13The expanding indications
The clearest sign of how far implantation has come is the list of people who now qualify and once did not. The old criteria demanded essentially total deafness; today candidacy reaches patients with real residual hearing, those whose good low-frequency hearing can be preserved and combined with electric stimulation in the same ear, people with a single dead ear beside a normal one, and those whose deafness is a disorder of neural timing rather than of the cochlea. Each of these expansions rests on the same logic that ran through the previous chapter: wherever a hearing aid cannot deliver enough, the implant becomes the better option — and the evidence for benefit in these groups keeps accumulating. This module surveys the expanding frontier of candidacy.
TA moving frontier
Candidacy is not a fixed list but a moving frontier. As outcomes improved, the categories of patient who benefit widened well beyond the totally deaf adult. The unifying principle is simple and familiar: offer the implant wherever amplification falls short, even if the ear is not silent.[2021]
CResidual hearing & electric-acoustic
Useful residual hearing no longer disqualifies a candidate — the criterion is functional benefit, and patients may keep substantial aided understanding and still qualify. A special case is good low-frequency hearing with steeply-falling highs: electric-acoustic (hybrid) stimulation preserves the natural low-frequency acoustic hearing and adds electric high frequencies in the same ear, combining the best of both — provided surgery preserves the residual hearing.[2004]
CSingle-sided & asymmetric
Single-sided deafness — one dead ear beside a normal one — is now an accepted indication: the implant restores true input to the deaf side, can quieten the tinnitus that often accompanies it, and gives back some binaural hearing that a CROS aid cannot. Asymmetric losses, where a much poorer ear sits alongside an aidable better ear, are handled similarly — implant the poor ear, often used bimodally with an aid on the better side.
CAuditory neuropathy
Auditory neuropathy is the category where the lesion is one of neural timing, not of the cochlea — so amplification often fails while the implant, imposing synchronous firing, frequently succeeds (Chapter 9). Its inclusion in candidacy is a vivid reminder that the decision depends on where the lesion sits, not the audiogram alone. Across all these groups the message is the same: a patient outside the old criteria may be an excellent candidate today.
TCDefining SSD, AHL — and the mandatory trial
The new indications have precise definitions and their own pathway. Single-sided deafness is profound loss in one ear with the other near-normal (PTA up to ~40 dB); asymmetric hearing loss is an inter-ear difference of at least ~30 dB with a poor ear. Both are treated as distinct indications, not folded into bilateral candidacy, and both require a minimum two-week trial of CROS or Baha first, so the patient experiences the limits of signal-rerouting before an implant is offered. For SSD the implant beats those devices for speech in noise and localisation, and intractable tinnitus in the deaf ear is a legitimate driver in its own right.[2011]
Auditory neuropathy deserves a precise diagnosis before implantation. OTOF (otoferlin) mutations cause about half of cases and are a presynaptic lesion the implant bypasses — making those children excellent candidates, even though they classically pass newborn OAE screening yet show profound deafness on ABR. Where doubt remains, the eABR (normal versus abnormal) helps predict the implant outcome.[2007]
Is this patient a candidate, and why?
Which of these is now an accepted expanded indication for cochlear implantation?
What is electric-acoustic (hybrid) stimulation, and whom does it suit?