What Causes Unconsciousness While Sleeping?

I was asleep seems very deep when I wake up I found out that I have wetter the bed without any notice, I did not had a dream either. Seems as if a loose my conscious for a while. What can be the cause of this? I am 41years ,164cm height, 91 kg weight. In 1997 I had an accident I injured my neck c4 was displaced, i was kept on halo z traction for 6 weeks, then soft color support for 2 months.