EXPERIMENTAL STADIES ON THE ACOUSTIC REFLEX OF THE INTRA-AURAL MUSCLES AND ITS CLINICAL APPLICATION

Abstract

In order to establish an objective audiometry, the anther studied the intra-aural muscle reflex elicited by sound stimulation.
The changes of acoustic impedance at eardrum i.e. effective volume change and air pressure change of the external ear canal caused by middle ear muscle reflex were measured by using modified Nagashima's *Aural Reflex Indicator* and electric micro-manometer, respectively.
Measurements were performed on 60 normal subjects and the patients with peripheral facial nerve palsy (30), Eustachian tube stenosis (60) and noise induued deafness (40). In animal experiments, 30 rabbits and 40 guinea pigs were used. The following conclusion can be drawn from the results.
1) The effect of the acoustic middle ear mus- cle reflex was recorded by electric micro-manometer in 97% of the normal ears, while by Aural Reflex Indicator it was detected in 85%.
2) White noise is found to be most effective for eliciting the aural reflex in humann as well as experimental animals.
3) The aural reflex effect is almost undetect- able, is any, by Aural Reflex Indicator in cases of conductive type deafness and facial nerve palsy, but it is recorded remarkably by electric micro- manometer.
4) The individual susceptibility to noise ind- uced deafness could be presumed from the magni- tude of reflex activity.
5) The experimental study and the study in the patients with facial nerve palsy made it pos- sible to distinguish the reflex effect of the tensor tympany muscle and stapedial muscle.