Is 3 Cm Posterior Fossa Cyst Midline A Cause For Concern?

Should I be concerned if I have a 3 cm posterior fossa cyst midline which likely represents a mega cisterna magna, a developmental variant? There's no evidence of anything else odd and I have no symptoms or discomforts. Sometimes I may lose my train of thought, but not more often than most other people seem to.

I am a 48 year old female in great health. 5'6" 130 lbs. I eat pretty healthy and exercise often.