Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm





    Chief Complaint


    Organ System


    Patent Pending

    Pediatric NEXUS II Head CT Decision Instrument for Blunt Trauma

    Predicts need for head CT after pediatric blunt head injury, similar to PECARN.


    Use in patients <18 years old who have sustained blunt head trauma within the past 24 hours and in whom head CT is being considered. 

    Note: We recommend using PECARN over other pediatric head trauma rules, as it is the most widely validated (see Next Steps for details).

    When to Use
    Why Use

    Patients <18 years old who have sustained blunt head trauma within the past 24 hours and in whom head CT is being considered.

    • Only patients for whom the clinician was going to perform a head CT (regardless of the decision tool result) were included in the study.

    • May not have adequate sensitivity in patients with high GCS scores (14-15), as GCS scores were not reported.

    • Outcomes of those who did not have head CT performed based on clinical gestalt are not known.

    • The validation study included only 35% male patients, which is in stark contrast to previous studies that have found boys were more likely to present with head injuries (64.8%, 65%, and 62% of patients were male in CATCH, CHALICE, and PECARN respectively).

    • The study population was substantially older compared to those for previous decision instruments (11.9 years, versus 7.1 years in PECARN).

    • Because this study did not enroll patients who did not undergo head CT, no firm conclusions can be made regarding whether this decision instrument would have satisfactory sensitivity and/or reduce head CT imaging in ALL pediatric patients with head trauma.

    May safely reduce use of head CT imaging (derivation and validation showed 100% sensitivity for identifying patients requiring neurosurgical intervention, with subsequent reduction in head CT of 25% and 34%, respectively).


    Diagnostic Result:

    Please fill out required fields.

    Next Steps
    Creator Insights


    • In low risk populations, we would recommend using other externally validated tools to determine the necessity of head CT in pediatric blunt head trauma patients (i.e., PECARN).
    • Our recommendation for the PECARN Head Injury Algorithm is based partly on the fact that it enrolled the largest number of patients during its derivation and validation (33,785 in derivation cohort and 8,627 in the validation cohort). This compares to 22,772 enrolled in the original CHALICE study, 3,866 patients for the CATCH Rule, and 1,018 subjects enrolled in Pediatric NEXUS II Head CT instrument.
    • PECARN also has the highest negative predictive value (NPV) (100% and 99.95% for children <2 and ≥2 years-old, respectively). That said, the NPV of the CHALICE (99.8%) and CATCH (99.9%) rules are also excellent and present additional reasonable options.


    • Patients who do not meet criteria for imaging should always be counseled about the following:
    • Concussion and its symptoms.
    • Strict head injury return precautions (e.g. vomiting, somnolence/altered mental status).
    • Many still recommend a period of observation after head injury.


    • Patients who meet criteria for head CT may have intracerebral hemorrhage or they may not; however, if the criteria of the instrument are met, head CT is recommended.

    Critical Actions

    Remember, this decision instrument was only applied to a population of pediatric patients in which clinicians were intending on performing head CT. This may have eliminated a clinically “low risk” group of patients (i.e., GCS 15). Thus, applying this instrument to this population is not recommended.


    Selection of the appropriate criteria:



    Evidence of skull fracture

    Basilar: e.g. periorbital or periauricular ecchymoses, hemotympanum, drainage of clear fluid from ears or nose

    Depressed/diastatic: palpable step-off, stellate laceration from a point source, or any injury produced by an object striking a localized region of the skull (e.g. baseball bat, club, pool cue, golf ball, baseball, pipe)

    Scalp hematoma

    Injuries not involving calvarium (e.g. hematomas limited to the face/neck) are not considered scalp hematomas

    Neurologic deficit

    Any abnormal neurologic finding revealed by detailed exam, e.g. motor or sensory deficits (abnormal weakness/sensation in ≥1 extremity; cranial nerve abnormality (particularly II through XII); cerebellar abnormality as manifested by ataxia, dysmetria, dysdiadokinesis, or other impairment of cerebellar function (as determined by systematic testing of cerebellar function, including tests of ataxia and finger-nose-finger, heel-to-shin, and rapid alternating movements); gait abnormality or inability to walk normally due to inadequate strength, loss of balance, or ataxia; perform systematic testing of gait, including tandem and heel-to-toe walking, and Romberg testing); or any other impairment of neurologic function

    Abnormal level of alertness

    e.g. GCS ≤14; delayed or inappropriate response to external stimuli; excessive somnolence; disorientation to person, place, time, or events; inability to remember three objects at 5 mins; perseverating speech

    Abnormal behavior

    Any inappropriate action, e.g. excessive agitation, inconsolability, refusal to cooperate, lack of affective response to questions or events, violent activity

    Persistent vomiting

    Recurrent projectile or forceful emesis (>1 episode), either observed or by history, after trauma


    Any clotting impairment, e.g. hemophilia, secondary to medications (Coumadin, heparin, aspirin, etc), hepatic insufficiency

    Facts & Figures


    Criteria present

    Risk of significant intracranial injuries




    CT not necessary (100% sensitive for findings requiring neurosurgical intervention*)



    Consider CT

    *Death due to head injury, need for craniotomy, elevation of skull fracture, intubation related to head injury, or intracranial pressure monitoring, within 7 days of head injury.

    Evidence Appraisal

    Derivation Study (Oman 2006)

    • NEXUS II was a prospective, observational, multicenter trial in which patients who suffered blunt head trauma were undergoing a head CT.

    • An analysis was performed of the pediatric subgroup (age <18 years old) of the NEXUS II cohort.

    • The pediatric cohort enrolled 1,666 patients with 8.3% suffering an important intracranial injury (ICI), defined as requiring neurosurgical intervention (craniotomy, intracranial pressure monitoring, or mechanical ventilation).

    • Application of the study criteria was 98.6% sensitive for ICI (missing two cases); however, it was 100% sensitive for injuries requiring neurosurgical interventions.

      • The criteria truly only missed one patient as there was an error in assessment of one patient with scalp hematoma.

    • Application of the decision instrument would have decreased head CT usage by 25% in this study population.

    Validation Study (Gupta 2018)

    • This was a planned secondary analysis of patients <18 years old who sustained blunt head trauma and were undergoing head CT at an enrolling institution.

    • 1,018 patients were included in the analysis of which 2.7% required neurosurgical intervention and 4.8% sustained significant intracranial injuries.

    • Application of the study criteria was 100% sensitive for those who required neurosurgical intervention and 98% sensitive for those who sustained a significant intracranial injury.

    • Applying the decision instrument to this study population could have reduced head CT imaging by 34%.


    • Previous decision instruments have been studied to identify pediatric blunt head trauma patients who can be identified as low risk and defer head CT (CATCH, CHALICE, PECARN).

    • PECARN was found to have the highest sensitivity in a prospective cohort study in 2017; however, NEXUS II was not analyzed in this study (Babl 2017).

    • The age of the study population was substantially older (11.9 years) compared to PECARN (7.1 years).

    • Application of PECARN to pediatric blunt head trauma patients has been shown to decrease head CT performed by 9-17% (Dayan 2017, Jennings 2017, Nigrovic 2015).

    Overall, the derivation and validation studies are very well performed. The critique for practice implementation is in regard to the safety of the gestalt of the provider in determining who did and did not need a head CT. As previously mentioned, only those who underwent head CT were included in the NEXUS II study and analysis. Outcomes and data on pediatric blunt head trauma patients who did not receive head CT are not known. If data were available to analyze this population and clinician gestalt was determined to have satisfactory sensitivity, NEXUS II may be implemented in clinical practice more widely.


    Dr. William R. Mower

    About the Creator

    William R. Mower, MD, PhD, is a physician at the UCLA Emergency Medical Center. He is also a professor of medicine at the University of California Geffen School of Medicine. Dr. Mower’s primary research is focused on computed tomography and diagnostic radiology.

    To view Dr. William R. Mower's publications, visit PubMed

    Content Contributors
    Reviewed By
    About the Creator
    Dr. William R. Mower
    Content Contributors
    Reviewed By