PECARN Head Injury (≥ 2y) Calculator

PECARN Head Injury (≥ 2y) Calculator for Pediatrics. The rule sorts children into three tiers rather than producing a number. Very-low-risk (all six predictors absent) carries a ciTBI risk below roughly 0.05 percent, so CT is not recommended. High-risk (altered mental status or palpable/clinical basilar skull fracture signs) carries about a 4.3 percent ciTBI risk, and CT is recommended. The intermediate group (any of LOC, vomiting, severe mechanism, or severe headache, without the high-risk features) carries roughly a 0.9 percent risk; here CT versus a period of structured observation is a judgment call informed by clinician experience, number and worsening of findings, parental preference, and ease of follow-up.

How this calculator works

This is the age-specific PECARN prediction rule for children 2 years and older presenting with blunt head trauma and a GCS of 14-15. It is not a summed numeric score but a hierarchical rule built on six binary predictors of clinically important traumatic brain injury (ciTBI): altered mental status (GCS 14 or agitation/somnolence/repetitive questioning/slow response), any signs of basilar skull fracture, history of loss of consciousness, vomiting, a severe injury mechanism, and severe headache. Presence of the two top-tier findings (altered mental status or basilar skull fracture signs) defines the high-risk group; the remaining four findings define an intermediate group; absence of all six defines the very-low-risk group.

When to use this calculator

Apply to otherwise healthy children aged 2 to under 18 years evaluated within 24 hours of blunt head trauma who have GCS 14-15. It is designed to safely identify who can skip a head CT and avoid ionizing radiation. Do not use it for penetrating trauma, known brain tumors, pre-existing neurological disorders, bleeding diatheses or anticoagulation, suspected non-accidental trauma, ventricular shunts, or when GCS is 13 or lower, all of whom warrant separate consideration and usually imaging.

Inputs used

  • Mental status
  • Loss of consciousness
  • Vomiting
  • Severe headache
  • Signs of basilar skull fracture
  • Severe mechanism

Clinical interpretation

The rule sorts children into three tiers rather than producing a number. Very-low-risk (all six predictors absent) carries a ciTBI risk below roughly 0.05 percent, so CT is not recommended. High-risk (altered mental status or palpable/clinical basilar skull fracture signs) carries about a 4.3 percent ciTBI risk, and CT is recommended. The intermediate group (any of LOC, vomiting, severe mechanism, or severe headache, without the high-risk features) carries roughly a 0.9 percent risk; here CT versus a period of structured observation is a judgment call informed by clinician experience, number and worsening of findings, parental preference, and ease of follow-up.

Worked example

A 6-year-old fell from standing height, had no loss of consciousness, is at his neurologic baseline with normal mental status, has no vomiting, no basilar skull fracture signs, and no severe headache. All six predictors are negative, placing him in the very-low-risk category. Given a ciTBI risk under 0.05 percent in this group, CT is not indicated and the child can be discharged with head-injury return precautions rather than irradiated.

Limitations and safety notes

In the validation cohort the ≥2y rule had 96.8 percent sensitivity (missing 2 of 63 ciTBIs), so it is marginally less perfect than the under-2 rule and a normal rule result does not fully exclude injury. Isolated severe headache or an isolated vomiting episode often lands children in the intermediate tier where the rule deliberately defers to clinician judgment rather than mandating action. It was neither derived nor validated for anticoagulated children, bleeding disorders, suspected abuse, shunts, or GCS below 14, and applying it outside GCS 14-15 blunt trauma is off-label. Observation before deciding on CT has been shown to reduce imaging without missing important injuries.

Frequently asked questions

Where does the age cutoff of 2 years come from?

PECARN derived two separate rules because injury patterns and the reliability of history and exam differ by age. The under-2 rule leans on scalp hematoma and parental report of acting normally, while the 2-and-older rule can incorporate self-reported symptoms like severe headache; a child is switched to the older rule at their second birthday.

What counts as a severe injury mechanism?

Examples include motor vehicle crashes with ejection, rollover, or a fatality; a pedestrian or unhelmeted cyclist struck by a vehicle; falls greater than about 5 feet for children 2 and older; or being struck by a high-impact object. A severe mechanism alone places a child in the intermediate group, not the high-risk group.

If a child is very-low-risk, is CT truly never needed?

CT is not routinely recommended, and the residual ciTBI risk is under 0.05 percent. Clinical judgment still governs; new or worsening symptoms during observation, or a concerning re-evaluation, can move a child out of the low-risk category and prompt imaging.

Does an intermediate result mean I must scan?

No. The intermediate tier (about 0.9 percent ciTBI risk) is where the rule intentionally offers a choice between CT and structured observation. Factors such as multiple versus isolated findings, symptom trajectory, clinician experience, distance from care, and parental preference should guide the decision.

Can it be used for anticoagulated children or suspected abuse?

No. These children were outside the derivation population. Anticoagulation, bleeding disorders, suspected non-accidental trauma, shunts, and known neurological conditions all fall outside the rule and generally warrant a lower threshold for imaging and specialist input.

References

  • Kuppermann N, Holmes JF, Dayan PS, et al. Identification of children at very low risk of clinically-important brain injuries after head trauma: a prospective cohort study. Lancet. 2009. PMID: 19758692.
  • Dayan PS, Holmes JF, Atabaki S, et al. Association of traumatic brain injuries with vomiting in children with blunt head trauma. Ann Emerg Med. 2014. PMID: 24559605.

Editorial review and citation methodology

Reviewed by the Quick Medical Calculator Editorial Team. Last reviewed: June 14, 2026. The review checks calculator inputs, intended population, interpretation, limitations, and source alignment.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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