Regarding trigeminal anesthesia, can you explain what is "balaclava helmet anesthesia" and what is "snout anesthesia"?

Complicated: Snout anesthesia was invented initially for pigs. A plastic cone device was fitted on the snout so, they could breath the gas." balaclava" is a metal frame attached to the head leaving the face free to accommodate a mask like the one above. In this way the head cannot move. It is used in stereotactic brain surgery to avoid even tiny movements which in this case can be very harmful even lethal.