Mandy,
Facial palsy after an AN excision or radiation is not technically Bell's palsy. Bell's palsy is idiopathic, meaning "cause unknown" (however, I will contradict myself to say that most experts now agree it is caused by a viral infection). Think of facial palsy as a general term and Bell's palsy a specific diagnosis. They both have the same effect, and that is what matters. Many doctors don't distinguish the 2 for this reason. Generally most Bell's palsy cases tend to be less severe than most AN-caused facial palsy cases, but that is changing because of improvements in microsurgery and radiation therapy , so less severe paralysis is more commonly seen nowadays. Again, I am speaking generally. As stated above, every one's case is different!
So, you can have "facial palsy" due to AN surgery, due to Lyme disease, due to trauma, d/t inner ear infection, etc., etc. On the other hand, Bell's palsy comes on without a clear cause and is considered a diagnosis of exclusion (other causes ruled out).
Hope that helps,
Todd