Although it has been suggested that screening of asymptomatic patients is futile,^16–18 there is evidence that stroke rates are significantly lower in treated patients when compared with untreated patients.^11,12,19 Moreover, the Denver group has demonstrated that screening and treatment of BCVI is cost effective.²⁰ Identification of a high-risk group for screening has been debated in the literature. The fundamental mechanisms of internal carotid artery injury include:

(a) cervical hyperextension or hyperflexion with rotation, stretching the internal carotid artery over the lateral articular processes of cervical vertebral bodies C1–C3;

(b) direct cervical trauma;

(c) intraoral trauma; and

(d) basilar skull fracture involving the carotid canal.^21,22

The vertebral artery is most commonly injured from C-spine injuries, especially subluxations and fractures of the foramen transversarium.²³ Analyses of screening have identified the following list of high-risk factors for BCVI:⁹

(a) an injury mechanism compatible with severe cervical hyperextension with rotation or hyperflexion;

(b) Lefort II or III midface fractures;

(c) basilar skull fracture involving the carotid canal;

(d) closed head injury consistent with diffuse axonal injury with Glasgow Coma Scale score <6;

(e) cervical vertebral body or transverse foramen fracture, subluxation, or ligamentous injury at any level, or any fracture at the level of C1–C3;

(f) near-hanging resulting in cerebral anoxia; or

(g) seat belt or other clothesline-type injury with significant cervical pain, swelling, or altered mental status.

With the improved accuracy of noninvasive screening modalities, there is a tendency to liberalize screening in an attempt to capture all injuries, rather than restricting screening to groups with the highest risk.^24–26 Broadened screening guidelines may include combined thoracic and cervical or cranial injuries, but there have not been any large-scale analyses to determine the yield of such protocols.