I had my first MRI and was diagnosed with AN in November 2014. I had such a frightening experience in the MRI machine, due to anxiety and claustrophobia, i didn't go back for the 6 month repeat. Finally got up the guts to make another attempt in April 2017, different, slightly bigger machine. That's when doctor said AN had grown a little, and destroyed the fundal cap (which to my understanding is CSF barrier) and now had extension into cochlear aqueduct. AN was 5.3mm x 3.2mm on first report in 2014, then 6x4x4mm on 2nd report in 2017.
I haven't had another MRI since that one. Seems like there's no reason to. I know the thing is still there, maybe a little bigger now, but maybe not. And I know I just have to live with the symptoms I have. I sincerely feel grateful that it's not growing out the CPA end of the IAC and impinging on the brainstem, which of course is the most common direction they grow (95% of the time according to doc). I have huge empathy for people struggling with treatment decisions and the aftermath of surgeries that don't go quite as expected.
*April15/2019: I just learned today that I had misunderstood the fundal cap issue. It is not a separate structure or barrier, but rather a fluid-filled space. If it's not there, it just makes things more difficult for the surgeon, and lessens the chances for a successful outcome. I apologize for having passed along incorrect information.