Hidden hearing loss (HHL) refers to the normal hearing threshold in the conventional pure tone hearing test, but there is a certain degree of suprathreshold auditory perception defects, such as: speech resolution in noisy environment is reduced.
As early as 1989, a large-scale survey and research in the UK showed that 26% of adults have greater difficulty in speech hearing in noisy environment, but only 16% of them have increased their hearing sensitivity (the average hearing threshold of standard pure tone hearing test 0.5-4khz ≥ 25 dB HL).
At present, the pathogenesis of recessive hearing loss is not completely clear. In the past, HHL was often thought to be related to the processing disorder of auditory center. However, many studies in recent years have suggested that the damage of peripheral auditory organs may also be an important reason. More and more attention has been paid to the damage of synapses between hair cells and type I afferent auditory nerve fibers.
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So, how to diagnose the recessive hearing loss?
In HHL, the cochlear synapses have not changed the hearing threshold, which can not be detected by conventional audiology.
Professor Bernstein of the University of Connecticut has proposed a new method for HHL diagnosis. They found that despite the normal results of routine hearing tests in patients with this type of recessive hearing loss, significant binaural hearing processing disorders may exist.
As we know, binaural hearing plays an important role in people’s sound source location, noise environment listening and multi-person conversation. Therefore, this test can simulate various scenes in daily life, set different loudness, and observe the effect of binaural listening.
In order to verify the validity of the test, they carried out the following experiments:
Introduction to the experiment
Objective To observe whether patients with “slight” or “recessive” hearing loss have binaural hearing impairment;
Methods: 31 healthy subjects were selected for binaural auditory awareness test;
Results → when the time difference between the two ears is larger, the higher the binaural perception threshold of 500 Hz and 4kHz points is, indicating that there is an obstacle in the process of inter ear attenuation; when the 4kHz threshold of a subject is ≥ 7.5db HL, the binaural perception threshold is increased; when there is no binaural signal, the binaural perception threshold is not increased.
Other → head
1) the increase of binaural perceptual threshold is more related to auditory threshold than to age; 2) the increase of binaural perceptual threshold may also be related to the decrease of binaural noise reduction.
At present, ABR, FFR and cochlear electrogram are the main methods to detect recessive hearing loss. Professor Bernstein’s new method undoubtedly provides a new idea. But generally speaking, recessive hearing loss is still in the stage of scientific research and exploration. In the future, we need to further clarify its mechanism, research and develop clinical detection technology related to its diagnosis and diagnosis.
Link：Is there a new method for the diagnosis of recessive hearing loss?
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