Acute closed head trauma is easy enough – and challenging enough. There are validated decision instruments and guidelines, yet still plenty of CTs performed absent sound indications. However, the question this study addresses is slightly different: what to do with those who present in a delayed fashion following minor head trauma?
The authors probably sum it up best in a reasonably concise fashion:
“Patients presenting after 24h of injury are a potentially distinct subpopulation. They could be at lower risk, as there is evidence that patients with mild/minor head injury who have injuries requiring neurosurgery will deteriorate within 24h. Alternatively, they could be a self-selecting higher-risk group attending due to the worsening or persistence of symptoms.”
These authors reviewed 2,240 patient encounters resulting in a CT scan of the head, with a goal of winnowing it down to just those performed for a traumatic indication. Of those, 549 were performed within 24 hours of injury and 101 were delayed presentations. There were 46 (8.4%) CTs positive for traumatic injury in the acute presentations and 10 (9.9%) in delayed, while 5 and 3 patients each underwent neurosurgical intervention, respectively. So, the answer to their research question, at least in pragmatic terms, may be that the two forces balance each other out.
These authors also present “sensitivity” statistics regarding the utility of guidelines at predicting the presence of an important TBI, and quote a sensitivity of 70% based on chart review. The denominator for sensitivity would more appropriately the entire population of presentations for trauma, not simply those who underwent CT scanning. It is also probably more likely, given these patients had important TBI on CT, there may have been undocumented, guideline-compliant, indications not abstracted by chart review.
While our decision instruments for closed head injury were derived in typically an acute population, I would not yet draw any conclusions refuting their generalizability to delayed presentations.
“CT head imaging in patients with head injury who present after 24 h of injury: a retrospective cohort study”
https://www.ncbi.nlm.nih.gov/pubmed/27076439