I'm with Sticky on this one. There was a Danish rider called Stig Jarmer crashed at the Brandywell about 1993 or 94, and I remember seeing this crash footage at the time. In fact I'm pretty sure I've got it on an old video stashed away somewhere.
At that time, I was very friendly with some of the Danish riders.and Jorgen Vendelbo stayed with us when he rode in the TT in 1993/94. He watched this footage on our tv/video and told me that he knew the rider as a fellow Dane.
He also told me that he was badly injured and had to have a rod inserted into his spine, as he came into contact with a fence post when he landed.
I hope this helps solve the mystery? :?