Hydrocephalus therapy: reduction of shunt occlusions using a peel-away sheath

Contactless Ultrasonic Cavitation for the Prevention of Shunt Obstruction in Hydrocephalus: A Proof-of-Concept Study

BACKGROUND

Obstructive failure of implanted shunts is the most common complication in the treatment of hydrocephalus. Biological material and debris accumulate in the inner walls of the valve and catheters block the normal flow of the drained cerebrospinal fluid causing severe symptoms with high morbidity and mortality. Unfortunately, at present, there is no effective preventive protocol or cleaning procedure available.

OBJECTIVE

To assess whether externally applied, focused ultrasound beams can be used to resuspend deposits accumulated in brain shunts safely.

METHODS

A computational model of an implanted brain shunt was implemented to test the initial design parameters of a system comprising several ultrasound transducers. Under laboratory conditions, configurations with 3 and 4 transducers were arranged in a triangle and square pattern with their radiation axis directed towards a target model of the device, 2 catheters and a brain shunt filled with water and deposited graphite powder. The ultrasound beams were then concentrated on the device across a head model.

RESULTS

The computational model revealed that by using only 3 transducers, the acoustic field intensity on the valve was approximately twice that on the brain surface suggesting that acoustic cavitation could be selectively achieved. Resuspension of graphite deposits inside the catheters and the valve were then physically demonstrated and video-recorded with no temperature increase.

CONCLUSION

The technology presented here has the potential to be used routinely as a noninvasive, preventive cleaning procedure to reduce the likelihood of obstruction-related events in patients with hydrocephalus treated with an implanted shunt.

Benefits of Endoscopic Sheath in Intraventricular Neuroendoscopy: Technical Note

BACKGROUND

 The usefulness of the endoscopic sheath is underreported in the literature.

OBJECTIVE AND METHODS

 To explain the use of an endoscopic sheath and to highlight its benefits.

RESULTS

 In addition to protecting the surrounding brain parenchyma when inserting the endoscope, the endoscopic sheath is a very useful tool to retract neurovascular structures, achieve hemostasis, and create adequate working space within narrow ventricles. The sheath can be moved within the ventricular system, and the endoscope can be moved independently within the sheath. These movements represent all the advantages of the endoscopic sheath.

CONCLUSIONS

 We used an endoscopic sheath in ∼ 300 intraventricular neuroendoscopic procedures and consider the sheath an essential part of a ventriculoscopic system. Proper use of the sheath can help avoid or manage endoscopic complications.

Next generation of ventricular catheters for hydrocephalus based on parametric designs

BACKGROUND

The flow pattern of the cerebrospinal fluid is probably the most important factor related to obstruction of ventricular catheters during the normal treatment of hydrocephalus. To better comprehend the flow pattern, we have carried out a parametric study via numerical models of ventricular catheters. In previous studies, the flow was studied under steady and, recently, in pulsatile boundary conditions by means of computational fluid dynamics (CFD) in three-dimensional catheter models.

OBJECTIVE

This study aimed to bring in prototype models of catheter CFD flow solutions as well to introduce the theory behind parametric development of ventricular catheters.

METHODS

A preceding study allowed deriving basic principles which lead to designs with improved flow patterns of ventricular catheters. The parameters chosen were the number of drainage segments, the distances between them, the number and diameter of the holes on each segment, as well as their relative angular position.

RESULTS

CFD results of previously unreleased models of ventricular catheter flow solutions are presented in this study. Parametric development guided new designs with better flow distribution while lowering the shear stress of the catheters holes. High-resolution 3D printed catheter solutions of three models and basic benchmark testing are introduced as well.

CONCLUSIONS

The next generation of catheter with homogeneous flow patterns based on parametric designs may represent a step forward for the treatment of hydrocephalus, by possibly broadening their lifespan.

Novel type of peritoneocentesis trocar-assisted distal ventriculoperitoneal shunt placement with supervision via a one-port laparoscope

Ventriculoperitoneal shunts (VPS) are the primary treatment for hydrocephalus and are associated with a high risk of complications, specifically in patients who are obese or have abdominal adhesions or shunt revisions. The present study describes the use of a novel type of peritoneal catheter peritoneocentesis trocar insertion with the assistance of a one-port laparoscope. A total of 36 patients with hydrocephalus underwent this novel type of peritoneocentesis trocar-assisted VPS. The distal shunt catheter was placed into the right subdiaphragmatic space and the catheter was traversed through a single hole drilled through the liver falciform ligament. The duration of the laparoscopic surgery ranged from 6–18 min (mean 10.4±1.6 min). No shunt-related infections or catheter malfunctions or injuries to the intra-abdominal organs occurred. The total abdominal incision length was 1.0 cm (0.5+0.5 cm). No laparoscopy-related complications were observed during follow-up assessments. The novel approach used in the current study is very easy to perform, and this method may significantly reduce the risk of malfunction complications. The presented method also has the advantages of reduced trauma and a simpler surgery. The current study indicated that this simple, minimally invasive procedure was beneficial for patients with hydrocephalus, specifically in cases of patients with obesity, peritoneal adhesions or shunt revisions.

Basic cerebrospinal fluid flow patterns in ventricular catheters prototypes

OBJECT

A previous study by computational fluid dynamics (CFD) of the three-dimensional (3-D) flow in ventricular catheters (VC) disclosed that most of the total fluid mass flows through the catheter's most proximal holes in commercially available VC. The aim of the present study is to investigate basic flow patterns in VC prototypes.

METHODS

The general procedure for the development of a CFD model calls for transforming the physical dimensions of the system to be studied into a virtual wire-frame model which provides the coordinates for the virtual space of a CFD mesh, in this case, a VC. The incompressible Navier-Stokes equations, a system of strongly coupled, nonlinear, partial differential conservation equations governing the motion of the flow field, are then solved numerically. New designs of VC, e.g., with novel hole configurations, can then be readily modeled, and the corresponding flow pattern computed in an automated way. Specially modified VCs were used for benchmark experimental testing.

RESULTS

Three distinct types of flow pattern in prototype models of VC were obtained by varying specific parameters of the catheter design, like the number of holes in the drainage segments and the distance between them. Specifically, we show how to equalize and reverse the flow pattern through the different VC drainage segments by choosing appropriate parameters.

CONCLUSIONS

The flow pattern in prototype catheters is determined by the number of holes, the hole diameter, the ratio hole/segment, and the distance between hole segments. The application of basic design principles of VC may help to develop new catheters with better flow circulation, thus reducing the possibility of becoming occluded.

Does CT wand guidance improve shunt placement in patients with hydrocephalus?

OBJECT

To evaluate the effectiveness of stereotactic navigation in enhancing the accuracy of ventricular shunt placement in patients with hydrocephalus.

METHODS

A retrospective cohort study at a single institution by a single surgeon was performed. Consecutive patients who underwent implantation of a ventricular shunt for the management of hydrocephalus between July 2001 and December 2011 were included in the study, totaling 535 patients. Patients were classified as either having optimal or sub-optimal placement of the shunt into the ventricle. Multiple logistic regression analysis was used.

RESULTS

Overall, 93.8% of patients were found to have optimal shunt placement. On multivariate analysis, navigation use was not significantly associated with improved accuracy of shunt placement (odds ratio [OR] = 0.54; 95% confidence interval [CI] = 0.19-1.54; p = 0.25). Pseudotumor cerebri diagnosis was significantly associated with increased odds of sub-optimal shunt placement (OR = 6.41; 95% CI = 1.90-21.59; p=0.003).

CONCLUSIONS

CT guided navigation did not significantly improve the accuracy of ventricular shunt placement in adults with hydrocephalus for an experienced surgeon. Further studies are required to assess the utility of CT guided navigation for less experienced surgeons and patients with small or dysmorphic ventricles.

What We Should Know About the Cellular and Tissue Response Causing Catheter Obstruction in the Treatment of Hydrocephalus

The treatment of hydrocephalus by cerebrospinal fluid shunting is plagued by ventricular catheter obstruction. Shunts can become obstructed by cells originating from tissue normal to the brain or by pathological cells in the cerebrospinal fluid for a variety of reasons. In this review, the authors examine ventricular catheter obstruction and identify some of the modifications to the ventricular catheter that may alter the mechanical and chemical cues involved in obstruction, including alterations to the surgical strategy, modifications to the chemical surface of the catheter, and changes to the catheter architecture. It is likely a combination of catheter modifications that will improve the treatment of hydrocephalus by prolonging the life of ventricular catheters to improve patient outcome.

Use of a new type of trocar for the surgical treatment of hydrocephalus: a simple and effective technique

This study compared the use of a new type of peritoneocentesis trocar with conventional laparotomy for the placement of the distal catheter in the treatment of hydrocephalus with ventriculoperitoneal shunt. A total of 376 patients with hydrocephalus were recruited to the study and were assigned randomly to undergo insertion of the distal catheter by conventional laparotomy (n = 195) or using the new peritoneal trocar (n = 181). The time taken for the surgical procedure and the complication rate over the following 1-year period were compared between the two groups. The mean length of the procedure to place the distal catheter was significantly shorter in the trocar group compared with the laparotomy group. Infection and obstruction rates were significantly higher in the laparotomy group than in the trocar group. In conclusion, the use of the new trocar was associated with lower rates of surgically induced trauma and complications compared with conventional laparotomy.

Ventricular catheter exchange using a peel-away outer catheter

Ventricular catheter replacement can be challenging, especially in patients with small ventricles. Shunt malfunction due to ventricular catheter obstruction can occur without ventricular enlargement, such as in the setting of slit-ventricle syndrome or benign intracranial hypertension. The authors describe a simple technique for ventricular catheter exchange using a peel-away catheter. In the limited initial experience of the senior author (G.S.C.), this technique appears to be safe and effective. To the authors' knowledge, this method has not been described in the neurosurgical literature before.

Can using a peel-away sheath in shunt implantation prevent ventricular catheter obstruction?

PURPOSE

Shunt obstruction is the most common shunt complication. In 2003, Kehler et al. used peel-away sheath while implanting the ventricular catheter in 20 patients. They found less revision rate in the peel-away sheath group. We aimed to test the efficacy of this technique in cadavers.

METHODS

We used 100 fresh brains obtained from medicolegal autopsies. Posterior parietal and frontal approaches were used to puncture the lateral ventricle in each cerebral hemisphere. The ventricle is punctured with a peel-away sheath system. After the ventricle is reached, the mandarin is retracted and the ventricular catheter is introduced through the opening. The ventricular catheter was removed from the ventricle, the opening at the tip of the ventricular catheter was checked out for obstruction, and the number of patent and plugged openings was recorded. This procedure was repeated four times for each location with and without using peel-away sheath. The control group consisted of the procedures done without using peel-away sheath.

RESULTS

The number of the plugged openings in the peel-away sheath group was significantly smaller than the control group. There was no significant difference between the two groups in terms of gender and left and right cerebral hemispheres. The obstruction rate was significantly lower in the posterior parietal approach. Pearson's correlation showed that increasing age was associated with less obstruction rate.

CONCLUSION

Peel-away sheath decreases the number of plugged openings of the ventricular catheter. A clinical cooperative study is needed to prove that a peel-away sheath should be included in the ventricular shunt systems in the market.

New transparent peel-away sheath with neuroendoscopic orientation markers

✓The peel-away sheath in neuroendoscopic surgery offers numerous advantages and has many potential applications. However, currently available nontransparent sheaths have a critical disadvantage in that disorientation can occur, given the limited visible operative field. To overcome this obstacle, the authors have developed and clinically applied a new transparent sheath with “navigational orientation markers.” The clear peel-away sheath provides a transparenchymal route, parenchymal protection, and, most importantly, direct visualization of the surroundings along the whole trajectory and at the distal edge. The navigational orientation markers add further benefits in terms of facilitating orientation in the endoscope trajectory, making this tool extremely useful in neuroendoscopic surgery.