When is it safe to forego a CT in kids with head trauma?

ILLUSTRATIVE CASE

An anxious mother rushes into your office carrying her 22-month-old son, who fell and hit his head an hour ago. The child has an egg-sized lump on his forehead. Upon questioning his mom about the incident, you learn that the boy fell from a seated position on a chair, which was about 2 feet off the ground. He did not lose consciousness and has no palpable skull fracture—and has been behaving normally ever since. Nonetheless, his mother wants to know if she should take the boy to the emergency department (ED) for a computed tomography (CT) head scan, “just to be safe.” What should you tell her?

Traumatic brain injury (TBI) is a leading cause of childhood morbidity and mortality. In the United States, pediatric head trauma is responsible for 7200 deaths, 60,000 hospitalizations, and more than 600,000 ED visits annually. 2 CT is the diagnostic standard when significant injury from head trauma is suspected, and more than half of all children brought to EDs as a result of head trauma undergo CT scanning. 3

CT is not risk free
CT scans are not benign, however. In addition to the risks associated with sedation, diagnostic radiation is a carcinogen. It is estimated that between 1 in 1000 and 1 in 5000 head CT scans results in a lethal malignancy, and the younger the child, the greater the risk. 4 Thus, when a child incurs a head injury, it is vital to weigh the potential benefit of imaging (discovering a serious, but treatable, injury) and the risk (CT-induced cancer).

Clinical prediction rules for head imaging in children have traditionally been less reliable than those for adults, especially for preverbal children. Guidelines agree that for children with moderate or severe head injury or with a Glasgow Coma Scale (GCS) score ≤13, CT is definitely recommended. 5 The guidelines are less clear regarding the necessity of CT imaging for children with a GCS of 14 or 15.

Eight head trauma clinical prediction rules for kids existed as of December 2008, and they differed considerably in population characteristics, predictors, outcomes, and performance. Only 2 of the 8 prediction rules were derived from high-quality studies, and none were validated in a population separate from their derivation group. 6 A high-quality, high-performing, validated rule was needed to identify children at low risk for serious, treatable head injury—for whom head CT would be unnecessary.

STUDY SUMMARY: Large study yields 2 validated age-based rules

Researchers from the Pediatric Emergency Care Applied Research Network (PECARN) conducted a prospective cohort study to first derive, and then to validate, clinical prediction rules to identify children at very low risk for clinically important traumatic brain injury (ciTBI). They defined ciTBI as death as a result of TBI, need for neurosurgical intervention, intubation of >24 hours, or hospitalization for >2 nights for TBI.

Twenty-five North American EDs enrolled patients younger than 18 years with GCS scores of 14 or 15 who presented within 24 hours of head trauma. Patients were excluded if the mechanism of injury was trivial (ie, ground-level falls or walking or running into stationary objects with no signs or symptoms of head trauma other than scalp abrasions or lacerations). Also excluded were children who had incurred a penetrating trauma, had a known brain tumor or preexisting neurologic disorder that complicated assessment, or had undergone imaging for the head injury at an outside facility. Of 57,030 potential participants, 42,412 patients qualified for the study.

Because the researchers set out to develop 2 pediatric clinical prediction rules—1 for children <2 years of age (preverbal) and 1 for kids ≥2—they divided participants into these age groups. Both groups were further divided into derivation cohorts (8502 preverbal patients and 25,283 patients ≥2 years) and validation cohorts (2216 and 6411 patients, respectively).