If you’ve taken your child to the emergency department following a bump to the head, you’re there to get your child treated – and to make sure everything’s OK. CT (Computed Tomography) scans yield a lot of information, but also expose kids to radiation – not a good idea unless it’s necessary.

A study out today suggests that observation in the ER could cut down the need for, and use of, CT scans in kids with blunt head trauma, but still ensure that serious injuries are diagnosed. Researchers from Harvard and UC Davis looked at data on more than 42,000 children with minor blunt head trauma. They found that those who were observed before making a decision to order a CT scan were half as likely to have one as those who were not observed first.

Co-author Lise Nigrovic, M.D., Harvard professor and pediatric emergency medicine specialist at Children’s Hospital Boston, answered a few questions about the study:

What period of observation are we talking about here? Minutes? Hours? And what are clinicians looking for during this observation period?

During a period of monitored observation in the emergency department, clinicians watch a child with blunt head trauma for either progression or improvement of clinical symptoms such as headache, vomiting or altered mental status. Clinicians use the change of symptoms over time to decide whether to obtain a cranial CT.

We don't yet know precisely how long to observe children after blunt head trauma to be sure that all children with clinically important injury are diagnosed, and that will be the subject of future study. However, current practice guidelines for the management of head trauma suggest 4-6 hours from the time of injury.

Based on these findings, how much might implementing a policy of observation prior to making decisions about CT scans lower the number of scans kids receive each year in the U.S.?

Recent studies suggest that approximately half of children with blunt head trauma presenting to U.S. emergency departments undergo head CT scans. In our study, patients who were observed by their treating clinicians prior to CT decision-making had approximately half the CT rate of those children who were not observed after adjusting for markers of head injury severity.

What is a child’s risk from the radiation exposure in a CT scan? And is there greater cause for concern because we're talking about scanning the heads/brains of children vs. adults?

A single CT scan exposes a child to ionizing radiation, which we now know increases the lifetime risk of a lethal [cancer] malignancy. Although experts disagree as to the exact magnitude of this risk, the youngest children are at the greatest risk because their tissues are the most radiosensitive and they have a longer time for a malignancy to develop.

Nigrovic says that while head trauma is common in children, most of those who visit the ER do not have traumatic brain injuries. So it’s reasonable to take the time to monitor them first and reserve CT scans for those who truly do appear to have significant injuries. Further work, she says, will determine exactly how long children need to be observed so that significant head injuries aren’t missed, and how this might impact the amount of time families spend in the ER – and crowding in emergency departments.

Her study was published online today, and appears in the June edition of Pediatrics.