Researchers have developed a new test for dizziness that poses less risk for hearing damage, as compared with the commonly used clinical test. Using bone conduction technology, Professor Bo Håkansson and colleagues at the Chalmers University of Technology in Sweden, created a behind-the-ear testing device that is safer and more efficient, especially for patients who already have hearing problems.
Today, balance-related problems are typically diagnosed using vestibular-evoked myogenic potentials (VEMPs) test. However, this test uses high sound levels that may damage hearing. In fact, VEMPs have been associated with a high risk for noise-induced hearing loss, a concern that captured the attention of study lead, Professor Håkansson.
"I knew about the challenges with VEMP using air-conducted (AC) sound and when I understood from early publications that bone conduction (BC) may have some advantages, I became interested," said Håkansson.
When asked about what inspired this idea, he shared: "I have been working with bone conduction applications since the 1980 ties. I have developed the BAHA (my Ph.D. project) and bone conduction implant concepts as well as the B81 for audiometric testing, so I am always open to new ideas for our technology. When I understood that B71 and that the Minishaker B&K 4810 had some other challenges, I came to the idea to modify the B81 to better adapt to BC-VEMP testing at 250 Hz, which had not been used before (my idea to use 250 Hz is based on both technical and physiological aspects."
This novel device is placed behind a patient's ear, where it transforms sound waves into vibrations through the skull, thereby inciting the cochlea inside the ear.
"The first prototype tested on our selves was surprisingly positive, so I applied for a bigger research grant that was approved. This first study is now published in Dove with very positive results," Håkansson noted.
Details of the prototype are discussed in the group's recently published study, "VEMP Using a New Low-Frequency Bone Conduction Transducer."
Compared with the standard VEMP tests, this device promises significant advantages for clinical assessment as well as patient safety.
"If we compare with AC stimuli, this method using BC at 250 Hz seems to be more efficient and require significantly less sound load, making it possible to measure VEMP in patients who have a conduction hearing loss," Håkansson said.
He explained that a missing VEMP response using air conduction can be due to either vestibular nerve issues or hearing loss, which in the latter case would make it practically impossible to measure VEMP.
"If you compare with previously used BC stimuli using the B71/81, they are not strong enough to produce reliable VEMP responses below 500 Hz. The option to the Minishaker, which is very clumsy and must be applied handheld (a vibration device developed form general structural dynamic testing), is not as strong as our new B250 at 250 Hz simply because of its wideband design. The B250 can be much smaller (actually 30 times smaller than the Minishaker) as it is based on a resonance design optimized for 250 Hz," he explained further.
So, what's the next step before this technology becomes available to clinicians?
"We are soon to start clinical studies using the B250 on a wider group of subjects, both on normal subjects, to gain normative data and patients with different vestibular disorders in order to determine the sensitivity and specificity of this method using the B250," said Håkansson.
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