PECARN Calculator – Pediatric Head Trauma Risk
Assess traumatic brain injury risk in children with minor head trauma and guide CT scan decisions using the evidence-based PECARN rule.
Enter age, symptoms, and mechanism of injury to stratify risk of clinically important traumatic brain injury (ciTBI) and receive evidence-based recommendations.
PECARN Calculator – Pediatric Head Trauma Risk
Assess traumatic brain injury risk in children with minor head trauma and guide CT scan decisions using the evidence-based PECARN rule.
Click any example to load it into the calculator.
About the PECARN Calculator
The PECARN (Pediatric Emergency Care Applied Research Network) rule is a validated clinical decision tool for identifying children at very low risk of clinically important traumatic brain injury (ciTBI) following minor head trauma. Developed from a large, prospective, multicenter study of over 42,000 children, it was published in The Lancet in 2009 and has since become the standard of care for pediatric head injury risk stratification in emergency medicine worldwide.
Head injuries are extremely common in the pediatric population, but the vast majority do not result in serious brain injury. Historically, CT scans were overused in children with head trauma, exposing them to ionizing radiation that carries a lifelong cumulative cancer risk. Because children are more radiosensitive than adults and have longer life expectancies, unnecessary CT scans represent a meaningful harm. The PECARN rule was designed specifically to identify the subset of children — roughly 85–90% of those presenting with minor head trauma — who can safely be observed without CT imaging.
The PECARN rule applies different criteria for two age groups: children under 2 years of age, and children 2 years of age and older. This division reflects important developmental differences in symptom reporting, injury patterns, and neurological assessment. In infants and toddlers under 2, the highest-risk features are altered mental status and palpable skull fracture. In older children (aged 2 and above), the high-risk feature is altered mental status only; palpable skull fracture and other examination findings move to the intermediate-risk category for this age group. Intermediate-risk features in each group include loss of consciousness, vomiting, severe mechanism of injury, scalp hematoma (non-frontal in children under 2), acting abnormally per the parent, and severe headache (in children 2 and older).
A 'severe mechanism of injury' is defined as a motor vehicle crash with patient ejection, death of another passenger, or rollover; pedestrian or bicyclist struck by a motorized vehicle; falls of more than 5 feet (1.5 metres) for children over 2 years, or more than 3 feet (0.9 metres) for children under 2 years; or head struck by a high-impact object. Altered mental status includes agitation, somnolence, repetitive questioning, or a GCS score of 14 or lower. These specific definitions are critical to applying the rule correctly.
The PECARN rule stratifies children into three risk groups. High-risk patients have an estimated ciTBI risk of greater than 4% and CT imaging is recommended. Intermediate-risk patients have a risk of approximately 0.9–1.0% and management involves shared decision-making with the family, considering options of CT imaging or a period of observation. Low-risk patients have a ciTBI risk below 0.02%, and CT imaging is not recommended — observation alone is safe and appropriate. The rule has high sensitivity (exceeding 99%) and negative predictive value in validated studies, making it reliable for ruling out ciTBI in low-risk patients.
PECARN Calculation Examples
| Scenario | Risk Level | Recommendation |
|---|---|---|
| 1-year-old with palpable skull fracture after fall, severe mechanism | HIGH RISK | CT recommended. Palpable skull fracture is a high-risk feature in children < 2 years. |
| 1-year-old, non-frontal scalp hematoma, acting abnormally per parent | INTERMEDIATE RISK | Consider CT or observe. Intermediate features present in child < 2 years. |
| 7-year-old with minor bump, no symptoms, no risk factors | LOW RISK | CT not recommended. No high or intermediate risk features — safe to observe at home. |
| 10-year-old with vomiting and severe mechanism of injury | INTERMEDIATE RISK | Consider CT or shared decision-making. Vomiting + severe mechanism in child ≥ 2 years. |
How to Use the PECARN Calculator
- Enter the child's age in years and months. The calculator automatically selects the PECARN criteria appropriate for children under 2 years or 2 years and older.
- Answer each clinical question (Yes/No) based on careful assessment and caregiver report. Loss of consciousness, vomiting, severe headache, altered mental status, acting abnormally, and post-traumatic seizure should reflect the patient's presentation at the time of evaluation.
- Assess for physical exam findings: palpable skull fracture on exam and non-frontal scalp hematoma (for children under 2) are key examination points.
- Select 'Yes' for severe mechanism of injury if the event involved: motor vehicle crash with ejection/rollover, pedestrian/cyclist struck by vehicle, fall > 3 feet (under age 2) or > 5 feet (age 2+), or head struck by high-impact object.
- Click 'Assess Risk' to receive the PECARN risk category (High, Intermediate, or Low) along with the estimated ciTBI risk percentage and a clear recommendation regarding CT imaging. Always integrate the result with the full clinical picture and family discussion.
Frequently Asked Questions
What is ciTBI?
ciTBI stands for clinically important traumatic brain injury. It is defined as brain injury identified on CT that requires neurosurgical intervention, intubation for more than 24 hours, hospitalization for two or more nights due to the head injury, or death. It is a more specific endpoint than any abnormality on CT, focusing on injuries with real clinical consequences.
Why are the PECARN criteria different for children under 2 years?
Children under 2 years have different anatomy, different mechanisms of injury, and limited ability to report symptoms such as headache. They are also at higher risk for occult skull fractures and non-accidental trauma. The PECARN study prospectively validated separate decision rules for each age group to optimize sensitivity and specificity in each population.
What qualifies as a severe mechanism of injury?
A severe mechanism includes: motor vehicle crash with patient ejection, death of another passenger, or rollover; pedestrian or bicyclist struck by a motor vehicle; fall of more than 5 feet (children ≥ 2 years) or 3 feet (children < 2 years); or head struck by a high-impact object such as a bat or rock. Correctly identifying a severe mechanism is critical because it places an otherwise low-risk child into the intermediate-risk category, potentially warranting CT consideration.
Can the PECARN rule be used for all pediatric head injuries?
The PECARN rule is validated for children with minor head trauma (GCS ≥ 14) presenting within 24 hours of injury. It should not be applied to children with penetrating trauma, pre-existing neurological disorders, obvious open skull fractures, bleeding disorders, ventriculoperitoneal shunts, or those who were sedated or intubated before the assessment.
What does 'intermediate risk' mean in practice?
Intermediate risk means that the estimated ciTBI probability is approximately 0.9–1.0%. Neither immediate CT nor blanket observation without consideration is automatically appropriate. Clinical judgment, the reliability and experience of caregivers for home observation, time since injury, geographic access to follow-up care, and family preference all factor into the decision. Many clinicians use a period of ED observation, after which imaging is decided based on clinical trajectory.
How reliable is the PECARN rule?
The PECARN rule has been prospectively validated in studies involving tens of thousands of children and has a sensitivity exceeding 99% for identifying ciTBI. It has been externally validated in multiple countries and is endorsed by the American Academy of Pediatrics and major emergency medicine organizations. Its routine use has demonstrably reduced CT scan rates in children without missing clinically important injuries.