# Pediatric Head Trauma and the PECARN Rule
## Epidemiology
### Overview
Head trauma is the leading cause of death and disability in children. Traumatic brain injury accounts for approximately 500,000 pediatric ED visits annually in the United States. The vast majority are minor (GCS 14 to 15), and clinically important TBI occurs in less than 1 percent. The risk of clinically important TBI varies by age, mechanism, and clinical findings. The central challenge is balancing the radiation risk of CT scanning against the possibility of missing an intracranial injury.
### CT Radiation Concerns in Children
Children are more radiosensitive than adults because of their rapidly dividing cells and longer life expectancy, which provides more time for radiation-induced cancers to develop. A single head CT in a child carries an estimated 1 in 1,000 to 1 in 5,000 lifetime cancer risk, with the risk highest in the youngest children. The goal is to minimize unnecessary CTs while ensuring that clinically significant injuries are not missed.
## PECARN Pediatric Head Injury Decision Rules
### Overview
The PECARN study is the largest pediatric head injury study ever conducted, enrolling 42,412 children across 25 emergency departments. It produced two separate algorithms, one for children under 2 years and one for children 2 years and older, designed to identify those at very low risk for clinically important TBI (ciTBI) who do not need CT. Clinically important TBI is defined as death, neurosurgical intervention, intubation for more than 24 hours, or hospitalization for 2 or more nights.
### PECARN Rule: Children Under 2 Years
An infant or toddler under 2 years is at very low risk (CT not recommended) when all of the following are present: GCS of 15, no palpable skull fracture, normal mental status (acting normally per the parent), no loss of consciousness (or LOC less than 5 seconds), a non-severe mechanism, and no scalp hematoma except frontal (frontal hematomas carry lower risk).
The intermediate-risk group has an isolated finding such as a non-frontal scalp hematoma, LOC of 5 seconds or longer, not acting normally, or a severe mechanism. The ciTBI risk in this group is 0.9 percent, and the decision between observation and CT is left to physician judgment. Shared decision-making is recommended in this group but is inconsistently applied, with some physicians choosing to CT all intermediate-risk patients rather than observe.
The higher-risk group, where CT is recommended, includes children with a GCS below 15, altered mental status, or a palpable skull fracture. The ciTBI risk is 4.4 percent.
### PECARN Rule: Children 2 Years and Older
A child 2 years or older is at very low risk (CT not recommended) when all of the following are present: GCS of 15, no signs of basilar skull fracture, normal mental status, no loss of consciousness, no vomiting, a non-severe mechanism, and no severe headache.
The intermediate-risk group has an isolated finding of LOC, vomiting, severe headache, or a severe mechanism, with a ciTBI risk of 0.9 percent. The higher-risk group (CT recommended) includes children with a GCS below 15, altered mental status, or signs of basilar skull fracture, with a ciTBI risk of 4.3 percent.
### Severe Mechanisms (per PECARN)
Severe mechanisms include motor vehicle collision with patient ejection, death of another passenger, or rollover; pedestrian or bicyclist without a helmet struck by a motorized vehicle; a fall of more than 3 feet for children under 2 years or more than 5 feet for those 2 years and older; and the head being struck by a high-impact object.
### Performance
The sensitivity for ciTBI is 100 percent in the very low-risk group for children under 2 years and 96.8 percent for children 2 years and older. The negative predictive value is 99.9 percent. Application of the PECARN rule reduces CT utilization by approximately 25 to 30 percent.
## Observation Strategy for Intermediate-Risk Children
### When to Observe vs. CT
The observation period is 4 to 6 hours in the ED with serial neurologic assessments. Factors favoring observation include a single isolated intermediate-risk finding, physician experience suggesting low concern, improving symptoms during the observation period, parent preference (as part of shared decision-making), and the availability of reliable follow-up. Factors favoring CT include multiple intermediate-risk findings (each additional finding increases risk), worsening symptoms during observation, very young age (under 3 months, given the higher risk of occult injury), physician clinical concern, and unreliable follow-up or caregiver inability to observe the child at home.
### Serial Assessment
Neurologic checks should be performed every 30 to 60 minutes, evaluating GCS, pupil reactivity, mental status, and new symptoms. If the patient worsens, CT should be obtained. If the patient improves over 4 to 6 hours with normal repeated examinations, discharge with head injury precautions is safe.
## Skull Fractures in Children
### Types
Linear skull fractures are the most common type and are often non-operative, though they may cross vascular structures such as the middle meningeal artery and cause an epidural hematoma. Depressed skull fractures that are depressed more than one table width may require surgical elevation. Basilar skull fractures present with clinical signs including raccoon eyes, Battle sign, hemotympanum, CSF otorrhea or rhinorrhea, and cranial nerve palsies (with the seventh nerve most commonly affected). Growing skull fractures (leptomeningeal cysts) are unique to children under 3 years and involve a dural tear with herniation of the arachnoid through the fracture, causing progressive fracture widening that requires surgical repair.
### Palpable Skull Fracture in Infants
Soft, fluctuant scalp swelling that crosses suture lines represents a subgaleal hemorrhage, which can be significant in infants. A palpable step-off or crepitus indicates a fracture. In the PECARN algorithm for children under 2 years, a palpable skull fracture is a high-risk finding that warrants CT.
## Intracranial Hemorrhage Patterns
### Epidural Hematoma (EDH)
An epidural hematoma forms between the skull and the dura, typically from middle meningeal artery bleeding associated with a temporal bone fracture. On CT, it appears as a biconvex or lenticular hyperdense collection that does not cross suture lines. The classic presentation is a "lucid interval" with initial loss of consciousness, brief improvement, and then rapid deterioration from herniation. It is a surgical emergency when large or when neurologic decline occurs.
### Subdural Hematoma (SDH)
A subdural hematoma forms between the dura and the arachnoid from tearing of bridging veins. On CT, it appears as a crescent-shaped collection that crosses suture lines. In infants without a significant mechanism, it is highly concerning for non-accidental trauma. Acute subdural hematomas are hyperdense on CT, chronic subdurals are hypodense, and mixed collections show both densities.
### Subarachnoid Hemorrhage
Traumatic subarachnoid hemorrhage is common in moderate to severe TBI and typically follows the cortical contours.
### Intraparenchymal Hemorrhage/Contusion
Contusions result from coup (direct impact) and contrecoup (opposite side) injuries and are common in the frontal and temporal poles.
## Non-Accidental Trauma (NAT)
### Red Flags
Red flags for non-accidental trauma include a history inconsistent with the injury pattern or the child's developmental stage, a delay in seeking care, a changing or vague history, injuries in pre-ambulatory infants (under 6 months), bilateral or multiple subdural hematomas (especially of different ages), retinal hemorrhages (which are highly specific for abusive head trauma though not pathognomonic), and associated injuries such as posterior rib fractures, metaphyseal corner fractures, and multiple fractures in different stages of healing.
### Workup When NAT Is Suspected
The workup includes a skeletal survey for all children under 2 years with suspected abuse, a dilated fundoscopic examination for retinal hemorrhages, liver function tests (with AST or ALT above 80 U/L triggering an abdominal CT), lipase, urinalysis for hematuria suggesting renal injury, coagulation studies to exclude a bleeding diathesis, and a follow-up skeletal survey in 2 weeks to detect healing fractures not visible initially.
### Legal Obligations
Mandatory reporting is required in all jurisdictions, even when suspicion is uncertain. Child protective services and hospital social work should be contacted. Findings should be documented thoroughly with photographs when possible.
The PECARN Pediatric Head Injury Decision Algorithm displayed as a dual flowchart. Left flowchart for children under 2 years: begins with GCS assessment. If GCS less than 15 OR altered mental status OR palpable skull fracture → CT recommended (4.4% ciTBI risk). If GCS 15 and no skull fracture and normal mental status → assess for intermediate risk factors (non-frontal scalp hematoma, LOC 5 or more seconds, not acting normally per parent, severe mechanism). If any present → observation vs. CT (0.9% risk); if none present → CT not recommended (less than 0.02% risk). Right flowchart for children 2 years and older: same GCS assessment. If GCS less than 15 OR altered mental status OR basilar skull fracture signs → CT recommended (4.3% risk). If GCS 15 → assess for LOC, vomiting, severe headache, severe mechanism. If any → observation vs. CT (0.9% risk); if none → CT not recommended (less than 0.05% risk).
A CT scan comparison panel showing four types of intracranial hemorrhage. Panel 1: Epidural hematoma — biconvex (lens-shaped) hyperdense collection in the temporal region, with annotation showing it does NOT cross suture lines and is often associated with a temporal bone fracture. Panel 2: Subdural hematoma — crescent-shaped hyperdense collection along the convexity, crossing suture lines, conforming to the brain surface. Panel 3: Subarachnoid hemorrhage — hyperdense blood in the sulci and basal cisterns. Panel 4: Intraparenchymal contusion — focal hyperdense area within the brain parenchyma with surrounding edema. Each panel includes an arrow pointing to the key finding.
An infographic about non-accidental trauma (NAT) red flags in pediatric head injury. The center shows an infant with surrounding callout boxes highlighting: inconsistent history with injury mechanism, delay in seeking care, injuries in pre-ambulatory infants, bilateral subdural hematomas of different ages, retinal hemorrhages (shown as a fundoscopic image), posterior rib fractures and metaphyseal corner fractures (shown on skeletal survey X-ray). A checklist of required workup items is shown: skeletal survey, dilated fundoscopy, LFTs with lipase, UA, coagulation studies, mandatory reporting to CPS.
## Clinical Pearls
PECARN identifies children at very low risk for clinically important TBI with near-100 percent sensitivity and should be applied consistently to reduce unnecessary CTs. Multiple intermediate-risk factors increase risk additively, so a single isolated factor warrants observation, but multiple factors lower the threshold for CT. Observation for 4 to 6 hours with serial neurologic checks is a valid alternative to CT in intermediate-risk children, and this is where shared decision-making with parents is most important. Non-frontal scalp hematomas in infants under 2 years carry higher risk than frontal hematomas, and this specific distinction matters in the PECARN algorithm. Any intracranial injury in a pre-ambulatory infant (under 6 months) without a clear accidental mechanism warrants evaluation for non-accidental trauma. Bilateral subdural hematomas of different ages combined with retinal hemorrhages is highly concerning for abusive head trauma. Mandatory reporting of suspected child abuse is a legal obligation that should be made even when uncertain, as investigation is not the physician's role. The lucid interval in epidural hematoma is a classic but not universal presentation, and any patient with declining neurologic status needs emergent CT and neurosurgical consultation.
## References
- Kuppermann N, et al. Identification of children at very low risk of clinically-important brain injuries after head trauma: a prospective cohort study (PECARN). *Lancet*. 2009;374:1160-1170.
- Dayan PS, et al. Association of traumatic brain injuries with vomiting in children with blunt head trauma. *Ann Emerg Med*. 2014;63:657-665.
- Schonfeld D, et al. Pediatric Emergency Care Applied Research Network head injury clinical prediction rules for ciTBI — external validation. *Ann Emerg Med*. 2014;63:696-703.
- Christian CW, et al. Abusive head trauma in infants and children (AAP Committee on Child Abuse and Neglect). *Pediatrics*. 2009;123:1409-1411.
- Brenner DJ, et al. Computed tomography — an increasing source of radiation exposure. *NEJM*. 2007;357:2277-2284.