cephalitis

A. your question troubled me... from what i know of bone development - what you say can very much happen but i never heard of a case like that.and i looked a bit about maybe some information about it, but i'm pretty sure that the name you gave is not the disease that she has, it's just a description. Cranial means skull, Trans means cross over and Annular means ring. but if you'll find the right name, or if it is really the real name, here is a bit of places you might find information-

http://www.merck.com/mmhe/sec05.html

http://www.nlm.nih.gov/medlineplus/bonediseases.html

A. An arachnoid cyst that leads to symptoms usually needs treatment. Mild symptoms as you suggested are ok to left untreated however gradual onset of new symptoms may arise such as seizures, paralysis and other complications, therefore once symptoms occur one should consider treatment.