Hello AJ - and welcome. Of course, the fact that you have an acoustic neuroma is certainly not welcome for anyone, but I'm pleased that you found the ANA website and decided to register and post.
At 4 cm, your AN is large, as mine was. I also underwent the 'retrosigmoid approach' removal surgery, plus follow-up irradiation to destroy the remaining tumor's DNA. It all went quite well, as I trust your surgery will. We're an eclectic group from all over the U.S. and Europe, including the U.K. and we stand ready to answer whatever questions we can (we're not doctors) and offer our suggestions when appropriate. There is a wealth of experience here (as AN patients) offered by caring, compassionate people with a positive attitude and a keen sense of humor. Please feel free to use the forums as a resource as you prepare for your upcoming surgery.
Jim