Background: Blunt head trauma is a common reason for medical evaluation in the pediatric Emergency Department (ED). The diagnostic work-up for skull fracture, as well as for traumatic brain injury, often involves computed tomography (CT) scanning, which may require sedation and exposes children to often-unnecessary ionizing radiation. Skull fractures are strongly associated with underlying intracranial bleed. Ultrasound has been used for the diagnosis of long bone fractures and various studies have been done to evaluate the utility of ultrasound for skull fractures.
Objectives: The aim of this study was to determine the utility of Skull ultrasound in the diagnosis of fracture in pediatric patients with closed head injury. We performed a systematic review and meta-analysis and used a test–treatment threshold model to identify diagnostic findings that could rule in/out skull fracture and decrease the need for CT scan for closed head injury.
Methods: We searched PubMed, EMBASE, and SCOPUS up to 2018 for studies on ED pediatric patients with closed head injury. Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS-2) was used to evaluate the quality and applicability of included studies. Positive and negative likelihood ratios (LR+ and LR–) for diagnostic modalities were calculated and when appropriate data was pooled using Meta-DiSc.
Results: Six studies were included encompassing 342 patients with a weighted prevalence of skull fractures of 36%. Studies had variable quality using the QUADAS-2 tool with most studies at high risk of partial verification bias. Study heterogeneity were low allowing for pooling of operating characteristics. The pooled sensitivity (91%) and specificity (96%) resulted in pooled LR+ (16.3) and LR- (0.14). Using the weighted prevalence of skull fractures across the studies as a pre-test probability (36%), then a positive skull ultrasound would increase the probability to over 90%, but a negative test would still leave the probability of a skull fracture of 7%. To achieve a post-test probability a skull fracture to ~2%, would require a negative skull ultrasound in a patient with only a pre-test probability of ~15%.
Conclusion: A positive skull ultrasound significantly increases the probability of a skull fracture, while a negative study can only markedly decrease the probability if the pre-test probability is very low.