π§ PECARN Head Injury Calculator
Should this child get a head CT? The validated rule.
For informational purposes only, not medical advice. Consult a healthcare professional.
PECARN, the Pediatric Emergency Care Applied Research Network, derived one of the most validated decision rules in emergency medicine from over 42,000 children with head trauma. It answers the daily dilemma of pediatric head injury: which children need a head CT and which can be safely observed without radiation. The rule splits at age 2, uses six predictors per group, and identifies children at very low risk of clinically important traumatic brain injury. This calculator applies the rule for study and clinical reference.
How to Use This Calculator
Pick the age group, then check each PECARN predictor that is present. The rule is binary: any predictor present changes the recommendation.
Select under 2 or 2 and older. The two age groups have different predictor lists because infants cannot report headache or vomiting reliably.
Check every predictor honestly. Severe mechanism includes car crash with ejection, falls over 3 feet for young children, and high-impact object strikes.
Read the recommendation. Zero predictors means very low risk and CT not recommended; any predictor means CT is recommended or should be considered with observation as an option.
How the Math Works
For children under 2, the six predictors are altered mental status, palpable skull fracture, non-frontal scalp hematoma, loss of consciousness for 5 or more seconds, severe mechanism, and not acting normally per parents. For 2 and older, they are altered mental status, any loss of consciousness, severe mechanism, vomiting, severe headache, and signs of basilar skull fracture. In the derivation study, children with none of the age-appropriate predictors had a risk of clinically important brain injury under 0.05 percent, with a negative predictive value above 99.9 percent. Any single predictor moves the child out of the very-low-risk group into CT-recommended or observation-versus-CT territory depending on the specific predictor.
Worked Example
A 7-year-old falls off a bike, cries immediately, has no vomiting, no headache, normal alertness, and a frontal bump. That is 0 PECARN predictors present, so the calculator returns CT not recommended (very low risk). In the PECARN study, children like this had a clinically important brain injury rate under 1 in 2,000, which is why the rule supports observation over CT and its radiation.
Reading Your Result
Zero predictors is the money result: very low risk, observe, and skip the CT. One or more predictors does not mean the child has a brain injury; it means the risk is high enough that CT is recommended, with brief observation as a reasonable alternative for isolated lower-risk predictors like vomiting alone. The rule applies to minor head trauma within 24 hours with GCS 14 to 15. It does not apply to trivial injuries, penetrating trauma, known brain tumors, or children with bleeding disorders, and concerning exam findings always override any score.
| Predictors present | Risk | PECARN recommendation |
|---|---|---|
| 0 | Very low (under 0.05%%) | CT not recommended |
| 1 or more | Elevated | CT recommended, or observation vs CT |
Limitations
PECARN guides the CT decision; it does not diagnose brain injury and never replaces the physical exam. The rule was derived in emergency departments for children seen within 24 hours of injury. Deterioration after scoring, concerning mechanisms like suspected abuse, and parental concern all warrant evaluation regardless of the count. This is an educational reference for clinicians, students, and informed parents, not a substitute for emergency assessment.
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Related tools: revised trauma score calculator pediatric blood pressure checker shock index calculator.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the PECARN rule?
A validated decision rule for children with minor head trauma that identifies who needs a head CT. Derived from 42,316 children in 25 emergency departments, it uses six age-specific predictors and finds a very-low-risk group where CT can be safely avoided. It is among the most studied rules in pediatric emergency medicine.
What counts as a severe mechanism?
Motor vehicle crash with ejection, death of another passenger, or rollover; pedestrian or bicyclist struck by a motorized vehicle; falls over 3 feet for children under 2 and over 5 feet for older children; and high-impact object strikes to the head. These mechanisms carry enough force to injure the brain even when the child looks well.
Why are there two age groups?
Because infants cannot report symptoms. A 7-year-old can say their head hurts and describe vomiting; a 10-month-old cannot. The under-2 list therefore relies on observable signs like scalp hematoma location and parental report of abnormal behavior instead of headache and vomiting.
What is clinically important traumatic brain injury?
The outcome PECARN was designed to catch: death from head injury, neurosurgery, intubation over 24 hours, or hospital admission of 2 nights or more for the head injury. The rule is tuned to miss almost none of these, which is why the negative predictive value exceeds 99.9 percent.
Does a normal PECARN score mean no concussion?
No. The rule predicts injuries that need CT-level intervention, not concussion itself. A child can have a concussion with zero predictors and a normal CT. Concussion is a clinical diagnosis managed with rest and follow-up, separate from the CT decision.
Why avoid CT in children when in doubt?
Radiation. A head CT delivers meaningful radiation to a developing brain, and the lifetime cancer risk, while small per scan, is real and cumulative. The whole point of PECARN is to reserve CT for children whose injury risk justifies the radiation. Observation is the alternative, not doing nothing.
What are signs of basilar skull fracture?
Raccoon eyes (bruising around the eyes), Battle sign (bruising behind the ear), blood or clear fluid from the nose or ears, and hemotympanum (blood behind the eardrum). These suggest a fracture at the skull base and are a predictor in the older-child list.
Can parents use this at home?
It is designed for emergency department use within 24 hours of injury, but informed parents can use it to understand the decision. Any concerning sign, worsening headache, repeated vomiting, unusual sleepiness, or seizure needs emergency evaluation regardless of what a checklist says. When in doubt, get checked.
What if the child vomits once, hours later?
Isolated vomiting is a predictor in the 2-and-older group, so it moves the child out of the very-low-risk category. In practice, many clinicians choose brief emergency department observation for a single vomit in an otherwise well child rather than immediate CT. The rule allows observation versus CT for exactly this situation.
Does PECARN apply to sports concussions on the field?
Not directly. Sideline concussion assessment uses different tools focused on symptoms and balance. PECARN answers whether a child already in the emergency department needs a CT. A concussed athlete still needs proper concussion protocol even with a reassuring PECARN result.