A child can fail the newborn screen because of "junk" still in their ears at birth. They are then retested with the screening tool, and if they fail again, they are given the ABR. The ABR diagnoses the hearing loss. It tell you how much loss and at what frequencies. At that time, you can know if the child could be a CI candidate. This would be within a week or so of birth.
Currently, you must do a trial of hearing aids. Most doctors do 6 months. During that time they use booth tests to see if there is benefit from hearing aids. If there is not significant benefit (which most audiologist, surgeons and parents would want the child aided completely into the speech banana, at 30-35 db) the child is then a CI candidate. They are able to be implanted, at the surgeons discretion, starting as young as 6 months old. I know several families who had their child receive bilateral implants between 8 and 10 months old.
