7Nothing on the Outside: The Totally Implantable Implant

FWhat 'totally implantable' actually means

A totally implantable cochlear implant (TICI) buries every functional block under the skin: microphone, sound processor, battery and electrode array, with nothing worn externally. This is distinct from today's devices, which are partly implanted (receiver-stimulator and array internal) but depend on an external behind-the-ear or off-the-ear processor plus a transcutaneous coil. An intermediate step is the 'invisible-but-chargeable' design: internal mic, processor and battery for everyday use, with an external coil worn only to recharge the implant and to upload new settings. The TIKI research device demonstrated this directly with two modes - an external hearing mode using a conventional processor, and an invisible hearing mode running entirely on the internal microphone and battery.[2008][2017]

CWhy patients want it: always-on hearing without the device

Always-on hearing means sound during the moments current users miss most - waking, sleeping, swimming, showering and the seconds before the processor is put on in the morning. Removing the external piece removes a visible marker of deafness; reduced stigma is a recurring reason candidates and families give for wanting an invisible device. No external hardware means no daily on/off routine, no parts to lose or damage, and no water/dust vulnerability at the worn site - relevant for young children and active adults. In the TICI feasibility study, recipients chose to use invisible-hearing mode for a median of about half their listening time (range 22-88%), showing real-world appetite for processor-free hearing even when an external option was available.[2025][2008]

TThe three hard problems

Problem one - the microphone: a sensor under the skin is damped by overlying tissue and picks up chewing, footfall and the user's own voice, degrading the sound it captures (covered in detail in the next module). Problem two - power: an implanted battery must run continuously yet be small, sealed, and rechargeable for years; transcutaneous charging and very-low-power electronics are the practical near-term answer, with energy harvesting still preclinical. Problem three - serviceability and upgradability: sealing everything inside means software, microphone and battery cannot be swapped at a clinic visit the way an external processor can, so the implant must outlast many processor generations or be re-operable. These three couple together - a noisier internal mic needs more processing, which costs more power, which strains the sealed battery - so a TICI is an integrated trade-off rather than three independent gadgets.[2018][2017][2012]

CWhere it stands today

TICI remains investigational: first-in-human work and a recent ten-adult feasibility study show it can work, but no totally implantable CI is in routine clinical use. The recent feasibility study also exposed the reliability gap - two of ten devices failed from a microphone-related hermeticity (sealing) problem, the kind of failure that is trivial with an external mic and serious with an internal one. Clinic-now reality: every commercial implant still uses an external processor; the honest counselling message is that invisible hearing is a credible research direction, not a product a patient can be offered today. The likely path is incremental - invisible-but-chargeable hybrids first, full independence later - rather than a single leap to a sealed, never-serviced device.[2025][2017]