Skull x-ray scans after minor head injury in children younger than 2 years of age

Skull fractures and the risk of ICI

Skull fractures can develop in young children owing to their larger head-to-body ratio, thinner cranial bones, and less myelinated neural tissue.⁸ Children younger than 2 years of age with minor head injuries have a 6% to 30% chance of developing a skull fracture.^9-12 However, most of these studies are older and were done before the PECARN rule was created, meaning that this range could be overestimated. In a more recent study, Gravel et al from Canada conducted a prospective study in 1667 children younger than 2 years of age and excluded children with high-risk minor head trauma as per the PECARN rule (GCS score <15, altered mental status, or palpable skull fracture) or with suspected nonaccidental head injuries.¹³ Only 5.6% of children had a skull fracture on an x-ray scan, and none of the children in the study, including those who did not have head imaging done, developed complications or needed neurosurgical intervention.¹³ The risk of skull fracture was substantially reduced when high-risk patients were excluded from the study.

In general, the risk of developing an ICI in children younger than 17 years of age with a minor head injury is 4.1%, as reported by the Pediatric Emergency Research Canada Head Injury Study Group,¹⁴ but the incidence range of ICI associated with skull fracture following minor head trauma is wide—between 4% and 50%.^9-12,15

A prospective study in asymptomatic infants up to 2 years of age presenting to the ED with a minor head injury reported that 11% (45 of 422) had skull fractures and 28.8% of them had an associated ICI.¹² The study included children with mechanisms of injury such as motor vehicle accidents, falls, and direct blows to the head by an object; however, they did not report the severity of the mechanisms of injury.¹²

The PECARN rule considers a severe mechanism of injury to be a fall of more than 0.9 m (3 ft); a strike to the head by a high-impact object; a motor vehicle collision with patient ejection, death of another passenger, or rollover; or a pedestrian or bicyclist without a helmet being struck by a motorized vehicle. With any of those, a head CT scan should be considered.⁵

A study by Erlichman et al including children with a GCS score of less than 15 and no documented LOC, or LOC of less than 5 minutes found that one-quarter of the children with a skull fracture had an ICI.¹¹ Nonetheless, ICI associated with an isolated linear skull fracture was almost always clinically insignificant and rarely required neurosurgical intervention.^11,12

This finding was supported by a recent systematic review evaluating the number of adverse outcomes associated with isolated skull fractures in children younger than 18 years of age.¹⁶ Twenty-one studies of 6646 children with isolated skull fractures were included and only 1 child needed emergency neurosurgery, with no reported deaths.¹⁶

The variation in the risk of developing a skull fracture or an ICI related to a skull fracture in these studies could be attributed to including children who would be considered at high risk, as per the PECARN clinical rule (GCS score <15 and altered mental status), or who had a high-risk mechanism of injury. Nevertheless, most of these studies were retrospective, which may have affected the selection of patients.

Skull x-ray scan versus head CT scan

The Canadian Paediatric Society suggests screening for skull fractures in children with minor head trauma who are younger than 2 years of age and have a large, boggy hematoma.¹⁷ Skull x-ray scans have been preferred for this purpose for many years in the management of head injury, as they expose children to a minimal amount of radiation.¹⁷ In a study comparing head imaging methods to detect skull fractures in cadavers of children, high-resolution CT scans with 3D projections and “conventional CT” had a sensitivity of 71% and skull x-ray scans had a sensitivity of 63% for a single linear fracture. For multiple fractures, all 3 imaging methods had 50% sensitivity.¹⁸

Two Canadian studies evaluated skull x-ray scans in children younger than 2 years of age with minor head injuries in the ED.^13,19 In one study, none of the patients with a skull fracture needed neurosurgical intervention after assessment and follow-up. Although head imaging was not done and skull fracture was not excluded in 1022 patients, complications secondary to skull fracture were excluded.¹³ In the other study, patients with asymptomatic linear skull fractures on x-ray scans were followed; it was determined that they could have been safely discharged after 3 to 6 hours of observation in the ED instead of being admitted to the hospital.¹⁹

Using a skull x-ray scan to identify a linear fracture with a diastasis greater than 4 mm, a depressed skull fracture, open fractures, or comminuted fractures can help stratify patients for risk of CITBI and the need for an urgent head CT scan and neurosurgical consultation.¹⁹ This contributes to resource management and radiation reduction.²⁰

Finding a skull fracture and monitoring children clinically as outpatients for rare complications such as growing skull fracture, also known as an arachnoid (leptomeningeal) cyst, can help expedite referral for treatment to avoid complications such as brain herniation.^21-23

Clinical decision rules with skull x-ray scans

There is variability in identifying skull fractures using x-ray scans (1.3% to 10%).^19,24,25 In a retrospective study of 5217 children with minor head trauma, only 1.3% had a skull fracture on an x-ray scan. For children younger than 2 years, the rate was 3%. It was unclear what the indications were for skull x-ray scans.²⁴ A retrospective study from Quebec included 417 children up to 3 years of age who presented to the ED with minor head injury.¹⁹ More than one-third (37%) of them had a skull x-ray scan, and 3.6% had a skull fracture. The investigators included children who fell from less than 1 m, which is a nonsevere mechanism of injury. However, only a few patients had a cephalhematoma on examination, and the study did not specify the location of the hematoma. These patients had a lower probability of having a fracture identified on an x-ray scan.¹⁹

Members of the Pediatric Emergency Research Canada group responded to an e-mail questionnaire (response rate of 54%) about ordering skull x-ray scans for 11 clinical case scenarios of children younger than 2 years with minor head trauma. Substantial variation among practices was apparent, as 20% to 80% of respondents would have ordered x-ray scans for 6 of 11 case scenarios. Most (95%) participants said they would apply a validated clinical decision rule for detecting skull fractures if it had a sensitivity of 98%.²⁶

To reduce unnecessary imaging in the ED, Gravel et al developed a clinical decision rule limiting skull x-ray scans to children younger than 2 years of age with occipital or parietal hematoma and all children 2 months of age or younger with any hematoma. The sensitivity was 98% and specificity was 82%, and the clinical decision missed severe injury in only 1 infant. None of the patients in the study developed complications or needed a neurosurgical intervention.¹³ A larger cohort study and external validation are yet to be done.