I met someone with bilateral CI implants who actually worked at the
House Ear Institute in Los Angeles, and she was one of the older patients there. When she was starting out some 20+ years ago, she had some problems with headaches and also her facial muscles were twitching. She went back in to see her CI audiologist. The audiologist did some adjustments and the problem went away. Later on, she needed her CI to be replaced and they put in a new one. The last time I spoke with her, she was planning on upgrading and replacing her current CIs. So yes, they are removable and can be upgraded to newer models. Mind you, money will be a factor and medical insurance companies will try to avoid the cost.