Interaction Between Electric and Acoustic Stimulation Influences Speech Perception in Ipsilateral EAS Users.

Area of Science:

• Audiology
• Neuroscience
• Biomedical Engineering

Background:

• Cochlear implants (CIs) can be combined with acoustic stimulation for users with residual hearing.
• Electric-acoustic masking can occur when electric and acoustic stimulation overlap, potentially impacting speech understanding.
• Optimizing CI fitting strategies is crucial for maximizing speech reception in users with residual hearing.

Purpose of the Study:

• To determine electric-acoustic masking in cochlear implant users with residual hearing.
• To investigate the influence of different fitting strategies on speech reception.
• To compare standard fitting strategies (meet, overlap) with a novel masking-adjusted fitting (UNMASKfit).

Main Methods:

• Fifteen experienced MED-EL Flex electrode CI users with ipsilateral residual hearing participated.
• A crossover design compared three fitting strategies: meet, overlap, and UNMASKfit.
• Psychoacoustic masking measured acoustic threshold changes; speech reception in noise used the Oldenburg Matrix Sentence test.

Main Results:

• Electric-acoustic masking elevated acoustic thresholds, particularly with a one-octave frequency separation.
• Speech reception was significantly reduced with the overlap fitting strategy, especially in individuals with strong masking.
• The UNMASKfit strategy showed a trend toward greater benefit and improved speech reception compared to electric stimulation alone.

Conclusions:

• Electric-acoustic stimulation interacts, and overlap fitting can impair speech reception in noise.
• The UNMASKfit strategy offers enhanced acoustic benefit and reduced electric stimulation, potentially preserving hair cell function.
• UNMASKfit may improve speech reception by enabling better use of residual hearing and could be beneficial for initial CI fittings.