Has anyone heard of shingles causing hearing loss?

My Mom had a bad case of shingles and within a week lost almost half of her hearing, most of it overnight. It has not returned and she now uses a hearing aid and copes the best that she can.

I'd sure like to understand what happened to her and, of course, find out if there's anything we can do to a.) help her now, and b.) prevent it from happening again.

Cheers,
Anka