In general, most cysts in the pineal region are common and benign. As for the comment about your cerebellar tonsils, it could mean a Chiari Malformation, which could manifest as headaches (often accompanied by swallowing difficulties and sensory disturbances in the arms and legs) or no symtoms. Lastly, the comment of enlarged third and lateral ventricles could be normal if you're older or could suggest a phenomenon called hydrocephalus. Hydrocephalus is a result of a distubance of cerebrospinal fluid resorption or production or a blockage of fluid flow. I would suggest that you see a neurologist to help you go over your findings.
Do you have any symptoms?
yes i have severe headaches since april 2008