ABSTRACT
Objective: To observe the morphological changes on cochlear hair cells of rats in simulated weightlessness and inboard noise and to investigate the different changes in three turns of hair cells.Methods: Thirty-two healthy SD rats, all males, were randomly divided into four groups: control group, weightlessness group, noise group and weightlessness+noise groups (n=8).Then rats were exposed to-30° head down tilt as simulated weightlessness and inboard noise including steady-state noise which was (72±2) dB SPL and impulse noise up to 160 dB SPL in spaceship environment.The control group was kept in normal condition for 8 weeks.Bilateral auditory brainstem response (ABR) thresholds were tested before and after exposure respectively, and immunofluorescence staining and scanning electron microscopy (SEMs) of basilar membrane were applied after exposure.Results: ABR threshold shifts of each group were higher after exposure.There was difference between ABRs of the experiment groups before and after exposure (Pnoise group>weightlessness group>control group and the damage degree of the four turns of hair cells: basal turn>mid turn>top turn.Conclusion: The rats exposed to the above environment for 2 weeks displayed obvious changes in cochlea morphology, and the weightlessness+noise group had the most obvious damage.
ABSTRACT
Objective To investigate residual hearing of children with sensorineural hearing loss in whom wave V was not found in ABR testing and to emphasize the importance of behavioral audiometry in determining the residual hearing.Methods Residual hearing obtained by behavioral audiometry of 101 children with SNHL was studied in relation to the absence of wave V in both click-ABR and tone burst-ABR tests.Results All children have residual hearing of different degrees at different frequencies.There appeared to be a higher percentage of lowfrequency residual hearing than middle and high frequencies.Also,the residual hearing at low frequencies appeared to be better than those in the middle and high frequencies.Average residual hearing thresholds in the right ears from 500 to 4 000 Hz were 106.81±7.13,110.00±7.90,111.78±5.22,112.06±7.08 dB HL and those in the left ears were 98.01±3.98,111.30±7.18,112.06±7.08,108.33±7.23 dB HL.Conclusion The absence of wave V in ABR does not mean total deafness.For those children with no wave V in ABR,behavioral audiometry must be conducted to determine children's behavioral hearing thresholds in order to know their residual hearing.