In 2012 I experienced a sudden hearing loss in my right AN ear during my watch-wait period, about 2 months after initial diagnosis by MRI. Prior to the sudden loss, I had about 60% good hearing in that ear, which wasn't great but it was serviceable. My loss occurred on a day when I had a series of three flights to get from my home in PA to a conference in San Diego. I don't know exactly when it happened, but I know that the morning of my flights my hearing was its usual level, but when I got to the conference hotel it had gotten a lot worse (as soon as I walked into the hotel lobby I ran into some old friends, and had a lot of difficulty understanding with a lot of people conversing all around me). I had trouble hearing throughout the 3-day conference, but didn't realize I had gone deaf in the AN ear until the flight home. Shortly after take-off from San Diego, I put my earbuds in. The right earbud didn't seem to be working, and I futzed around with it for a few minutes until I put it in my left ear and realized the earbud was working fine, it was my right AN ear that wasn't working.
Upon returning home I called my local ENT. He had me come right in, and assured me that my sudden hearing loss was not due to the AN but to the flights, which is what I was thinking. Apparently, people often experience altitude/pressure related hearing loss which usually self-corrects but sometimes doesn't. He prescribed a multi-day round of steriods, the usual remedy, but it didn't work. So he prescribed another two-week long round of steriods, which also didn't work (steriods are no fun). I was then transferred to another ENT who has more experience with AN patients. He said no more steriods. It's very rare, but the tumor can press against the blood supply to the acoustic nerve and cut it off, killing the nerve and hence the deafness. He thinks that's what happened to me, and he's probably right as I've been deaf in that ear ever since.
No hearing on one side is much worse than partial hearing on that side, in ways that hearing professionals don't seem to grasp (every ENT and audiologist I've met has good hearing on both sides). Two years ago I tried a Cros device for my deaf ear, a microphone that transmits the sound on that side to a hearing aid in the good ear. It didn't work very well for me. A couple of weeks ago I had a hearing test with another audiologist, who urged me to try the Cros device again. She says the technology has improved a lot in the last 2 years. I have another appointment with yet another ENT tomorrow, and I'll be interested in what he thinks about trying the Cros again, and if there are any alternatives. Because of the continual challenges of single-sided deafness, I'll probably give the Cros another try and hope for the best.