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Abstract

To the Editor Dr. Snapp eloquently recognizes many of the problems and difficulties raised with respect to patient expectations in the rehabilitation of single-sided deafness (SSD) using bone-anchored implants (BAIs). She rightly asserts that “clinicians must be clear in identifying what the implant system will be able to accomplish for the patient.” She also observes that “BAIs are merely a means to provide access to sound arriving at the deaf ear” and that “BAIs do not overcome the loss of localization ability for these patients.” Unfortunately, by presenting an article that focuses upon speech-in-noise testing, she risks suggesting that this is a handicap that can be effectively treated with BAIs. Although she has been able to show a significant reduction in signal-to-noise ratio loss using the BAI, it is important to recognize the artificiality of the test used and the particularly favorable protocol chosen. In this context, the QuickSIN test is more a test of the lifting of the head-shadow than of speech comprehension in noise characterized by binaural squelch and sophisticated interhemispheric “top-down” auditory processing. By presenting noise to the hearing ear and speech to the implanted ear, the researchers have demonstrated the aided benefit seen in other studies (1–4) without seeing the aided handicap imposed by the BAI if noise—rather than signal—is presented to the implanted ear. This handicap—the introduction of unwanted and distracting noise—emphasizes that the BAI is a “means to provide access to sound arriving at the deaf ear” whether that be “good” sound or “bad.” There can be no doubt that a significant number of patients with SSD derive benefit from BAIs and the relief from the head-shadow they offer. This benefit, however, is not due to improved speech-in-noise comprehension as it is perceived by binaurally hearing individuals, as it is not due to improved sound localization: such benefits are only seen when a physiological and anatomically bilateral auditory pathway is reestablished, as is possible in a proportion of patients with SSD. Initial studies of cochlear implantation (CI) suggest that this may be feasible (5–7). The study by Arndt et al. (6)—the first to compare BAI and CI for this indication—reports improved subjective and objective outcomes with CI and does not find any negative impact arising from noise being presented to the aided ear. Experience of cochlear implantation in SSD is promising but limited, and further research is required. We would advocate a protocol using auditory scene analysis (8), which considers the ways that auditory objects are identified and perceived in the environment to investigate any benefits of true binaural hearing in rehabilitated SSD patients. If cochlear implantation proves effective in this regard, it might be time to move away from the partial solutions offered by BAIs toward a more radical form of rehabilitation in those selected cases who feel sufficiently handicapped by SSD. Thomas Peter Cutlack Martin, FRCS (ORL-HNS) Skull Base Fellow ENT Department Addenbrooke’s Hospital Hill’s Road Cambridge, U.K. David Baguley, Ph.D. Audiology Department Addenbrooke’s Hospital Hill’s Road Cambridge, U.K.