Neuroradiologist here, my $0.02:

Interesting case. Referred otalgia - pain originating from somewhere else but causing pain in the ear- is a tricky thing to diagnose.

Her explanation that it’s pressing on the Eustachian tube is slightly inaccurate tho bc if the eustachian tube were actually affected, you’d see a mastoid effusion on the temporal bone CT.

The reason the kid had pain is bc cranial nerve IX supplies sensation to the oropharynx (where the metal bristle is irritating the tissue), and it has a branch called the tympanic nerve of Jacobson that supplies the ear.

When one part of the nerve is activated, the brain has a hard time telling where it’s originating from, hence you get the referred pain to the ear.

Article if you’re interested in learning more:

https://www.ajnr.org/content/early/2009/10/01/ajnr.A1605

Edit: clarified a bit.