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Thursday 07 April 2022

Headphone device uses eardrum to measure pressure on the brain

Southampton researchers are developing a new, safer way of measuring brain pressure that avoids the need to drill a hole in the skull.

The Babelfish study is part of a research programme that could help detect life-threatening head injuries and infections.

The results, published in the journal Physiological Measurement, establish the normal range of eardrum movements in healthy people.

This is an essential first step in the development of the new technique. Eardrum movements outside this range can now be used to detect dangerously high pressure on the brain.

Why measure pressure on the brain?

Most people will be familiar with having their blood pressure measured, but not many people know what it is like to have their brain pressure measured.

This is because currently the only ways to measure it are through a hole drilled in the skull or a needle inserted into the spinal canal, a procedure known as lumbar puncture.

A simple way to measure brain pressure would be invaluable for doctors to diagnose and monitor patients with conditions such as strokes, brain tumours and some types of dementia.

Measuring eardrum movements

A team of researchers at University Hospital Southampton, including Dr Tony Birch, Dr Robert Marchbanks and Diederik Bulters, has shown that brain pressure changes the way the eardrum moves.

They have done this using a very sensitive device for measuring eardrum movements, known as a cerebral and cochlear fluid pressure analyser.

The device measures movements of the eardrum. These are not the fast vibrations of the eardrum that allow us to hear sounds, but slower movements caused by the heart beating, breathing and by some tiny muscles that can contract and relax inside the ear.

The research has already been adopted by NASA to analyse brain pressure levels in astronauts. Potential use in the military could also distinguish between head injuries and post-traumatic stress disorder in soldiers.

Determining what is normal

The aim of the Babelfish study was to establish how the eardrum moves in healthy people.

Nobody has looked at this in a large number of people before. It is really important to know what is normal to tell if a patient has an unhealthy amount of pressure on their brain.

The researchers successfully determined a healthy range of eardrum movements, indicating normal pressure inside the skull.

Brain pressure and performance

The researchers also speculated that brain pressure might be related to brain performance, not just in people with abnormal brain pressure but in the general population.

To test this, they asked all volunteers to complete a short cognitive assessment test and found people with a better score had more movement of their eardrums. This discovery has been published in the journal Cerebral Circulation - Cognition and Behavior.

This might show that abnormal brain pressure is common in the healthy population, and reveal an unknown physical reason explaining why some people are not as sharp as they could be.

Dr Birch says: “The Babelfish study has been a great advance. We are continually learning more from the study data and making refinements that are making the measurements more accurate.

“We plan further studies to establish the most reliable use for the measurements to help patients.”