Clinical investigations that provide Class I evidence involving nearly 40,000 patients, plus Class II and III evidence studies involving more than 5000 patients, convincingly demonstrate that asymptomatic patients do not require radiographic assessment of the cervical spine after trauma. The combined negative predictive value of cervical spine x-ray assessment of asymptomatic patients for a significant cervical spine injury is virtually 100% (2, 4-6, 9, 14, 16-18). In contrast, the reported incidence of cervical spine injuries in the symptomatic patient ranged from 1.9 to 6.2% in these Class I evidence studies. Symptomatic patients require radiographic study to rule out the presence of a traumatic cervical spine injury before the cervical spine immobilization is discontinued (2, 4-6, 9, 14, 16-18). The type and extent of radiographic assessment of symptomatic patients after trauma is reviewed in Chapter 5.