So sorry to hear that your son is suffering.
A problem with MRI is always that you risk finding something else than what is causing you trouble. Arachnoidal cysts are believed to be mostly congenital and asymptomatic.
On the other hand your son has some symptoms (double vision) that are not really easily explained by something else (migraine for example).
His docs will now have to do some work to come up with an educated guess whether the cysts are the root of the problem or not. It will not be so easy for them. To be honest I wouldn't be surprised if the cysts really is the problem in the end.
Please try to be strong. The modern health care can do wonders. There should be no reason for this not to turn out fine for your son in the end, even if times are tough on the way.
Wish you both the best!
Hi and welcome to the Migraines & Headaches Community.
I am afraid that I dont really know anything about headaches because of cysts. Maybe someone else will come along that can give you an answer.
Please let us know what the doctor says after the appt at UCSD.