More than 450,000 children present to U.S. emergency departments with blunt head trauma each year. Nearly half of them undergo head CT, yet only 1 percent have injuries serious enough to require neurological treatment. That means the great majority are unnecessarily exposed to ionizing radiation, a known risk factor for cancer in children.
According to a 2012 British study published in The Lancet, having just two or three head CTs in childhood may triple the risk of brain tumors later in life. Another study, which appeared in JAMA Pediatrics in 2013, found that head CT was the greatest risk factor for leukemia in children under 5, at a rate of nearly 2 cases per 10,000 scans.
Children are more radiosensitive than adults are, and their longer life expectancy provides more opportunity for radiation-associated problems to develop. They are also more likely to experience cumulative damage because each dose of future radiation adds up. Thus, the challenge in emergency medicine is to balance the lifetime risk of cancer in scanned children — an estimated 5,000 cancers a year — against the detection of significant brain injury.
In 2009, the Pediatric Emergency Care Applied Research Network (PECARN) developed prediction rules to help guide such decisions. The rules, published in The Lancet, aim to identify children at high risk of clinically important traumatic brain injury (TBI) after minor head trauma.
The PECARN decision rules stratify children into two groups: those under 2 years of age and those ages 2 to 18. According to the guidelines:
- Children under 2 with a Glasgow Coma Score (GCS) of 14 or less, altered mental status or palpable head fracture are at high risk of TBI and should be scanned.
- Scanning is also recommended for older children with a GCS of 14 or less, altered mental status or signs of basilar skull fracture.
Recommendations vary for children with one or more other risk factors, including severe mechanism of injury, loss of consciousness lasting more than 5 seconds and nonfrontal scalp hematoma.
A 2014 comparison of physician practice and three decision rules, including PECARN, concluded that only physician practice and PECARN correctly identified clinically important TBI in more than 1,000 children and teens with minor head trauma. The comparison study appeared in Annals of Emergency Medicine.
Still, PECARN has limitations, mainly because it provides definitive recommendations as to what a clinician should do for high- and low-risk children but leaves some ambiguity for those at intermediate risk, says James L. Homme, M.D., assistant professor of emergency medicine and pediatrics at Mayo Clinic's campus in Rochester, Minnesota.
"The PECARN rules say patients at very low risk don't need imaging, recommend scanning all high-risk patients and leave CT scanning as an option for all other patients who fall into the intermediate risk category," he explains. "But sub-analysis of the PECARN data clearly show that within this intermediate risk group, there are varying levels of risk."
For instance, a 12-year-old child who injured his head in a sledding accident and later vomited would fall in the intermediate risk group. But if vomiting were the only symptom, the actual risk of having a clinically important TBI is 1 in 2,000, and you wouldn't scan him.
For a child with two risk factors, such as vomiting plus significant headache or severe mechanism of injury, Mayo's recommendation would likely be a period of observation before scanning and discussion with the family, Dr. Homme says.
"We must be sensitive to parents' concerns about radiation and be able to address them — whether to allay them when a study is clearly indicated or to factor in risk when a parent or caregiver wants a scan just to be sure," he explains. "Wanting to be sure is fine if there is no risk, but when there is potential risk from a test, you have to have that conversation with the family. More accurately quantifying the magnitude of the risk of injury helps in this conversation."
Mayo Clinic has developed a clinical decision aid based on PECARN data that will help providers and families more clearly identify a child's specific risk. It is currently being studied in a multicenter randomized controlled trial.
"We are refining and sharpening the guidelines to better identify the risk for kids with minor head injuries — those who aren't particularly high or low risk," Dr. Homme says. "The hope is that in the future, we will be able to provide parents and providers at the bedside with a tool that provides definitive risk estimates for the child in front of them. This will help both interested parties make decisions in a more informed way — and less based on fear and uncertainty."
He emphasizes that help is always available for clinicians struggling with CT decisions.
"I think the fear of missing a serious injury is related to frequency," he says. "The less often you see kids with head trauma, the less comfortable you are not scanning them.
"At Mayo Rochester, we are happy to take phone calls when a provider is uncertain. I love it when people call and am happy to work through questions about the guidelines. We hope to be a good resource on this subject for the entire Mayo Clinic health system."
For more information
Pearce M, et al. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: A retrospective cohort study. The Lancet. 2012;380:499.
Miglioretti DL, et al. The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risk. JAMA Pediatrics. 2013;167:700.
Kupperman N, et al. Identification of children at very low risk of clinically-important brain injuries after brain trauma: A prospective cohort study. The Lancet. 2009;374:1160.
Easter JS, et al. Comparison of PECARN, CATCH, and CHALICE rules for children with minor head injury: A prospective cohort study. Annals of Emergency Medicine. 2014;64:145.