went to the re room with a headach sooooo severe.also been getting shingles in the right eye every 2 to 3 months. doctor ordered a ct without contrast an said i had a 4.2x4.0cm cystic mass in the right posterior,this was in june of this year. still have not had an mri.the report stated looks like an arachnoid cyst, not to rule out neoplasm. should i be worried. i have an appt.with neuro next month.,46 years old. does anybody know about these cyst?