OBJECTIVE: Despite high-quality paediatric head trauma clinical prediction 
rules, the management of otherwise asymptomatic young children with scalp 
haematomas (SH) can be difficult. We determined the risk of intracranial injury 
when SH is the only predictor variable using definitions from the Pediatric 
Emergency Care Applied Research Network (PECARN) and Children's Head Injury 
Algorithm for the Prediction of Important Clinical Events (CHALICE) head trauma 
rules.
DESIGN: Planned secondary analysis of a multicentre prospective observational 
study.
SETTING: Ten emergency departments in Australia and New Zealand.
PATIENTS: Children <2 years with head trauma (n=5237).
INTERVENTIONS: We used the PECARN (any non-frontal haematoma) and CHALICE (>5 cm 
haematoma in any region of the head) rule-based definition of isolated SH in 
both children <1 year and <2 years.
MAIN OUTCOME MEASURES: Clinically important traumatic brain injury (ciTBI; ie, 
death, neurosurgery, intubation >24 hours or positive CT scan in association 
with hospitalisation ≥2 nights for traumatic brain injury).
RESULTS: In children <1 year with isolated SH as per PECARN rule, the risk of 
ciTBI was 0.0% (0/109; 95% CI 0.0% to 3.3%); in those with isolated SH as 
defined by the CHALICE, it was 20.0% (7/35; 95% CI 8.4% to 36.9%) with one 
patient requiring neurosurgery. Results for children <2 years and when using 
rule specific outcomes were similar.
CONCLUSIONS: In young children with SH as an isolated finding after head trauma, 
use of the definitions of both rules will aid clinicians in determining the 
level of risk of ciTBI and therefore in deciding whether to do a CT scan.
TRIAL REGISTRATION NUMBER: ACTRN12614000463673.