My hearing loss was gradual too. The first symptom was having difficulty hearing people on the phone on my AN side. My parents took me to an ENT, he ran a hearing test and told my parents that "I was lying" about not hearing! Of course, my parents got a second opinion, but the second opinion Dr. said that I had "virus", so nothing was done, but prescribing some meds. Can't remember the exact details because it was over 40 years ago. Finally, when I had another hearing test, of course I couldn't hear a thing on that side. The next symptoms were headaches, seeing spots, dizzyness and finally I was correctly diagnosed with the acoustic neuroma. Actually the first doctor that saw it was the Opthamologist. I was losing peripheral vision on the AN side and he actually saw the tumor through my eye. I had surgery to remove the tumor within 2 weeks of that diagnosis. The doctors said that it may have growing in my head since I was 6 years old. They don't really know - so much about these tumors were unknown at that time.
Jan D