PECARN head injury rule: the two age trees and their findings
The PECARN head injury rule uses two trees, one for children under 2 and one for children aged 2 to 17. Each tree has a group of high-risk factors and a group of intermediate factors. The calculator checks the high-risk group first, then the intermediate group, and returns the first group that has a finding present, or neither. Under 2, the high-risk factors are GCS 14 or less, altered mental status and a palpable skull fracture. From age 2, the third high-risk factor is signs of a basilar skull fracture instead.
This page doesn't give disposition advice. It shows which findings each tree uses and how they're checked. What the result means for imaging depends on the clinical context.
Not a medical device. Not a diagnosis or dosing recommendation.
What is the PECARN head injury rule?
The PECARN head injury rule (also called the PECARN head CT rule or the PECARN pediatric head trauma rule) comes from the PECARN research network. It was published by Nathan Kuppermann, James F. Holmes, Peter S. Dayan and colleagues in The Lancet in 2009.
The 2009 abstract says the authors' aim "was to identify children at very low risk of clinically-important traumatic brain injuries (ciTBI) for whom CT might be unnecessary." They built separate prediction rules for younger and older children.
Magent's calculator returns a field named risk_tier along with three true/false imaging fields. This page explains which findings drive those fields. It doesn't say what any result means for imaging.
The PECARN logic
tree = (age < 2) ? under-2 tree : 2-to-17 tree
if any high-risk factor in that tree -> high-risk group matched
else if any intermediate factor in tree -> intermediate group matched
else -> neither group matchedExact expression the calculator uses:
high if any age-applicable high-risk factor, else intermediate if any age-applicable intermediate factor, else low; lt_2 tree if age < 2, ge_2 tree if age 2-17There are no points. The tree is decided by age, and a high-risk finding always takes priority over an intermediate one.
Under-2 tree (ages 0 and 1)
| Group | Finding | Input |
|---|---|---|
| High-risk | GCS 14 or less | gcs_le_14 |
| High-risk | Altered mental status | altered_mental_status |
| High-risk | Palpable skull fracture | palpable_skull_fracture |
| Intermediate | Occipital, parietal or temporal scalp hematoma (not frontal) | nonfrontal_scalp_hematoma |
| Intermediate | Loss of consciousness 5 seconds or more | loc_ge_5_seconds |
| Intermediate | Not acting normally per parent | not_acting_normally |
| Intermediate | Severe mechanism of injury | severe_mechanism |
2-to-17 tree
| Group | Finding | Input |
|---|---|---|
| High-risk | GCS 14 or less | gcs_le_14 |
| High-risk | Altered mental status | altered_mental_status |
| High-risk | Signs of basilar skull fracture | signs_basilar_skull_fracture |
| Intermediate | History of loss of consciousness | history_of_loc |
| Intermediate | History of vomiting | history_of_vomiting |
| Intermediate | Severe headache | severe_headache |
| Intermediate | Severe mechanism of injury | severe_mechanism |
How to apply the rule
- Pick the tree. Age 0 or 1: the under-2 tree. Age 2 to 17: the 2-to-17 tree. Age 18 isn't accepted.
- Check the high-risk group for that tree. Any finding present: the high-risk group is matched, and the intermediate group isn't checked.
- Otherwise check the intermediate group. Any finding present: the intermediate group is matched.
- Otherwise neither group is matched.
Findings from the other tree don't count
The calculator asks for every finding from both trees, but the calculator uses just the age-applicable tree's findings. A 1-year-old with vomiting, severe headache and signs of basilar skull fracture matches neither group, because those findings belong to the 2-to-17 tree.
What counts as altered mental status and severe mechanism
Magent's record gives these definitions. Altered mental status is "agitation, somnolence, repetitive questioning, or slow response." Severe mechanism is a motor vehicle crash with ejection, rollover or death of another passenger; a pedestrian or bicyclist without a helmet struck by a motorized vehicle; a fall of more than 3 feet (under 2) or more than 5 feet (2 and older); or the head struck by a high-impact object. The caller decides both; Magent doesn't classify the mechanism or take a fall height.
What the calculator returns
Magent's calculator returns the age and tree it used, risk_tier, three true/false imaging fields and a row for each age-applicable finding. This page doesn't interpret the tier or the imaging fields.
Worked examples
These use Magent's own expected values for the calculator. Unless stated, every finding is false.
Example 1: age 1, nothing present
- Age 1 → under-2 tree.
- No high-risk or intermediate finding.
- Neither group matched.
Example 2: age 1, palpable skull fracture
- Under-2 tree.
- Palpable skull fracture is a high-risk finding.
- High-risk group matched.
Example 3: age 1, non-frontal scalp hematoma
- Under-2 tree.
- No high-risk finding.
- Non-frontal scalp hematoma is an intermediate finding.
- Intermediate group matched.
Example 4: age 10, GCS 14 or less plus vomiting
- 2-to-17 tree.
- GCS 14 or less is high-risk.
- Vomiting is intermediate, but the high-risk group takes priority.
- High-risk group matched.
Example 5: age 2
- Age 2 uses the 2-to-17 tree, not the under-2 tree.
PECARN reference values
These are Magent's expected values for the calculator.
At age 1 (the under-2 tree), no finding matches neither group. GCS 14 or less, a palpable skull fracture or altered mental status matches the high-risk group. A non-frontal scalp hematoma, LOC of 5 s or more, a severe mechanism or not acting normally matches the intermediate group. Findings from the 2–17 tree (LOC, vomiting, headache, basilar signs) match neither group at age 1.
At age 10 (the 2–17 tree), no finding matches neither group. GCS 14 or less, signs of basilar skull fracture or altered mental status matches the high-risk group, and so does GCS 14 or less with vomiting. History of LOC, history of vomiting, severe headache or a severe mechanism matches the intermediate group.
With no findings, age 0 uses the under-2 tree, and ages 2 and 17 use the 2–17 tree; all three match neither group.
History of the PECARN head injury rule
The rule comes from Nathan Kuppermann, James F. Holmes, Peter S. Dayan, John D. Hoyle, Shireen M. Atabaki and colleagues, Identification of children at very low risk of clinically-important brain injuries after head trauma: a prospective cohort study, The Lancet, 2009 (volume 374, issue 9696, pages 1160–1170).
The abstract starts from a concern: "CT imaging of head-injured children has risks of radiation-induced malignancy." The researchers "enrolled patients younger than 18 years presenting within 24 h of head trauma with Glasgow Coma Scale scores of 14-15 in 25 North American emergency departments."
They defined a clinically important injury as "death from traumatic brain injury, neurosurgery, intubation >24 h, or hospital admission >or=2 nights." In total they "enrolled and analysed 42 412 children."
The abstract lists each rule's very-low-risk findings. For under 2: "normal mental status, no scalp haematoma except frontal, no loss of consciousness or loss of consciousness for less than 5 s, non-severe injury mechanism, no palpable skull fracture, and acting normally according to the parents." For 2 and older: "normal mental status, no loss of consciousness, no vomiting, non-severe injury mechanism, no signs of basilar skull fracture, and no severe headache." Those are the same findings Magent's two trees use. The abstract doesn't describe the split into high-risk and intermediate groups; that comes from Magent's record and code.
When it's used
The 2009 study enrolled children under 18 seen within 24 hours of head trauma with a GCS of 14 or 15. Magent's record describes the calculator as applying after blunt head trauma in children aged 0 to 17.
Where it's used
The study took place in 25 North American emergency departments.
Who uses it
In the 2009 study, the findings were recorded for children seen in emergency departments after head trauma.
Limits of the calculation
- It sorts findings into groups. It doesn't diagnose a brain injury or examine a child.
- Every finding is the caller's call, including GCS 14 or less (as a yes/no answer), altered mental status and severe mechanism.
- Findings from the other age tree are ignored.
- It's the Kuppermann 2009 head rule. It isn't the Canadian CT Head Rule, CATCH, CHALICE, NEXUS or the other PECARN rules.
- This page doesn't say what any group or imaging field means for a child.
Clinical decisions belong to a qualified clinician who knows the patient.
How it differs from related calculators
- Canadian CT Head Rule is for adults with minor head injury, with its own seven findings.
- Glasgow Coma Scale gives the 3–15 number. PECARN takes a yes/no answer for GCS 14 or less instead.
Glossary
- ciTBI: clinically important traumatic brain injury, as defined in the 2009 study.
- Basilar skull fracture: a fracture at the base of the skull.
- Scalp hematoma: a collection of blood under the scalp; the under-2 tree counts non-frontal ones and not frontal ones.
- LOC: loss of consciousness.
- GCS: Glasgow Coma Scale, scored 3 to 15.
- PECARN: Pediatric Emergency Care Applied Research Network.
Common mistakes
- Using the wrong tree at age 2. Age 2 uses the 2-to-17 tree.
- Counting findings from the other tree. Vomiting doesn't count under 2; palpable skull fracture doesn't count from 2.
- Counting a frontal scalp hematoma. The under-2 finding is a non-frontal hematoma; frontal doesn't count.
- Entering a GCS number. The input is yes/no for GCS 14 or less.
- Treating the groups as a score. There are no points; the high-risk group takes priority.
Source
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;374(9696):1160-1170. DOI: 10.1016/S0140-6736(09)61558-0
Frequently asked questions
What are the PECARN head injury criteria?
Under 2: GCS 14 or less, altered mental status, palpable skull fracture, non-frontal scalp hematoma, loss of consciousness 5 seconds or more, not acting normally, severe mechanism. From 2 to 17: GCS 14 or less, altered mental status, signs of basilar skull fracture, history of loss of consciousness, vomiting, severe headache, severe mechanism.
When does PECARN say a head CT is needed?
This page doesn't give disposition advice. It shows which finding group the calculator matches.
What counts as a severe mechanism in PECARN?
Per Magent's record: a crash with ejection, rollover or death of another passenger; an unhelmeted pedestrian or bicyclist hit by a motorized vehicle; a fall over 3 feet (under 2) or 5 feet (2 and older); or a high-impact blow to the head.
Which PECARN tree does a 2-year-old use?
The 2-to-17 tree.
Who developed the PECARN head injury rule?
Nathan Kuppermann and colleagues, in a 2009 paper in The Lancet.