I veered off highway hit something very hard - head hit steering wheel, 3 inch gash and concussion...was rendered unconscious; air bags did not deploy even though impact damage was very severe. thus rendered unconscious I was not able to brake and avert damage to vehicle. Was transported to local hospital... was admitted and held for two days for tests and observation. Reported to GMC Corporate via telephone and was told they had no interest in evaluating. Suggested that my information was anecdotal and could not be evaluated. Not with standing... photos, police officer contact and significant trauma to head via the bags not deploying. My belief is impact was sufficient to deploy air bags and thereby avoiding head injury.. concussion.