2015 Volume 141 Pages 4-5
The bone-anchored hearing aid (BAHA) has been used since 1977, and is currently approved for a variety of bilateral hearing loss categories including conductive hearing loss, and mixed hearing loss. The BAHA is also approved for patients with unilateral hearing loss, and this entity occupies one-third of the total number of cases.
In Japan, however, the BAHA has not been approved for patients with unilateral conductive hearing loss and single sided deafness (SSD), because no significant effect could be confirmed based on the results of a prior multi-center clinical study.
In the present study, we re-evaluated the effectiveness of BAHA for the patients with unilateral conductive hearing loss and SSD by adding new test conditions of a speech recognition test in noise and the sound localization test to those tests which were used in the multi-center clinical study.
The results of the speech recognition test in the patient with SSD showed a decrease of 16% in the score with BAHA in noise (+10 dB signal-to-noise ratio) compared in cases without BAHA, when noise was presented on the side of the patient’s poor ear and speech was presented on the side of better ear. On the other hand, in patients with unilateral conductive hearing loss, the score with BAHA increased 2% compared in cases without BAHA.
As to the result of the sound localization test, in the patient with SSD, the mean absolute error (MAE) was 45° with BAHA and 52.5° without BAHA. On the other hand, in the patient with unilateral conductive hearing loss, the MAE was 26.1° with BAHA and 36.9° without BAHA.
In other words, the effectiveness was reversed for each of the pathological conditions in the present study. We think that these results are derived from the difference of the subject’s having only one functioning inner ear in SSD but having bilateral functioning inner ears in unilateral conductive hearing loss. Therefore, the effectiveness of BAHA should be evaluated separately in patients with unilateral conductive hearing loss and SSD even in cases showing similar hearing disturbance.
