What was attached to this guy's head (medical)?

An older fella gave a tour the other day for the Park Service. He had hearing aids in both ears, worn externally. The one on the right had what looked to be a wire coming off of it, which was attached to a disc about 1" in diameter, which in turn appeared to be actually attached to his head, up and slightly toward the back of his head. Curiosity makes me ask what that might be: something to do with his balance?

Cochlear impant

This. They’re getting quite common.

Obviously, “impant” → “implant”

The cord is excessively long and the placement uncomfortable for the Cochlear In-Pants.

Not to mention the potential noise interference.

Well, an inpant would be a very different kind of implant.

Thanks. I’d never seen one before.