Facial pain usually comes from a tooth, sinuses, tmj, lymph nodes, and less commonly ears. The remaining structure is the parotid. Very rarely, facial pain is due to a bony skull lesion.
The patient’s pain is where her parotid is. To verify the dx, you can (1) do a CT, (2) try to push pus out of Stensen’s duct [I never see this, largely because most parotitis is not purulent], or (3) do nothing. I usually scan if I feel a lump (mass/abscess).
The dx of common childhood contagious disease nowadays is so complicated, requiring blood tests, imaging, etc. There was a measles case in the nejm that got a ridiculous amount of tests (http://www.nejm.org/doi/full/10.1056/NEJMcps1413402). In the old days, your doctor probably said, “oh you have measles, mumps, etc.” and sent you home with a lollipop.
Most parotitis I see are viral, but not mumps. I have not had a mumps outbreak in my area despite occasional spikes in cases of parotitis and other salivary gland infections. Most patients get better with ibuprofen, though there is a temptation to throw abx at the patient. I usually send these patients for ent follow-up. Most pcps have no idea what to do with parotitis nowadays.
On this patient’s scan, the L parotid is obviously enlarged, despite the lack of swelling on exam. I do iv contrast in case there’s an abscess. She was sent home with ibuprofen and got better after a few days.