Hi, i had a problem like this, i still do in fact. The first mri i had showed what they thought was a cycst, turns out that it was grade 2 astrocytoma. They had a very hard time telling the difference between a cycst and a tumor, the only reason they even found it was when i started to pass out, and have sezuires. The tumor was larger, 19X20X16mm. But because of the trouble i was having they took it out, it was then that they found out what it really was. I now have had two surgeries and i mri today showed that it has come back again. Go to another doctor, you have to ask them and sometimes show them what you want. From what i have dealt with i know they will dance around the issue till they have to do something to save you. It's really hard to tell what parts of the brain do what, the only way to really know is by haveing a fMRI done, that way you can see what parts do what, everyone is different. My tumor seems to be in the same area, but on the left side, but it has shut down my reproductive organs. If you want real answers try Duke Hospitial in North Carolina, they have some of the best Doctors there.
Good luck
Thanks for the info. All my life I have feared having a problem in my brain. I know what you must be going thru with this. Best of luck to you.