I have no idea how many people are being diagnosed with an acoustic neuroma these days but I'm sure that access to information via the internet may be a factor, as are MRI availability, compared to some years ago, when only big-city hospitals had an MRI facility. That noted, I very much doubt that AN's have any significant association with MRI scans, much less, the mere presence of magnetic resonance imaging machinary. Radio waves are used but there is no radiation involved. Furthermore, acoustic neuroma tumors were known 100 years ago, long before the advent of MRI, cell phones, jet planes or heavy concentration of power lines.
I freely admit that I have no credible answer as to the cause of AN tumors and this is just my opinion but I have to discount much of the latter-day speculation regarding medical machinery, electronic devices, planes, power lines and excessively loud rock music being the cause when the condition existed long before any of these things were around.
Jim