Intracranial Ultrasound for Head Trauma in Infants
Intracranial ultrasound does not have a significant role in the acute evaluation of head trauma in infants and should not be used as a primary imaging modality, as it lacks sensitivity for small subdural hematomas, posterior fossa hemorrhages, and other small extra-axial hemorrhages that can cause clinically important traumatic brain injury. 1
Primary Limitation of Ultrasound in Head Trauma
Even in infants with open fontanelles where brain ultrasound imaging is technically possible, ultrasound fails to reliably detect the intracranial injuries that matter most for morbidity and mortality. The American College of Radiology explicitly states that ultrasound lacks sensitivity for:
- Small subdural hematomas, particularly in the posterior fossa 1
- Other small extra-axial hemorrhages 1
- Intracranial injuries that can occur with or without skull fractures 1
While recent studies suggest ultrasound can detect calvarial (skull) fractures with sensitivity approaching CT 1, this capability is clinically insufficient because up to 50% of intracranial injuries in children occur without fractures 1. Detecting a fracture alone does not exclude life-threatening intracranial hemorrhage, and missing a fracture does not rule out dangerous bleeding.
The Appropriate Imaging Algorithm for Infants with Head Trauma
Very Low-Risk Infants (<2 years): No Imaging Needed
For infants under 2 years with ALL of the following PECARN criteria, imaging can be safely omitted with <0.02% risk of clinically important traumatic brain injury 2:
- Glasgow Coma Scale (GCS) of 15
- Normal mental status
- No palpable skull fracture
- No nonfrontal scalp hematoma
- Loss of consciousness ≤5 seconds (or none)
- No severe mechanism of injury
- Acting normally per parents 1, 2
High-Risk Infants (<2 years): CT Imaging Required
CT head without contrast is strongly recommended for infants with any of these features, as they carry approximately 4.4% risk of clinically important intracranial injury 1, 2:
Intermediate-Risk Infants (<2 years): CT vs. Observation
For infants with GCS 15, normal mental status, no palpable skull fracture, BUT with loss of consciousness >5 seconds, severe mechanism, or not acting normally per parent, CT may be considered versus careful clinical observation, as risk is approximately 0.9% 1, 2. CT should be obtained if:
- Parental preference for definitive imaging
- Multiple risk factors present
- Worsening symptoms during observation
- Young age where observational assessment is challenging 1
Why CT Remains the Gold Standard
CT provides rapid acquisition, excellent sensitivity for acute intracranial hemorrhage and fractures, requires no sedation, and can be performed in unstable patients 2, 3. This is critical because:
- Time to diagnosis directly impacts mortality in cases requiring neurosurgical intervention 3
- Delayed detection of epidural or subdural hematomas can lead to herniation and death 3
- CT identifies the 2-5% of injured infants who need neurosurgery 2
Critical Pitfalls to Avoid
Do not rely on ultrasound to exclude intracranial injury in infants with head trauma, even when the fontanelle is open. The American College of Radiology does not include ultrasound in any of their variant procedures for pediatric head trauma evaluation 1.
Do not assume that detecting a skull fracture on ultrasound is sufficient—the presence or absence of fracture does not reliably predict intracranial injury 1.
Do not obtain CT scans on very low-risk infants who meet all PECARN criteria, as this exposes them to unnecessary radiation without clinical benefit 2.
Limited Research Context
While small pilot studies suggest point-of-care ultrasound performed by trained physicians might detect some cases of traumatic intracranial hemorrhage 4, and one recent study showed 93% sensitivity for skull fractures and intracranial hemorrhage when performed by trained radiologists 5, these findings have not changed guideline recommendations. The ACR guidelines from 2020 remain clear that ultrasound "does not currently have a significant role in head trauma imaging" 1.