Have you ever looked at your handy ultrasound and wondered: “What else can I scan with this?” Certainly, over the past ~2 decades, our point of care ultrasound has evolved into an indispensable asset. When used correctly, it is a very powerful tool that helps us expedite care and augment our physical exam. We use it to assess Chest Pain. We use it to answer clinical questions like is there Appendicitis, Intussusception, Testicular Torsion, Cholelithiasis, or Nephrolithiasis present in this patient? Many of these applications were not even imagined early on in this evolution. Perhaps in the coming years we will be reaching for the ultrasound to help answer even more questions. Let us consider another potential application – Ultrasound for Head Injury:

Head Injury in the Very Young

• We all are aware of the benefits and application of the PECARN Low Risk Head Injury guideline. [Kuppermann; 2009]
• The very young, however, can still be problematic even while fitting the “low risk” category for PECARN.

• Children < 3 months of age are particularly challenging.
  • Have thinner skull.
  • Have limited ability to protect themselves.
  • Have limited ability to communicate with us.
  • Observation period may not detect subtle changes in behavior.
• PECARN mentions these limitations as reasons to have lower threshold for imaging in the very young.

• The current standard for imaging is the Head CT, which introduces need to weigh:
  • Risk of Radiation,
  • Risk of Transport to Radiology Suite,
  • Risk of potential Sedation, and
  • Additional Cost.
• Additionally, let us not absentmindedly assume everyone has easy access to a Head CT… many children need care in regions that do not… or some patients may bee too critically ill to send to a CT scanner on the other side of the hospital.

Ultrasound for Head Injury

Wouldn’t it be great it we could just avoid the issue of Head CT and still mitigate our concerns for occult head injury?? The NICU uses ultrasound to evaluate extremely young infants with intracranial injuries including hemorrhages. [Orman, 2015; Soetaert, 2009] Does ultrasound have a role for our patients in the ED?

The simple answer is… yes… and no… or at least not yet. (yup, nothing is that simple.)

Skull Fractures

• POC ultrasound has been shown to be useful and reliable at diagnosing skull fractures. [Choi, 2018; Rabiner, 2013]
  • Reported Sensitivities range from 76.9 – 100% [Choi, 2018]
  • Reported Specificities range from 94 – 100% [Choi, 2018]

• Ultrasound results are dependent upon the operator, and imaging a small infant can be even more challenging.
  • Small interface surface between probe and target.
  • Hematoma or underlying fracture may make application of probe painful and limit child’s cooperation.
  • Skull suture lines can be confounding.
    • Knowledge of suture anatomy is required. [Parri, 2018; Choi, 2018; Rabiner, 2013]R
      • Irregular, jagged, displaced, or asymmetric findings are more consistent with fracture pattern.
      • Sutures should be continuous with a fontanelle. [Rabiner, 2013]
      • Imaging the contralateral aspect of the skull may help distinguish normal suture from fracture as well.
    • This is also true for Head CT imaging.

• Requires very cautious and meticulous scanning.
  • 3 regions where fractures have been missed in studies:
    • Supraorbital area
    • Lower Occipital Area
    • Region Adjacent to Hematoma (often the fracture is beneath the hematoma, but it may be near it as well)
  • Using a smaller probe and a water-filled glove (stand-off pad) can help improve scanning success in these regions.
  • Additional attention to these regions is recommended. [Parri, 2018; Choi, 2018]

• Point of Care Ultrasound can identify the presence and type of skull fractures. [Parri, 2018]
  • Isolated, simple, linear skull fractures often do not require intervention.
  • Depressed or complicated skull fractures may require intervention and POC U/S may help in expediting consultation.

Intracranial Hemorrhage

• Transfontanelle Ultrasound (TFUS) is able to evaluate intracranial structures and injury in infants. [Orman, 2015; Trenchs, 2008]
  • It does require a large enough fontanelle to adequately visualize all of the underlying structures. [Trenchs, 2008]
    • This varies with age and individual patients.
    • Anterior Fontanelle can close anytime between the 4th and 26th month of life.
  • Dependent upon operator!

• Limited Studies exist, but do show some promising results:
  • Trenchs, et al. [Trenchs, 2008]
    • Evaluated 123 infants (<13 months) who had a diagnosed linear skull fracture after minor head injury.
    • Demonstrated that Transfontanelle U/S, performed by radiologists, was useful for evaluating for intracranial injuries and, potentially, avoiding CT imaging.
    • Noted that TFUS has limited ability to evaluate the areas closer to the convexity of the skull.
  • McCormick, et al. [McCormick, 2017]
    • Evaluated children < 1 year of age – only 12 patients (4 with ICH an 8 Controls).
    • Found that POC U/S could identify Intracranial Hemorrhage, but that it was operational dependent.
    • Small sample size and wide confidence intervals limit the ability to draw useful conclusions of true sensitivity and specificity.

Moral of the Morsel

• Don’t get too excited (yet)! I know you love your Ultrasound, but right now, Cranial U/S is likely better at ruling-in fractures and hemorrhage, rather than ruling them out. More studies need to be done.
• Perfect your skills! Just because we are getting older (at least I know I am), doesn’t mean that there aren’t new skills for us to learn. Keep improving your U/S skills!
• Augment Observation? If your plan was to observe the child after a minor head injury, because the patient was low-risk, but not no-risk, then (perhaps) consider using your U/S skills (once perfected) to augment that observation period (especially, if finding a skull fracture would change your plan!).
• Window into the Brain! Your patient may be too unstable to go to CT (or you may not have access to a CT)… use that fontanelle to take a peak inside and expedite care!

References