my mom is in the mid stages of EOAD, and she is only 54. I would definitely focus on that, and learn everything you can now. One of the best places to do this is alz.org. They have a wealth of information, and message boards that are SO informative and supportive. I am 30 years old and my mother's full time caregiver, and this site has really made a difference. Best of luck! Please check out that sight!
It is important for you to decide if the symptoms are due to early onset Alzheimer's disease or the cyst. The symptoms due to the Alzheimer’s disease are more related to cognition, memory, etc. A cyst may produce similar symptoms, but it is usually an acute or sub acute finding.
In all probabilities, your cyst is an incidental finding when the MRI was done. Alzheimer's disease is the one you should focus on. Aricept is a good drug. You need to enroll in some Alzheimer's clinic / Memory Clinic. Have regular visits to the doctor.