When my daughter decided she wanted an implant for her other ear, we were told that since that cochlea was fully ossified (filled with bone), there was no way to predict how well it would work, or how long it would take to get maximum benefit. With most implant proceedures, two years is the general time frame between implantation and maximum benefit. Since she got her first implant before that cochlea ossified, it works very well. Ossified cochleas are a different beast entirely.
What she was able to do after two months with her original implant, took a year with her second implant. She has a complete insertion of the electrode array in her left ear, but only has 11 electrodes in her ossified right cochlea. Most of them tend to stimulate her facial nerve rather than her auditory nerve. Out of 11 electrodes, only 5 electrodes are active. You would think that this has been a complete waste of time and money. You would be completely wrong.
Having two working ears, even though one doesn't work well, has made a big improvement in her ability to hear in noise. And really, most of life exists in noise. Even before she could distinguish sound in her right ear, she was showing marked improvement in her overall hearing. At her 6 month check last summer, her overall hearing was 7% better with both implants than it was with her original implant alone. And at her check yesterday, she did really well on the closed set words even at 15 words.
We never really expected her right ear to work very well by itself, and were mostly hoping for what we have already gotten, better hearing in noise. But her brain is beginning to make sense of sound in that ear by itself, and it should continue to improve. Absolute bonus.
If you lost your hearing from meningitis, and you have ossified cochleas, you will want to think very carefully before getting implants. Progress will be extremely slow, and you will have to work VERY VERY HARD to get any use out of them. I would only recommend implants if you have a very strong dedication to wanting to hear, and you are willing to persevere. The good news is that it is possible. Just not easy.