My Husband's 15 Y/o Son Was In A Car Accident

My husband's 15 y/o son was in a car accident approximately 1 mon.ago. He was taking to hospital and was told he had a head concussion, and needs to be seen by a specialist. To make a long story short, he had an MRI done and they told my husband's ex-wife that he has a cyst on the brain. Can this be from the accident or do you think this was pre-existing. At first they told her this wasn't a big deal but today they called her back and said, He needs a follow up appt., no physical contact and if cyst doesn't shrink w/I 6 months then he would need to undergo surgery to have it removed.