Many individuals over age 65 suffer from dizziness and problems with balance; however, tests to identify the causes of such problems are often painful and can risk hearing damage. Now, researchers from Chalmers University of Technology have developed a new testing device using bone conduction technology that is said to offer “significant advantages” over current tests, the Sweden-based university announced. 

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Potentials (VEMP) test uses loud sounds to evoke a muscle reflex contraction in the neck and eye muscles, triggered by the vestibular system—the system responsible for our balance. The Chalmers researchers have now used bone-conducted sounds to achieve what they say are better results.

“We have developed a new type of vibrating device that is placed behind the ear of the patient during the test,” said Bo Håkansson, a professor in the research group ‘Biomedical signals and systems’ at Chalmers.

The vibrating device is small and compact in size, and optimized to provide an adequate sound level for triggering the reflex at frequencies as low as 250 Hz. Previously, no vibrating device has been available that was directly adapted for this type of test of the balance system.

In bone-conduction transmission, sound waves are transformed into vibrations through the skull, stimulating the cochlea within the ear, in the same way as sound waves go through the ear canal, the eardrum, and the middle ear. Håkansson has over 40 years of experience in this field and has previously developed hearing aids using this technology.

The cause of dizziness can be difficult to diagnose for several reasons. In 50% of cases, dizziness is due to problems in the vestibular system. But today’s VEMP methods have major shortcomings, and can cause hearing loss and discomfort for patients.

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For example, the VEMP test uses very high sound levels, and may, in fact, cause permanent hearing damage itself, according to the university’s press release.  And, if the patient already suffers from certain types of hearing loss, it may be impossible to draw any conclusions from the test. The Chalmers researchers’ new method offers significant advantages.

“Thanks to this bone conduction technology, the sound levels which patients are exposed to can be minimized,” said postdoctoral researcher Karl-Johan Fredén Jansson, who made all the measurements in the project. “The previous test was like a machine gun going off next to the ear—with this method it will be much more comfortable. The new vibrating device provides a maximum sound level of 75 decibels. The test can be performed at 40 decibels lower than today’s method using air-conducted sounds through headphones. This eliminates any risk that the test itself could cause hearing damage.”

The benefits also include safer testing for children as well as patients with impaired hearing function due to chronic ear infections or congenital malformations in the ear canal and middle ear.

The vibrating device is compatible with standardized equipment for balance diagnostics in healthcare and the cost of the new technology is estimated to be lower than the corresponding equipment used today.

A pilot study has been conducted and recently published. The next step is to conduct a larger patient study in collaboration with Sahlgrenska University Hospital in Gothenburg, where 30 participants with normal hearing will also be included.

More about the research

The scientific article “VEMP using a new low-frequency bone conduction transducer” has recently been published by Dove Medical Press, in the journal Medical Devices: Evidence and Research.

Chalmers’ partners in the study are the Sahlgrenska Academy at the University of Gothenburg, and the Danish audio companies Ortofon andInteracoustics. Grants for this project are received from Vinnova (Swedish Innovations Agency) and Hörselskadades Riksförbund (Hearing Impairment Federation).

See the researchers’ own presentation of the project

Read more about research on medical signals and systems

Original Paper: Håkansson B, Fredén Jansson K-J, Tengstrand T, et al. VEMP using a new low-frequency bone conduction transducer. Medical Devices: Evidence and Research. 2018;11:301-312.

Source: Chalmers University of Technology, Medical Devices: Evidence and Research

Image: Johan Bodell/Chalmers University of Technology