Summary: No CTA for isolated cervical seatbelt sign.

Good blog post.
http://wueverydayebm.blogspot.com/2014/07/does-cervical-seatbelt-sign-mandate.html
Take Home:
CT-angiogram is not necessarily indicated based on the finding of a cervical seatbelt sign alone in the absence of significant hematoma, neurologic symptoms, or other traumatic injuries.

EAST Guideline:
https://www.east.org/education/practice-management-guidelines/blunt-cerebrovascular-injury
What patients are of high enough risk, so that diagnostic evaluation should be pursued for the screening and diagnosis of BCVI?
1. Patients presenting with any neurologic abnormality that is unexplained by a diagnosed injury should be evaluated for BCVI.
2. Blunt trauma patients presenting with epistaxis from a suspected arterial source after trauma should be evaluated for BCVI.
3. Asymptomatic patients with significant blunt head trauma as defined below are at significantly increased risk for BCVI and screening should be considered. Risk factors are as follows:
* Glasgow Coma Scale score ≤8;
* Petrous bone fracture;
* Diffuse axonal injury;
* Cervical spine fracture particularly those with (i) fracture of C1 to C3 and (ii) fracture through the foramen transversarium;
* Cervical spine fracture with subluxation or rotational component; and
* Lefort II or III facial fractures

From EAST Guideline:
An isolated cervical seat belt sign without other risk factors and normal physical examination has failed to be identified as an independent risk factor in two retrospective studies and should not be used as the sole criteria to stratify patients for screening.
References:
https://www.ncbi.nlm.nih.gov/pubmed/12013287
https://www.ncbi.nlm.nih.gov/pubmed/12013287

Alternate Screening Guidelines: