Since the neurologist said to watch it if it was not causing him many problems, and he is having some problems, I'd take him back to the neurologist. If you don't like the answer from that one, then take him somewhere else and get a second opinion.
I have asked if the headaches and nausea is related and they told me that they did not think so. I also asked the doctor if he thought it might be hormones, he then told me if he was a girl yes but boys don't have problems as they approach teenage years. I really find that hard to believe. But then again I am not a doctor. I really don't know where to go from here. Noone seems to give me any answers. I really appreciate your thoughts and prayers.
The cyst could be causing his equillibrium to go off which can cause nausea. I have a nephew who went through a phase of needing pepto if he was doing something different (like visiting his aunt) It could be anthing. Did you ask the doctor if the cyst could cause the nausea?
PS: Caffeine can cause cysts, although I'm not sure if it has any effects on that kind of cyst.
You're in my thoughts and prayers.