Designing a pressure sensor for the brain

Researchers at the Auckland Bioengineering Institute are working on what they hope will be the first New Zealand designed Class 3 medical device - a pressure sensor for the brain, to help people with hydrocephalus. The team explain the sensor design, how it works and how they test it.

Feeling the pressure

Professor Simon Malpas and his lab group are dedicated to figuring out how to detect pressure in the brain; pressure caused by a build-up of fluid, a condition known as hydrocephalus. But it's pressure of another kind that gets Malpas and his team out of bed every morning and drives them on.

"We often meet patients and their families, and neurosurgeons as well, and a common thing they say is, if you can get this to work, its a game-changer for their lives"

Malpas has been interested in how you detect pressure inside the body for many years, but these days he and his colleagues at the Auckland Bioengineering Institute are trying to invent a new kind of implantable brain pressure sensor to help hydrocephalus patients. If they can, it will be the first New Zealand designed Class 3 medical device.

In New Zealand medical devices are rated by their potential risk from Class 1 (low risk) upwards. A Class 3 device is something that is long term implanted in the body, and is, therefore, high risk (for example, a cardiac stent).

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In hydrocephalus, a build-up of fluid around the brain increases the pressure, which can impact brain function, cause brain damage, and can even cause death. Normally, about half a litre of cerebrospinal fluid is produced in the body each day. The fluid flows through cavities in the brain called ventricles, and bathes the brain and spinal cord, before being reabsorbed into the bloodstream. An imbalance of this - either by overproduction of fluid, or blockage of the absorption back into the bloodstream - can result in a build up. While it can affect anyone at any age, hydrocephalus is most common in infants and other adults.

Before the invention of an implantable shunt to drain this fluid, hydrocephalus was almost universally fatal. But unfortunately, the shunts commonly used today are still failure-prone - in children the failure rate is 30 - 40% at one year and about 50% at two years. This can be due to a variety of reasons, including infection, blockage and mechanical failure. Some of the most common early symptoms of a shunt failing are nausea and headache, which can create a lot of uncertainty and anxiety amongst patients and their families. Is the headache they are experiencing due to shunt failure, or something more innocuous?…

Go to this episode on rnz.co.nz for more details