Hi maryblair, and thanks for posting on the ANA Forums!
I also have a very small acoustic neuroma and had horrible vertigo and dizziness. I had fallen down numberous times and had to walk with a cane. But that was when my AN was first diagnosed. I went to a vestibular therapist (not a regular physical therapist), had a few months of treatment, and I have not had any more dizziness since, and I don't use a cane anymore. My last MRI showed no growth.
I am not a medical doctor, but my understanding is that acoustic neuroma patients can have occasional worsening symptoms even though the acoustic neuroma is not growing. So, we are told not to panic if we have occasional reoccurring symptoms. The MRI is the definitive answer to the question of how fast or slow the AN is growing or whether it is staying the same or even shrinking. Since acoustic neuromas typically grow very slowly, you probably can wait until your next scheduled MRI, especially with it at only 4mm. But, if you have any concerns, I would share them with your healthcare provider.
Best wishes on your journey!
Don