Low Level Stimulation in the Differentiation of Middle Ear Pathology

Abstract

A 20-db SL tone was presented at 4000, 1000 and 500 cps respectively for three minutes. Following each exposure, subjects traced threshold recovery to the stimulating tone for five minutes on a Békésy-type automatic audiometer. Forty-six subjects with aural conductive disorders and 23 subjects with normal hearing were evaluated.

On the basis of this investigation the following conclusions were considered tenable:

1. Epstein and Bower's data suggesting greater Temporary Threshold Shift (TTS) over time for conductively involved ears than for normally-hearing ears were confirmed.

2. Four-thousand cps produced the greatest TTS and provided the most differentiation between normal and conductive ears particularly by the fifth minute of recovery.

3. The amount of TTS was positively correlated with both extent of hearing loss and duration of hearing loss regardless of the specific etiology.

4. Although the Initial Temporary Threshold Shift differentiated normal ears from conductively involved ears, the measure provides uncertainty for clinical diagnosis due to the considerable overlap between the groups.

5. The use of TTS for clinical, audiometric identification of conductive hearing loss appears feasible.

6. The measure of variability change was not as clear-cut as TTS in differentiating conductive from normally-hearing subjects.