SGEM#124: Ultrasound for Skull Fractures – Little Bones - The Skeptics Guide to Emergency Medicine

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Date: June 11th, 2015

Guest Skeptic: Dr. Greg Hall is Director of EM Ultrasound at the Brantford General Hospital in Brantford Ontario and Assistant Clinical Professor at McMaster University. He is Vice President of the Canadian Emergency Ultrasound Society, co-author of Point-of-care Ultrasound for Emergency Physicians, co-creator of the EDE 2 Course: Advanced Emergency Department Echo, and director of the EDE 3 Course, a leading edge POCUS workshop.

Case: An 18-month-old male presents to your small emergency department having a witnessed fall off a couch and hit his head on a hardwood floor. He threw up once and cried immediately at the scene. There was no loss of consciousness.

The parents are concerned about a serious head injury, particularly with the large hematoma, but understandably are not thrilled with the idea of the radiation exposure of a CT, need for sedation, and transport to another centre for the CT scan.

In the emergency department he is alert with a Glasgow Coma Scale of 15 and has no neurological deficits. Remembering your PECARN pediatric CT decision rules after listening to SGEM#112 with Dr. Anthony Crocco, you note that for children less than two years old a CT of the head is recommended if Glasgow Coma Scale<15, altered mental status, or palpable skull fracture. You would also consider a CT if non-frontal scalp hematoma, loss of consciousness greater than five seconds, severe mechanism, or abnormal activity.

This child looks great except for a large frontal hematoma and you want to be able to send him home but you know that the presence of a skull fracture increases the risk of an associated intracranial injury.

Honesty being the best policy, you acknowledge your lack of confidence in your ability to palpate a skull fracture and that forehead is kind of swollen.

Dr. Greg Hall

Background: Point of care ultrasound (POCUS) is becoming a popular method for detecting various types of fractures. It is fast, can be done on less stable patients you don’t want leaving the department, can be directed to the area of injury, and can be repeated, particularly when fracture reduction is required.

Ultrasound has been found to have good accuracy when performed by clinicians for various fractures (Weinberg et al Injury 2010) POCUS has been found to be equal or superior to plain films and even bone scans involving fractures of some flat bones like the sternum (Jin et al J Ultrasound Med 2006 and You et al J Clin Ultrasound)

Head injuries are a common presentation in children and the push to reduce exposure to ionizing radiation in young brains is greater than ever. Decision rules like the PECARN CT Head rules help reduce the number of CT scans done on minor head injury patients but the presence of skull fractures is known to increase the risk of an intracranial injury by over four times.

Close observation or CT is going to be a consideration in these fracture patients. Finding fractures with skull X-rays is a problem as they are difficult to interpret and still miss a number of fractures.

The clinical exam is not accurate either for skull fracture as this study demonstrates with 5% found in the very low pretest probability group and 33% found in the low to moderate group.

Thus it makes sense to consider the use of ultrasound that has no ionizing radiation, is well tolerated in children, and is not technically challenging to perform.

There have been several other studies now looking at using ultrasound for pediatric skull fractures. Sensitivities range from 82% to 100% and specificity from 94-100% (Weinberg et al Injury 2010, Riera and Chen Paediatr Emerg Care 2012 and Parri et al J Emerg Med 2013).

Clinical Question: Is ultrasound in the emergency department useful to rule-in or rule-out skull fractures in children?

Reference: Rabiner JE et al. Accuracy of point-of-care ultrasound for diagnosis of skull fractures in children. Pedatrics 2013

Population: Patients 21 years old or younger presenting to the emergency department with suspected skull fracture undergoing CT scan
- Excluded patients presenting with completed radiologic studies, a confirmed skull fracture, an open fracture, or if urgent intervention was required.
Intervention: Point of care ultrasound in the emergency department
- 60-minute training session for the EM physicians (30-minute didactic session to learn how to use ultrasound to evaluate the skull for fracture and a 30-minute hands-on practical session)
Comparison: CT scan
Outcome: Test characteristics (Sensitivity, specificity, PPV, NPV, +LR and -LR)

Authors’ Conclusions: Clinicians with focused ultrasound training were able to diagnose skull fractures in children with high specificity.

Quality Checklist for Diagnostic Studies:

The clinical problem is well defined. Yes Comments: Head trauma is a common occurrence in children and often clinicians are wondering about the diagnostic possibility of skull fractures. Ultrasound, if found to be useful, can help modify the radiation exposure to children who are often investigated with radiography or CT scans.
The study population represents the target population that would normally be tested for the condition (ie no spectrum bias) Yes
The study population included or focused on those in the ED Yes
The study patients were recruited consecutively (ie no selection bias) No
The diagnostic evaluation was sufficiently comprehensive and applied equally to all patients (ie no evidence of verification bias) Yes
All diagnostic criteria were explicit, valid and reproducible (ie no incorporation bias) Yes
The reference standard was appropriate (id no imperfect gold-standard bias) Yes
All undiagnosed patients underwent sufficiently long and comprehensive follow-up (ie no double gold-standard bias) Yes
The likelihood ratio(s) of the test(s) in question is presented or can be calculated from the information provided Yes
The precision of the measure of diagnostic performance is satisfactory Yes

Key Results: Point-of-care ultrasound was performed by 17 clinicians. There were 69 children under the age of 21years old with suspected skull fractures. The patients’ mean age was 6.4 years. The prevalence of fracture was 12% (8/69).

The test characteristics for detecting skull fractures were reported with 95% confidence intervals. More information on how to calculate these numbers can be found on MedCal.net.

Sensitivity 88% (53-98%) and Specificity 97% (89-99%)

PPV 0.78 (0.45- 0.94) and NPV 0.98 (0.91-1.0)

+LR 26.7 (6.7-106.9) and -LR 0.13 (0.02-0.81)

Overall this is a well-performed study on an important topic. More and more we are trying to limit the radiation exposure in children with closed head injuries. Point-of-care ultrasound offers the availability of quick, radiation- free results.

The results of this study are somewhat limited by the small number of patients included, a limitation that is evident from the wide confidence intervals. Another limitation is the sample used was one of convenience and not consecutive.

However, this is the largest single study looking at this topic. They used clinicians with one-hour focused training in skull fracture scanning and a technique of only scanning over the hematoma region.

Their single false negative patient (missed fracture) had a fracture adjacent to the hematoma so using a better technique of scanning on and around a hematoma would have likely discovered this fracture. The authors describe the patient with the missed fracture or false negative as requiring observation only and no specific treatment.

The first false positive was performed by a novice but over-read as negative by the senior clinician suggesting that training may be important to accuracy. The second false positive was called as a positive by both physicians reading the scan and negative on CT.

However, with small, non-depressed fractures, CT is not 100% sensitive either as demonstrated in the studies of other fracture areas. Thus this patient may have had a true positive on ultrasound and false negative on CT.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: Agree with the authors’ conclusions that emergency physicians with 60 minute ultrasound training were able to diagnose skull fractures in children with high specificity.

SGEM Bottom Line: Ultrasound is a useful adjunct for detecting skull fractures and further risk stratifying minor head injuries when used along with a clinical decision rule like PECARN. However serious intracranial injuries can occur without fracture and the sensitivity of ultrasound for fracture is not yet sufficient to use it as the sole method for detecting injury and making discharge decisions.

Case Resolution: You could order a skull Xray but you know they are hard to interpret, involve some radiation, will miss a significant number of fractures, and don’t provide any information about intracranial injury. Instead you decide to use your department’s portable ultrasound machine to look for a fracture and combine this with your clinical decision rules.

With Mom holding her son in her lap, you gently scan over and around the region of the frontal hematoma. There is no fracture visible so, along with PECARN rule support, you are happy to observe the child for a few hours in the ED and send him home with clear discharge instructions for the parents. They are reassured by your examination, seeing their son’s intact skull on the ultrasound and are content to avoid doing a CT unless his clinical picture changes later.

Clinically Application: Point-of-care ultrasound, in the hands of competent physicians, appears to be a viable option to rule-in and rule- out skull fractures in children.

One concern, from a clinical standpoint, is that often children with enough findings to merit concern about a skull fracture, have enough clinical findings to warrant a CT scan to rule-out intra-cranial pathology.

Also, the incidence of pathology below a skull fracture in children is high, so finding one on ultrasound may merit further investigation with CT scanning. Judicious use of radiation is encouraged, as there is evolving evidence of the long-term risks to mortality and development for children exposed to ionizing radiation.

What Do I Tell My Patient? We can use an ultrasound device to check and see if your son has a skull fracture. This can help me decide if he is at risk of having a more serious injury and needs to get a CT scan.

Keener Kontest: Last weeks winner was Dr. Garreth Debiegun from Tufts University. He knew Wong Baker is the name of a validated pain scales using faces to assess pain in children.

Listen to the podcast for this weeks keener question. If you know the answer send an email to TheSGEM@gmail.com with “keener” in the subject line. The first correct response will win a cool skeptical prize.