Flat-Bottom vs Burr-Hole Shunt Valves: Defit and Decurve Compared

A flat-bottom shunt valve lies flat against the skull beneath the scalp, along the route of the shunt, while a burr-hole valve is round and sits over the burr hole through which the ventricular catheter enters. DESU makes one of each: Defit, a flat-bottom silicone valve in three sizes, and Decurve, a round burr-hole silicone valve with a reservoir in paediatric and adult sizes.

Both belong to DESU’s fixed-pressure shunt systems, and both contain no metal. The practical difference is geometry, and geometry drives where and how the valve is placed. For a broader overview of valve types, see hydrocephalus shunt valve solutions.

What is a flat-bottom shunt valve?

A flat-bottom valve has an elongated body with a flat underside, designed to rest on the outer surface of the skull. Because it is separate from the burr hole, the ventricular catheter runs from the burr hole to the valve, and the valve then connects to the peritoneal catheter.

Defit is DESU’s flat-bottom valve. It has a silicone body, contains no metal and is offered with low, medium and high fixed pressures in three sizes:

The thickness column is often the one surgeons look at first, because it describes how far the valve will stand above the skull under the scalp.

What is a burr-hole shunt valve?

A burr-hole valve has a round body designed to be placed at the burr hole itself. The ventricular catheter and the valve meet at the same site, so the entry point and the valve location are combined.

Decurve is DESU’s burr-hole valve. Its round body is made of polypropylene and silicone elastomer, includes a reservoir, contains no metal and is offered with low, medium and high fixed pressures in two sizes: a paediatric Decurve with a 23 mm nominal diameter and an adult Decurve with a 28 mm nominal diameter.

How do Defit and Decurve compare side by side?

How does valve shape affect placement?

Valve shape changes the layout of the proximal part of the shunt. Technique and valve position are decided by the surgeon according to the instructions for use.

• One site or two: a burr-hole valve sits where the catheter enters the skull, while a flat-bottom valve is positioned away from the burr hole along the shunt route.
• Catheter path: with a flat-bottom valve, the ventricular catheter has to turn from the burr hole towards the valve. DESU kits include a right-angled connector, which orients the catheter at an appropriate angle and helps prevent kinking and clogging (see the L-type catheter connector).
• Profile: a flat-bottom valve’s height above the skull is set by its thickness, from 4.5 mm on the Ultra Small Defit to 7 mm on the Regular. A burr-hole valve’s footprint is set by its diameter.
• Soft-tissue cover: scalp thickness varies widely between infants and adults, and surgeons weigh how much tissue will cover the valve when choosing size and position.

What does the Decurve reservoir add?

A shunt reservoir is a chamber in the system that gives the clinical team a defined point of access to the shunt. Whether and how the Decurve reservoir is accessed in a given patient is set out in its instructions for use and decided by the treating team.

For buyers, the practical point is that the reservoir is part of the Decurve valve itself, so there is no separate reservoir to order.

What do Defit and Decurve have in common?

Apart from shape, the two families are built around the same kit logic, which makes them easy to stock together:

• Fixed low, medium and high pressure options.
• No metal; both suitable for MRI and CT.
• VP kits with a 23 cm ventricular catheter (1.3 mm inner, 2.5 mm outer diameter), a 120 cm peritoneal catheter (1.1 mm inner, 2.5 mm outer diameter), a stylet and a right-angled connector.
• An optional antisiphon device, with kit codes ending in “-ASD”.
• Antibiotic-impregnated configurations, where the antibiotic is impregnated into the material and released in a controlled manner over 28 days. Impregnated catheters are orange, standard ones white.
• Single-use, sterilised by ethylene oxide, manufactured under ISO 13485 and CE marked.

How do surgeons choose between them?

In practice the decision usually starts with where the surgeon plans to put the valve, then moves to size:

• Preferred valve position: at the burr hole, or separate from it on the skull.
• Patient size and scalp cover: which Defit thickness or Decurve diameter suits the patient.
• Need for a reservoir in the valve itself.
• Pressure category: low, medium or high, since both families are fixed-pressure. If the team wants an adjustable valve, that points to the Depus family instead.
• Antisiphon and antibiotic-impregnated configuration.

Surgeons who habitually use one approach will often default to that valve. Departments with several surgeons, or a mixed paediatric and adult case load, commonly stock both. For a wider view of how shunt type relates to the kind of hydrocephalus, see which shunt is right for different types of hydrocephalus.

Talk to a DESU product specialist

DESU can help you compare Defit and Decurve configurations, sizes and kit codes for your department. Write to sales@desu.tr, use the contact page, or request a quote.