Gravitational Shunt Valves Explained: How Position-Dependent Valves Reduce Over-Drainage

· NJM Medical Editorial Team

Why a standing patient drains more CSF than a lying one — and how gravitational and adjustable valves such as the MIETHKE GAV and proGAV 2.0 address it.

A ventriculoperitoneal (VP) shunt drains excess cerebrospinal fluid (CSF) from the brain’s ventricles to the abdomen. The valve in that system decides when and how much fluid flows — and choosing the right valve is one of the most important decisions in hydrocephalus treatment.

The over-drainage problem

When a patient stands up, the height difference between the head and the abdomen adds a hydrostatic “siphoning” pressure. A conventional differential pressure valve cannot tell whether the patient is lying or standing, so in the upright position it may drain too much CSF. Over-drainage can cause headaches, slit ventricles or subdural collections.

How a gravitational valve helps

A gravitational valve contains a unit that reacts to body position — typically a set of balls in a titanium housing. When the patient is horizontal, the gravitational unit opens and the differential pressure unit alone sets the opening pressure. When the patient is upright, the gravitational unit closes and adds extra resistance, counteracting the siphoning effect.

  • GAV® — MIETHKE’s gravity-assisted valve for adults.
  • paediGAV — a position-dependent valve designed for children.
  • miniNAV® — a very small differential pressure valve for flexible shunt configurations.

Adjustable valves: changing the setting without surgery

Patients’ needs change over time. Adjustable valves such as the proGAV 2.0 let the clinician change the opening pressure non-invasively using an adjustment instrument. According to the manufacturer, proGAV 2.0 is MRI compatible up to 3 Tesla and its “Active-Lock” mechanism protects the setting from everyday magnets. M.BLUE goes further by adapting to the patient’s activity across day and night.

Reducing infection risk

Shunt infection remains a major cause of revision surgery. Antibiotic-impregnated catheters such as XABO are designed to reduce the risk of bacterial colonisation of the catheter.

Talk to us

NJM Medical supplies MIETHKE shunt systems and accessories and supports neurosurgical teams with product information and training. Get in touch to discuss the right configuration for your patients.

This article is for general information for healthcare professionals and is not medical advice. Device selection and settings must always follow the manufacturer’s instructions for use and the treating clinician’s judgement.