Speech discrimination and binaural processing in bilateral symmetric vs. asymmetric sensorineural hearing loss

To investigate the effects of symmetric and asymmetric sensorineural hearing loss (SSNHL and ASNHL) on speech discrimination abilities and binaural processing, including integration and interaction.

This cross-sectional study included 36 adult patients with bilateral sensorineural hearing loss, divided into two groups based on the symmetry of their hearing loss: ASNHL and SSNHL. Speech discrimination abilities were evaluated using the maximum speech discrimination score (SDSmax) with Arabic monosyllabic words. Binaural integration was assessed using the free-recall double dichotic digit test (DDT), while binaural interaction was evaluated through the binaural fusion test (BFT).

The SDSmax of the worse-hearing ear in ASNHL patients (48.89 ± 10.13%) was significantly lower than in SSNHL patients (69.33 ± 7.97%) with comparable degrees of hearing loss. ASNHL patients exhibited a greater disparity between the better and worse-hearing ears in DDT scores (53.15 ± 13.98%) compared to SSNHL patients (22.96 ± 5.93%). Additionally, the BFT scores in ASNHL patients (55.14 ± 13.30%) were significantly lower than in SSNHL patients (72.92 ± 12.55%).

ASNHL patients experience greater impairments in speech discrimination, binaural integration, and interaction compared to SSNHL patients. These differences likely stem from auditory deprivation and asymmetry-induced deficits. Developing tailored hearing rehabilitation strategies is critical to addressing the unique challenges posed by asymmetric hearing loss.