The report I read also so severe head trauma, but said he had severe swelling at the brain stem which is like shaken baby syndrome. That is what Dale Earnhardt died from and a local sprint car driver around here died from. It caused by severe movement between the head and the stem which looks like what happened if you watch it in slow mo.
Last I heard on Thumpertalk, he had surgery to remove all of the excess fluid that leaked into his brain. No broken neck/jaw; but he is still in a coma.
We watch these guys perform super human tricks now a days and think they are invincible. Unfortunatley an event like this reminds us of the extreme danger these guys face.
RIP... me and my cousin have done motocross since around the age of 8 and he went on to doing freestyle competitively. He died last summer losing control of his motorcycle due to head trauma as well.