Dead regions in the cochlea at high frequencies: implications for the adaptation to hearing aids

In patients with moderate to severe high-frequency hearing loss, cochlear damage may include “dead regions” where there are no functional inner hair cells and/or associated neurons. Aim: This study examines speech recognition in sensorineural impaired hearing patients with and without cochlear dead regions at high frequencies. Methods: a clinical and experimental study was made of thirty patients with sensorineural hearing loss that were classified into two groups: group 1 - included 15 subjects with hearing loss and no dead regions; and group 2 - included 15 subjects with dead regions in the cochlea at high frequencies. Patients undertook word recognition score and speech reception threshold tests, with and without background noise. The speech tests were done with and without hearing aids in two situations: program 1 - broadband amplification (bandwidth 8000 Hz); and program 2 - amplification up to 2560 Hz, without high frequency gain. Results: For subjects with no dead regions in the cochlea (group 1) performance improved with program 1. For subjects with dead regions in the cochlea (group 2) performance improved with program 2. Conclusions: Subjects with no dead regions in the cochlea benefited from high-frequency information. Subjects with dead regions in the cochlea benefited from reduced gain at high frequencies.