4.2 Key findings and clinical applicability
To find whether hearing thresholds influence hearing-aid use, we
compared them with hearing-aid use for PTA4 for each AHL
subtype. Only one hearing threshold at 1 kHz in the better ear was
significantly lower for those who continued hearing-aid use. This is not
a commonsense result, but it is interesting. These findings could be
explained by the active role of the ipsilateral minor pathway in the
central auditory nervous system (CANS).13, 14 The main
pathway of a healthy ear goes to the contralateral CANS, but there is a
minor pathway to the ipsilateral CANS, which means that an intact
auditory pathway in a healthy ear can guarantee binaural interaction
when AHL is treated monaurally in the worse ear.15, 16A second explanation comes from the main role of a patient’s better ear
in hearing and listening. In many patients with AHL who are fitted
monaurally in the worse ear, aided hearing in the worse ear remains
supplementary, especially in situations in which the sound of interest
is soft and arrives from the side of the worse ear. Sound localization
is needed to locate the person speaking in a group conversation or where
there are multiple talkers or noise. The better ear still plays the main
and crucial role when the sound of interest arrives from the front or
the side of better ear, sound localization is needed to locate only one
talker, or a single talker is speaking in a noisy
place.17
We found only one audiometric parameter (a hearing threshold at 1 Hz for
the better ear) that affected the outcome of hearing-aid use for AHL
patients with an aid in the worse ear, like previous
studies.6 This demonstrated the importance of hearing
in the better ear when AHL is amplified monaurally in the worse ear.
This result accords with previous reports stating that preserving the
ear with the better auditory threshold significantly improves the
intelligibility of speech-in-noise.18