In a 2‑month‑old infant with head injury, what criteria determine whether a head CT scan is required?

Head CT Criteria for 2-Month-Old Infants with Head Injury

In a 2-month-old infant with head injury, use the PECARN criteria to determine CT necessity: infants at very low risk (GCS 15 with NO altered mental status, NO palpable skull fracture, NO nonfrontal scalp hematoma, NO loss of consciousness >5 seconds, NO severe mechanism of injury, and acting normally per parents) can safely forgo CT scanning. 111

Risk Stratification Algorithm

Very Low Risk - NO CT Required

The infant must meet ALL of the following criteria 11:

• GCS of 15
• Normal mental status (no altered consciousness)
• NO palpable skull fracture
• NO nonfrontal scalp hematoma (frontal hematomas alone are lower risk)
• NO loss of consciousness >5 seconds
• NO severe mechanism of injury (e.g., motor vehicle crash, fall >3 feet, struck by high-impact object)
• Acting normally per parents (feeding, interacting, consolable)

This combination has 100% sensitivity and 100% negative predictive value for clinically important traumatic brain injury, with risk <0.02%. 11 These criteria have been externally validated in over 4,000 infants under 2 years of age 1.

Intermediate Risk - Consider CT or Observation

The infant has GCS 15 and normal mental status but has ONE OR MORE of 11:

• Loss of consciousness >5 seconds
• Severe mechanism of injury
• Not acting normally per parent

Risk of significant injury: approximately 0.9% 1

CT may be considered instead of observation when:

• Parental preference for immediate imaging
• Multiple risk factors present
• Worsening symptoms during observation period
• Young infant where behavioral assessment is challenging 11

High Risk - CT Strongly Recommended

The infant has ANY of 11:

• GCS of 14 or less
• Other signs of altered mental status (lethargy, irritability that cannot be consoled)
• Palpable skull fracture

Risk of clinically important intracranial injury: approximately 4.4% 1

Critical Clinical Pearls

Scalp hematoma characteristics matter: Nonfrontal location significantly increases risk. Large, boggy hematomas (>3 cm) are particularly concerning and associated with higher TBI risk (OR = 3.67) 23.

Vomiting is a key predictor: Multiple episodes of vomiting increase both the likelihood of CT utilization and abnormal findings (OR: 3.73 for pathological CT) 24.

Clinical deterioration during observation: Any worsening of symptoms (increased irritability, decreased responsiveness, new vomiting) during ED observation mandates CT imaging (OR: 20.22 for pathological findings) 2.

Common Pitfalls to Avoid

Do not rely on skull radiographs - they miss up to 50% of intracranial injuries and are insufficient for trauma evaluation 11.

Do not assume all head trauma requires imaging - the vast majority (92.2%) of imaged young children have normal CT scans 2. Unnecessary CT exposes infants to radiation and often requires sedation.

Beware of delayed presentation - abnormal findings may appear hours after injury. When CT is not performed, provide clear return precautions and consider telephone follow-up 5.

Consider non-accidental trauma - in infants with concerning mechanisms (no witnessed trauma, inconsistent history, multiple injuries), maintain high suspicion. Bridging vein rupture and complex hemorrhage patterns are exceptional in minor accidental trauma 6.

Observation Protocol When CT Deferred

For very low-risk infants where CT is safely deferred 5:

• Minimum 4-6 hours of observation in ED or capable facility
• Serial neurological assessments every 1-2 hours
• Clear discharge instructions to parents about warning signs
• Telephone follow-up within 24 hours
• Immediate return for: persistent vomiting, worsening headache/irritability, seizures, decreased responsiveness, focal neurological signs