This is another one of those cases where a direct approach to the Medical Dept at the CAA would be best, and should be made earlier rather than later, preferably before any lessons were undertaken (just avoids more disappointment if you enjoyed the first few lessons even more than you thought you would ! ).
The obvious two factors which would give cause for concern, and which would be carefully assessed on an individual basis are hearing and proprioception (balance). A full history of the background would be required, along with reports from specialists and surgeons. The CAA have their own consultants to advise in areas such as ENT as well.
Suggest you write to the CAA giving a precis of your history, and they'll advise you what further information they would require. If you want to use e-mail, the address is here
Email | Medical | Safety Regulation
If it's of any consolation at this stage, having a cochlear implant would not seem likely to me to be one of the areas where a total and absolute bar would apply from the very beginning (eg - insulin diabetes, epilepsy, etc). So it definitely is worth your writing to ask. Good luck !