Hidden hearing loss (HHL) means that the normal pure tone hearing test shows that the hearing threshold is normal, but there is a certain degree of threshold upper auditory perception defects, such as: decreased speech resolving ability in noisy environment.
In the UK, as early as 1989, a large-scale survey showed that 26% of adults have difficulty in speech hearing in noisy environments, but only 16% of them have improved hearing sensitivity (standard pure-tone hearing test 0.5) ~4k Hz average hearing threshold ≥ 25 dB HL).
The pathological mechanism of recessive hearing loss is not fully understood. It has been thought that HHL may be related to auditory central processing disorders, but many studies in recent years suggest that peripheral auditory organ damage may also be an important cause. Among them, the synaptic damage between the inner hair cells of the cochlea and the type I afferent auditory nerve fibers has received more and more attention.
So, how is the hidden hearing loss diagnosed?
HHL cochlear synaptic lesions have not caused changes in hearing threshold, and this invisible auditory function defect cannot be detected by conventional audiological examination.
The latest study by Professor Bernstein of the University of Connecticut in the United States has proposed a new method for the diagnosis of HHL. They found that although the results of routine hearing tests in such patients with recessive hearing loss were normal, there may be significant binaural hearing impairment.
And we know that binaural hearing plays an important role in scenes such as sound source localization, noise environment listening and multi-person dialogue. Therefore, the test sets different loudness by simulating various scenes in daily life, and observes the effect of binaural listening.
To verify the validity of the test, they conducted the following experiments:
Introduction to the experiment
Objective → To observe whether there are binaural hearing disorders in patients with “slight” or “recessive” hearing loss;
Method→Select 31 name hearing subject for binaural hearing detection test;
RESULTS → The greater the time difference between the arrival of the signals in the ears, the higher the binaural awareness threshold at the two frequency points of 500 Hz and 4k Hz, indicating that the aural attenuation treatment is impeded; when a subject’s 4k Hz hearing threshold ≥ 7.5 dB HL At the same time, the binaural threshold is improved; when there is no binaural signal, the binaural threshold is not improved.
Other → head
1) Both ears detect threshold elevation is more related to the hearing threshold and has little to do with age; 2) binaural threshold enhancement may also be associated with reduced binaural noise reduction.
At present, the detection methods of recessive hearing loss are mainly based on objective methods such as ABR, FFR and cochlear electrogram. Professor Bernstein’s new method undoubtedly provides new ideas. However, in general, recessive hearing loss is still in the stage of scientific research and exploration. In the future, it is necessary to further clarify its mechanism, develop relevant clinical testing techniques for diagnosis and diagnosis, and so on.
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