Can shingles occur on cranial nerves without a single rash or symptom and cause post-herpetic neuralgias silently?

Unlikely. Some form of rash or sores should be present for shingles. You may have trigeminal neuralgia. This is a pain condition that usually presents with brief episodes of pain along the course of the Trigeminal Nerve or one its branches or divisions. It can be very painful-similar to a post-herpetic neuralgia.