Prospective study of sound localization in patients with single sided deafness and asymmetric hearing loss treated with cochlear implant

Background and Objective: Sound localization plays a crucial role in our daily lives, enabling us to recognize voices, respond to alarming situations, avoid dangers, and navigate towards specific signals. However, this ability is compromised in patients with Single-Sided Deafness (SSD) and Asymmetric Hearing Loss (AHL), negatively impacting their daily functioning. The main objective of the study was to quantify the degree of sound source localization in patients with single-sided deafness or asymmetric hearing loss using a Cochlear Implant (CI) and to compare between the two subgroups. Materials and Methods: This was a prospective, longitudinal, observational, single-center study involving adult patients diagnosed with profound unilateral or asymmetric sensorineural hearing loss who underwent cochlear implantation. Sound localization was assessed in a chamber equipped with seven speakers evenly distributed from-90(degrees )to 90(degrees). Stimuli were presented at 1,000 Hz and intensities of 65dB, 70dB, and 75dB. Each stimulus was presented only once per speaker, totaling 21 presentations. The number of correct responses at different intensities was recorded, and angular error in degrees was calculated to determine the mean angular distance between the patient-indicated speaker and the speaker presenting the stimulus. Both assessments were conducted preoperatively without a cochlear implant and two years post-implantation. Results: The total sample comprised 20 patients, with 9 assigned to the SSD group and 11 to the AHL group. The Preoperative Pure Tone Average (PTA) in free field was 31.7dB in the SSD group and 41.8dB in the AHL group. There was a statistically significant improvement in sound localization ability and angular error with the use of the cochlear implant at all intensities in both SSD and AHL subgroups. Conclusions: Cochlear implantation in patients with SSD and AHL enhances sound localization, reducing mean angular error and increasing the number of correct sound localization responses.