[Evoked oto-acoustic emissions in retrocochlear deafness].
In order to give a contribution to the genesis of the EOAEs, we have recorded the echoes in 6 subjects affected with unilateral acoustic neuroma, surgically proven (I. group); 11 subjects with sensorineural hearing loss with electrophysiological or balance signs of retrocochlear impairment (II. group) and 10 normally hearing young subjects as control group. In this study EOAEs have been recorded in response respectively to 3 ms 1000 Hz tone-burst and to 200-5000 filtered click, both sending with 2048 stimuli, at a repetition rate of 21 pps and different stimulus intensities ranging from 40 db SPL to saturation threshold in 10 db steps. The results have shown that the EOAEs were present in half of the tested patients in response to the clicks in both I. and II. group and in all the ears to the tone-burst although the 1.0 KHz audiometric threshold mean were > 65 db HL in I. group and in a third of the subjects in the II. group. The properties of EOAEs (detection and saturation threshold, dynamic range and duration) depended on the degree of hearing loss. These results suggest that acoustic tumor could determine a wallerian degeneration of the external fibers of the VIII nerve and consequently a dysfunction of the correspondent external hair cells of the cochlea, while in the II. group a contemporary or secondary involvement of the cochlear structures is possible.
Salonna
I
I
Centro di Audiologia e Otologia, Università di Bari.
Bartoli
R
R
Quaranta
A
A
D000328:Adult; D001933:Brain Stem / Q000503:physiopathology; D003638:Deafness / Q000503:physiopathology*; D006198:Hair Cells, Auditory / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000503:physiopathology*; D017084:Otoacoustic Emissions, Spontaneous; D000159:Vestibulocochlear Nerve / Q000503:physiopathology; D014855:Wallerian Degeneration
Otoemissioni acustiche evocate nelle sordità retrococleari.