19Bilateral & bimodal candidacy

TThe binaural window

Two ears give localisation and speech in noise by letting the brain compare the two sides (Chapter 3). But the capacity to do so must be developed and maintained: prolonged monaural stimulation actively inhibits the deprived contralateral pathway. So where bilateral candidacy exists, the worse or longer-deaf side should still be implanted to preserve binaural potential — the opposite of writing it off.

CSimultaneous or short delay

Timing is part of bilateral candidacy. Two implants should be simultaneous or placed with a short (under ~2-year) inter-implant delay; longer gaps risk losing the binaural window, especially in children, where a long delay can let an aural preference for the first ear set in. The decision to pursue the second ear is therefore also a decision about when.

CRedundancy and task-dependent benefit

A second implant carries an argument independent of binaural hearing: redundancy against device failure, so a technical fault never plunges the patient back into total deafness. The binaural benefit itself is real but task-dependent — easy tests in quiet miss it, while harder, more realistic speech-in-noise and localisation tasks reveal the advantage.[2007] Listening effort and fatigueare emerging candidacy variables too: many users “get by” but are exhausted by day's end, and effort measures may one day help decide when to add the second ear.

CSecond implant vs bimodal

When the non-implanted ear keeps useful acoustic hearing, the choice is between a second implant and a bimodal fit (implant plus contralateral hearing aid). The trade-off is clear: a second implant favours binaural development and redundancy; bimodal preserves and exploits residual low-frequency acoustic hearing that the implant conveys poorly, often giving fuller, more natural sound. The right answer is individual — and, like everything in this chapter, it flows from the candidacy assessment into the operative plan that follows.