Hydrodynamic properties of hydrocephalus shunts

Area of Science:

• Neurosurgery
• Biomedical Engineering
• Medical Devices

Background:

• Hydrocephalus shunt performance is not consistently characterized by manufacturers.
• Selecting the appropriate shunt requires matching its hydrodynamic properties to patient-specific cerebrospinal fluid (CSF) circulation profiles.
• There is a need for comprehensive evaluation of currently used shunts in the UK.

Purpose of the Study:

• To evaluate the hydrodynamic properties of the most common hydrocephalus shunts used in the UK.
• To provide neurosurgeons with crucial performance data for informed shunt selection.
• To compare the performance characteristics of various shunt models under different conditions.

Main Methods:

• Testing of ten common hydrocephalus shunt models, including Medtronik, Heyer-Schulte, Codman, and Cordis brands.
• Measurement of hydrodynamic resistance with and without connected distal catheters.
• Assessment of siphon-prevention mechanisms and susceptibility to external magnetic fields for programmable valves.

Main Results:

• The majority of tested shunts exhibit low hydrodynamic resistance, with exceptions including the PS Lumboperitoneal and Orbis-Sigma valves.
• Connecting a long distal catheter increases hydrodynamic resistance by 100-200% in most valves.
• Siphon-preventing mechanisms in some valves offer resistance to negative pressures but can be compromised by subcutaneous pressure. All programmable valves are prone to siphoning, and their settings can be altered by magnetic fields.

Conclusions:

• Hydrocephalus shunt performance, particularly hydrodynamic resistance and susceptibility to siphoning, varies considerably among models.
• Programmable shunts present risks of unintended setting changes and siphoning, requiring careful consideration.
• Informed shunt selection based on detailed hydrodynamic evaluation is critical for optimizing patient outcomes in hydrocephalus management.