Relatively often, when you initiate combat with it, it'll knock the person out. Some other times, it'll initiate the fight with very low damage and lag them between 1 to 2 rounds - 1 command (like trip). When used in the middle of a fight it can deal some damage (like backhand) and lag them for the same 1 to 2 rounds. But when you land some 'knock out' type cranial without actually knocking them down, you can't cranial again because they'll already be dazed from the previous blow....so I'm not actually sure how it works.

This is only my own experience. Always a good option to try it though if you can't bash, trip, misdirect, etc...