Pediatric NEXUS II Head CT Decision Instrument for Blunt Trauma

Why did you develop the Pediatric NEXUS II Head CT Decision Instrument for Blunt Trauma? Was there a particular clinical experience or patient encounter that inspired you to create this tool for clinicians?

The Pediatric NEXUS Head CT Decision Instrument for Blunt Trauma was developed as part of the NEXUS program to develop decision instruments that not only guide radiographic imaging of blunt trauma patients, but safely provide the greatest possible reductions in radiographic imaging. Our philosophy is based on the concept that diagnostic testing performed on patients who do not have disease, can only produce harm.

Using the NEXUS tools, including the Pediatric Head Imaging tool, requires the recognition of the “applicable cohort” of patients that are suitable for evaluation by the rule. The NEXUS rules are not intended to be applied to all blunt injury patients, but are instead targeted at cases where imaging is being contemplated due to concerns about injury. At this point, “low risk” NEXUS classification signifies that the risk of imaging (radiation induced lethal malignant transformation) exceeds the negligible risk of injury, and that imaging is contra-indicated. This means the NEXUS rules function as “one way” tools that provide guidance on when not to image. Using them to provide guidance on when to image (“two way” rules) is inappropriate and diminishes the efficacy of the rules.

Our deliberate efforts to develop one-way tools reflects the fact that clinicians are already very good at identifying patients who have sustained injuries, and that occult injuries are very rare. This concept is not only supported in the literature, but has been confirmed in each of our studies where we carefully followed unimaged blunt trauma patients to determine how frequently they sustained significant injuries. Over the years of our studies, we have yet to find a single case of significant occult missed injury. Such injuries are very rare and efforts to detect them are hazardous because the risk of lethal malignant transformation from increased imaging quickly exceeds any benefits. This is particularly important in pediatric patients who have a much greater life-time malignancy risk from ionizing radiation exposure.

Used properly, the NEXUS tools can only decrease imaging because they will never recommend imaging for patients that clinicians did not already intend to image. Numerous studies confirm the ability of the NEXUS tools to decrease imaging, and affirm their superiority over two-way tools.

What pearls, pitfalls and/or tips do you have for users of the Pediatric NEXUS II Head CT Decision Instrument for Blunt Trauma? Do you know of cases when it has been applied, interpreted, or used inappropriately?

Many decision tools, including the PECARN rule, are “two way” tools that provide guidance on when to image, as well as when not to image. These tools implicitly assume that occult injuries are common and that clinicians need guidance on when to image to ensure the reliable detection of occult injuries. The problem with this approach is that patients deemed low risk by clinicians, truly are low risk; occult injuries are rare. Application of a decision tool to these low risk patients will inevitably result in false-positive classification for some patients leading to an increase in unnecessary imaging and decreased efficacy of the rule. The Pediatric NEXUS II Head CT instrument should not be used as a two-way rule.

In addition, as with any decision tool, superficial evaluations can be problematic. Accurate classification requires careful assessments of the individual criterion, including careful neurological evaluation and focused examination of the head and face.

What recommendations do you have for doctors once they have applied the Pediatric NEXUS II Head CT Decision Instrument for Blunt Trauma? Are there any adjustments or updates you would make to the score based on new data or practice changes?

Clinicians who are experienced in evaluating blunt injury patients should feel comfortable and confident in using the Pediatric NEXUS II Head CT instrument as designed. Less experienced physicians, and those concerned about their ability to identify children with serious intracranial injuries may want to employ the NEXUS tool as a two-way rule, or use one of the existing validated two-way rules. While two-way approaches suffer from an impaired ability to decrease imaging, their high sensitivity implies that they can reliably identify children with significant intracranial injuries.

How do you use the Pediatric NEXUS II Head CT Decision Instrument for Blunt Trauma in your own clinical practice? Can you give an example of a scenario in which you use it?

Parents frequently request CT imaging for their children with minor head injuries. A careful evaluation of the child, in conjunction with an informative discussion on the manifestations of brain injury and the risks of imaging can typically resolve most parents' concerns. I employ the NEXUS rule in cases where I truly have concerns about potential injuries, and unless the rule provides a low risk classification, I proceed with imaging.

Any other research in the pipeline that you’re particularly excited about?

We are currently in the process of developing a NEXUS tool to guide abdominal/pelvic imaging of blunt trauma patients. Upon the completion of this project we will have completed the development of tools to guide core (head, neck, chest, abdomen and pelvis) CT imaging of blunt trauma patients. We are also focusing on ways to exploit artificial intelligence and neural networks to provide the next generation of clinical decision support tools.

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.