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Change in ventricular size and effect of ventricular catheter placement in pediatric patients with shunted
1Division of Neurosurgery, The Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Shunt valve design did not impact shunt failure rates in pediatric hydrocephalus. Optimal catheter placement and environment are key to reducing shunt malfunction, not valve type alone.
Area of Science:
- Neurosurgery
- Pediatric Hydrocephalus Research
- Biomedical Engineering
Background:
- Cerebrospinal fluid (CSF) shunts are crucial for managing hydrocephalus in children.
- Previous studies indicated no significant difference in shunt failure rates among different valve designs.
- However, factors beyond valve design, such as catheter placement, may influence shunt performance.
Purpose of the Study:
- To investigate factors affecting shunt failure in pediatric hydrocephalus, beyond valve design.
- To identify strategies for reducing shunt malfunction through post hoc analysis of a randomized trial.
- To evaluate the impact of ventricular catheter tip location and environment on shunt outcomes.
Main Methods:
- A post hoc analysis of a multicenter, randomized trial involving 344 pediatric patients.
- Ventricular size was measured using a modified Evans' ratio at multiple intervals.
- Ventricular catheter tip location and environment were categorized, and Cox models analyzed failure risk.
Main Results:
- Ventricular size decreased over time, plateauing at 14 months, with no significant difference between the three valve designs.
- Frontal and occipital catheter tip locations were associated with a lower risk of shunt failure.
- Catheter tips surrounded by CSF or touching brain tissue significantly reduced failure risk, while myelomeningocele and large ventricles increased it.
Conclusions:
- Current shunt valve designs do not significantly alter the decline of ventricular size over time.
- The mechanical models underlying current shunt valve designs may be insufficient.
- Accurate ventricular catheter placement and improved valve designs controlling ventricular size are crucial for reducing shunt malfunction.
Objective:
The multicenter, randomized pediatric cerebrospinal fluid shunt valve design trial found no difference in the rate of shunt failure between a standard valve, a siphon-reducing valve (Delta; Medtronic PS Medical, Goleta, CA), and a flow-limiting valve (Orbis Sigma; Cordis, Miami, FL); however, the valves were expected to have different effects on ultimate ventricular size. Also, the catheter position or local environment of the ventricular catheter tip might have affected shunt failure. Therefore, we performed a post hoc analysis to understand what factors, other than valve design, affected shunt failure and to identify strategies that might be developed to reduce shunt failure.
Methods:
Ventricular size was measured at as many as six different intervals, using a modified Evans' ratio (with incorporation of the frontal and occipital dimensions), in 344 patients. Ventricular catheter location was defined as being in the frontal horn, occipital horn, body of the lateral ventricle, third ventricle, embedded in brain, or unknown. The ventricular catheter tip was described as surrounded by cerebrospinal fluid, touching brain, or surrounded by brain parenchyma within the ventricle (slit ventricle). Repeated measures analysis of variance for unbalanced data was used to analyze ventricular size. A Cox model (with incorporation of time-dependent covariates) was used to evaluate the contribution of age, etiology, shunt design, ventricular size, ventricular catheter location, and environment among the cases.
Results:
Ventricular volume decreased in an exponential fashion, forming a plateau at 14 months, and was similar for the three valves (P = 0.4). Frontal and occipital ventricular catheter tip locations were associated with a reduced risk of shunt failure (hazard ratios, 0.60 [P = 0.02] and 0.45 [P = 0.001], respectively). Ventricular catheter tips surrounded by cerebrospinal fluid or touching the brain were associated with a reduced risk of failure (hazard ratios, 0.21 and 0.33, respectively; P = 0.0001). Patients with myelomeningocele or large ventricles had increased risk of malfunction (hazard ratios, 1.78 [P = 0.006] and 2.33 [P = 0.03], respectively).
Conclusion:
Decline of ventricular size over time is not affected by these different shunt valve designs. This suggests that the mechanical models of hydrocephalus on which the designs were based are inadequate. Ventricular catheter tip location and ventricular catheter environment are important. Techniques to accurately place ventricular catheters and new valve designs that effectively control ventricular size might reduce shunt malfunction.