Uncover the mystery of the dead zone of the cochlea

I believe that many audiologists have encountered this situation in the process of debugging the hearing aids for patients. From the audiogram, the hearing loss is within the range of hearing aids, but after wearing the hearing aids, the patient’s speech recognition rate is not good, even Increase gain and worse speech resolution. This phenomenon suggests that the patient may have a cochlear dead zone.

1What is the cochlear dead zone?

Cochlear dead zonecochlear dead
) refers to the inner hair cells in the cochlea/Or an area where the auditory nerve function is severely impaired and does not function properly. Therefore, information generated by vibration of the basement membrane in these areas cannot be transmitted to the central nervous system.

Cochlear dead zone

2What causes the cochlear dead zone?

The dead zone of the cochlea may be due to various factors such as microcirculatory disorder of the inner ear, causing blood supply disorders in the spiral ganglion and cochlear inner hair cells, leading to pathological changes such as loss of cochlear neurons and spiral ganglion cell degeneration. The possible cause, drug-induced sputum patients have the highest detection rate of the cochlear dead zone, followed by noise convulsions and sudden convulsions.

Cochlear dead zone

3What kind of patients will have a cochlear dead zone?

Related data shows: hearing loss> 70dBPrevalence of cochlear dead zone in patients >50%.58.3%The patient with sensorineural hearing loss has a cochlear dead zone;

Children and adults with acquired hearing impairment or congenital hearing impairment may have a cochlear dead zone;

The dead zone of the cochlea has nothing to do with the gender and age of the patient, and is related to the degree of hearing loss and the course of the disease. The more severe the hearing loss, the longer the course of the disease, the higher the detection rate of the cochlear dead zone.

Cochlear dead zone

4What are the hazards in the cochlear dead zone?

The cochlear dead zone affects the patient’s speech recognition rate, and it is more difficult to distinguish speech speech than in a cochlear-free dead zone, whether in a quiet or noisy environment.

If a hearing aid is used in a patient with a cochlear dead zone, if the gain is increased in the dead zone, it will not improve the clarity of the speech perception of the hearing loss, but will reduce the speech resolving ability.

Therefore, the detection of the dead zone of the cochlea is very important, which helps the audiologist to better debug the hearing aid for the hearing loss patient.

Cochlear dead zone

5How to detect the dead zone of the cochlea?

Professor of Auditory Perception, Department of Experimental Psychology, University of Cambridge, UK Brian CJ MooreWait for2000Equilibrium noise threshold testHaveTest), this method is fairly easy and convenient for clinical audiologists to use and assess whether the cochlear dead zone is present.


First, pure tone hearing threshold detection (measure pure tone hearing threshold), channel1Give pure tone, channel2Giving masking noise;

Mixing the two-channel sound into the test ear to perform the same side masking (the masking noise intensity is on the same side pure tone hearing threshold)10dBThe masking noise intensity at this time isHavestrength);

aisle1Control the test pure tone and then test the hearing threshold under the mask;

The pure tone threshold that the test ear can hear isHaveThreshold value

Test one frequency and then test the other frequency in the same way until the end of the test after all frequency points have been tested;

Test frequency:


1 When the hearing loss of a certain frequency is less than or equal to ≤60dB时,HaveStrength is set to70dB. For most patients this intensity produces reliable results without causing discomfort;

2 when a certain frequency of hearing loss ≥60dB时,HaveThe intensity is set to the pure tone threshold of the frequency+10dB;

3 ifHaveThe strength is too uncomfortable or has reached the maximum strength90dBHL.HaveThe intensity can be set equal to the pure tone hearing threshold;

HaveBroadband noise

HaveStep size of the test:2dB.HaveThreshold test andHaveThe rising step of strength is2dB.

effectiveHaveStrength: makeHaveThreshold increase to pure tone threshold10dBAboveHaveThe strength is in line with the test.

Judgment of the cochlear dead zone:HaveThreshold ratioHavehigh strength10dBAnd above.

Cochlear dead zone

6How to deal with patients with dead zone in the cochlea?

For patients with low-frequency cochlear dead zone, reduce the low-frequency gain, so that it can make full use of the medium-high frequency speech information, without causing low-frequency upward masking;

For patients with high frequency cochlear dead zone, increase the low frequency gain while reducing the high frequency gain. It is recommended to use a hearing aid with a frequency shifting function, and the condition allows the implanted cochlear implant.

Link:Uncover the mystery of the dead zone of the cochlea

REF: Hearing AidsHearing amplifierBTE Hearing Aids
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