Hi Daharris!
Been there myself with the earliest MRI. The radiologists report said either acoustic neuroma or vestibular neuronitis.
I took this to Mayo Clinic and they immediately said, "AN"; .5 cm. at that time, now 1.5 cm. and watching.
Hearing has gotten worse and balance function of that side shows nil ( canal paresis ) by an ENG with calorics test.
Now, MRIs do vary and have an inherrant inaccuracy potential of + or - 1 - 2 mm.
Seems if your symptoms worsen, you should get another MRI reasonably soon. Even if they don't worsen, if it were my situation, I would want another MRI in 6 months. Make sure this is being done at a large treating facility with an ENT dept. well experienced in acoustic neuromas. It must be at least a closed tube T-3 weighted scanner and not of the newer open variety some ill informed Drs order.
Best wishes in this!
Russ