8The Very Young Infant

FWhy earlier is better: the developmental rationale

The central auditory pathway has a sensitive period of maximal plasticity in the first few years of life, and cortical auditory maturation is best when stimulation begins before about three and a half years of age. Children implanted in infancy more often reach age-appropriate spoken language, and a large proportion of those implanted before twelve months track with normal-hearing peers. Earlier implantation shortens the period of auditory deprivation, so the brain wires to electrical sound while it is most receptive rather than after deprivation has begun to reorganise the cortex. Universal newborn hearing screening makes early diagnosis possible, which is the prerequisite for taking advantage of the plastic window. The principle that drives the field downward in age is that time without sound is the enemy of spoken-language outcome.[2002][2016][2010]

TThe 2020 lowering of the age to nine months

In March 2020 the FDA approved cochlear implantation from nine months of age for children with bilateral profound sensorineural hearing loss, down from the prior twelve-month threshold. The approved age has fallen in steps over three decades, from two years, to eighteen months, to twelve months, and now to nine months as evidence and technology matured. Off-label implantation below the approved age was already practised at experienced centres in selected children before the threshold formally moved. Lowering the age widens the window of greatest plasticity that the implant can exploit but raises the bar for diagnostic certainty and surgical safety in ever-younger infants. The change applies to defined device systems and to children who show limited benefit from a trial of appropriately fitted binaural hearing aids.[2020][2016]

CPractical challenges in an infant

Confirming profound loss in a non-verbal infant relies on the objective battery rather than behavioural audiometry, and a documented hearing-aid trial is needed to demonstrate insufficient benefit before surgery. The infant skull is thin and the mastoid small, so surgeons modify fixation, minimise bone removal and keep the incision small to fit the developing temporal bone. General anaesthesia in an infant demands an experienced paediatric anaesthetist and full paediatric perioperative facilities to manage the smaller blood volume and airway. Pneumococcal and other vaccinations recommended for implant recipients should be planned around the surgery to reduce the lifelong risk of meningitis. The combination of diagnostic, surgical and anaesthetic demands is why infant implantation is concentrated in high-volume programmes.[2016][2021][2020]

CSafety evidence and bilateral simultaneous implantation

Pooled data show major complication rates around three percent and minor complications a few percent in infants, comparable to older children and to adults. Surgical, anaesthetic and device-related complication rates do not differ significantly between infants under nine or under twelve months and older children in large comparative series. No anaesthetic deaths and no excess of anaesthetic complications have been a consistent finding when infant implantation is done in appropriately resourced centres. Bilateral simultaneous implantation in infancy gives two ears at once during the plastic window without adding meaningful surgical time or hospital stay over a single device. The safety record is what justifies extending candidacy downward, provided the infrastructure for paediatric care is in place.[2021][2021][2016]