I just woke up one morning and it didn't feel right.. it got progressively worse and i made the big mistake of going to doctors who ran lots of tests, did nothing, and charged me big bucks, anyway.. This all started maybe early '82, or so, so at least 2 years before the metal hair slinging.. I never spun in like you mention, cuz I knew my neck wasn't gonna take that, but I did throw my head around a lot - and still do onstage..
Never did figure it out.. ALTHOUGH.. I do have a theory: I was playing soccer in college ('81) and was actually playing against the college varsity team - and doing pretty well.. I didn't know jack about soccer, tho.. A dude kicked a corner kick from the sideline corner and I was standing by the goal.. I stupidly tried to head butt the ball into the net, without knowing how to do it, and it hurt pretty bad.. the ball went over the top of the goal, so I didn't even score.. It hurt for a few days, then got better.. I'd say a year or so later I woke up with the neck issue..
I think possibly heading the ball smashed the vertebrae causing the beginning of the blowout of C3/4 and C4/5.. I have no proof, but it would make sense..
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..