Single-Sided Deafness (SSD)
Single-sided deafness (SSD) is a severe to profound hearing loss in one ear combined with normal or near-normal hearing in the other ear. Unlike moderate unilateral hearing loss, where the poorer ear may still contribute some useful hearing, SSD means the worse ear provides essentially no functional auditory input. The condition can arise from sudden sensorineural hearing loss, vestibular schwannoma surgery, viral inner ear infection, trauma, or be present from birth.
People with SSD experience the loss of all binaural hearing advantages: they cannot determine where sounds are coming from, they lose the binaural squelch effect that normally suppresses background noise, and they experience the head shadow effect, where the head blocks sound from reaching the hearing ear when a speaker is positioned on the deaf side. These challenges are particularly pronounced in noisy environments, group settings, and driving.
Management options include CROS hearing aids (which route sound from the deaf side to the hearing ear), bone-anchored hearing aids (which transmit sound through the skull to the cochlea of the hearing ear), and increasingly, cochlear implantation. Evidence supporting cochlear implantation for SSD has grown considerably, with research showing meaningful improvements in sound localization and speech in noise after implantation of the deaf ear. In Canada, candidacy assessment for each option takes place through audiology and cochlear implant programs.
