Azathioprine, along with pyridostigmine, has been a game changer for me.  I have experienced no hearing loss, and all previous symptoms are well under control.  The azathioprine was added after a serious myasthenic crisis event that had me in the hospital for 14 days.  During hospitalization I received the IVIG treatment and was also put on prednisolone, but was able to wean off of it after about six months.