal outlet of the valve, and secure it with two silk ties.

Carefully place the valve into the subgaleal pocket, and anchor the valve sleeve to the preserved periosteum with 4-0 silk suture. Apply gentle traction on the distal catheter at the abdominal incision to ensure no catheter kinks exist. Confirm spontaneous CSF flow at the distal end of the shunt system.

Intraabdominal, or distal, catheter placement The distal catheter is placed laparoscopically within the peritoneal cavity, ideally by a general surgeon. Make a curvilinear periumbilical incision with a 15 blade scalpel, followed by blunt dissection down to the abdominal wall fascia. Grasp the fascia on each side with coker forceps, and incise it in a vertical fashion to ensure entry into the peritoneal cavity.

Place 2 Polyglactin stay sutures through the incised fascia on the other side, and then insert a blunt Hassan trocar. Insert a 30 degree angle laparoscope through the Hassan trocar access port. Place a five millimeter port in standard fashion under direct vision, usually on the left, but this position may vary depending on the density and position of the interperitoneal adhesions.

Perform any lysis of adhesions that may be required. Make a small hole in the falciform ligament from the left side of the ligament, using a combination of electrocautery and laparoscopic Metzenbaum scissors. The hole in the falciform ligament must be made as close to liver and diaphragm as possible, to allow adequate and proper positioning of the catheter.

Using the electrocautery hook, create a transverse abdominal tunnel through the previously created sub-xiphisternum incision, where the distal VP catheter exits through the subcutaneous space. Insert the distal peritoneal shunt catheter into the peritoneal cavity through the path created with an 11 French Peel-Away Sheath Introducer. Once the catheter is visualized in the abdominal cavity with the laparoscope, grasp it and position it through the hole in the falciform ligament.

The catheter should be trimmed laparoscopically to fit the patient's anatomy and position the catheter as described. It should be noted that there is no predetermined length of the catheter. The catheter's final resting place must be in the retro-hepatic space.

The final position of the catheter should ideally be inferior to the diaphragm and superior and posterior to the mobilized liver. It should be immediately superior to the right paracolic gutter. CSF flow through the catheter can be confirmed by direct visualization with the laparoscope.

Remove the residual trimmed portion of the catheter through the five millimeter port. Deflate the abdomen slowly and cautiously to ensure no migration of the catheter occurs. Then remove all the instruments.

Wound closure Close the cranial wound in a layered fashion. Use 3-0 Polyglactin simple interrupted varied sutures in the galeal layer and staples for the skin layer. Close the abdominal fascia using the previously placed polyglactin stay suture, followed by 4-0 poliglecaprone 25 subcuticular sutures and acrylic adhesive for skin closure.

Apply a surgical dressing. Representative results On postoperative day one, the patient presented in this video underwent a CT of the head, and X-ray of the abdomen. The CT of the head demonstrated optimal placement of the proximal catheter within the right lateral ventricle.

The abdominal X-ray demonstrated the distal catheter was in the peri-hepatic space. At the patient's three month and one year postoperative clinic assessment, following the placement of the VP shunt, his gait velocity had improved from a preoperative 0.83 meters per second to 1.4 meters per second. His MoCA score had normalized at 29 over 30 from a preoperative score of 22.

The feasibility and patient outcomes of the surgical approach presented here were examined in a seven year prospective continuous quality improvement study, which has now been reported in the Journal of Neurosurgery. Summarizing that report, 224 consecutive adult patients were enrolled at a tertiary center. The primary objective was to determine the combined role of cranial intraoperative navigation and laparoscopy with a shunt infection prevention strategy to reduce the incidence of VP shunt insertion failure.

Of these patients, 115 underwent VP shunt insertion without neuronavigation and/or laparoscopic assistance, and 129 patients were treated with the surgical approaches presented here. We found that, with a background of shunt infection reduction protocols, combined neuronavigation and laparoscopy, was associated with reduction of overall shunt failure rates from 37%to 14%at one year, 45%to 22%at two years, and 51%to 29%at three years, with a hazard ratio of 0.44. There were no proximal catheter failures when neuronavigation was used.

The two year rates of distal catheter failure were 42%for those that did not undergo the combined neuronavigation laparoscopy-guided surgery, compared to only 20%among those patients that did undergo the combined neuronavigation laparoscopy-guided VP shunt surgery. Conclusion A combination of shunt infection and reduction strategies, neuronavigation, and laparoscopy techniques in adult VP shunt surgery can significantly improve shunt failure-free patient outcomes. In this protocol, we combined all three strategies, including anchoring the distal catheter to the falciform ligament to assist placement in the retro-hepatic space away from the Omentum.

We observed a decreased rate of infection, and a 44%reduction in the risk of overall shunt failure over time.