You will find good information on the website of the American Cochlear Implant Alliance.
https://www.acialliance.org Medicare generally covers the cost of cochlear implantation if the person has been deemed a candidate. If there is a cochlear implant center in your area, go there for testing.

The mission of the American Cochlear Implant (ACI) Alliance Foundation is to advance access to the gift of hearing provided by cochlear implantation through research, advocacy and awareness.