Most strokes from blunt cerebrovascular injury (BCVI) occurred at a median time of 48 hours. If other injuries allow it, the earlier antithrombotic therapy can be started, the better for preventing stroke.
Whole body CT vs selective CT in children with trauma did not result in mortality benefit. This large, retrospective study with propensity matching suggested that any additional injuries found on pan-CT may have been either not life-threatening or did not change management to produce mortality benefit.
Getting an MRI for back pain does not reduce recurrent patient visits within a week. The only time we should get an MRI for back pain in the ED is if there is a clinical concern that the findings may prompt emergent surgery, such as for cauda equina, epidural abscess, or impinging mass (may need radiation), etc.