My son is thirteen years all and was complaining about black out episodes. I took him to have an eye exam and on a visual field the optometrist found and inflamation on the optic nerve. He ordered me to consult a neurologist and he order a brain MRI. I just got the findings an I am very concern.

Findings: The study demostrates a well-defined cystic lesion within the posterior fossa to the right side of midline posteriorly, which measures 1.5 x 1.0 x 2.5 cm. This lesion does not enhanced after the administration of intravenous gadolium and likely represents an arachnoid cyst. No abnormal enhancing lesion are visualized. ect...

Impressio: Arachnoid cyst within the right side of the posterior fossa, as described. No other abnormality seen.

Is this very serius? What the treatment will be? Surgery?