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Ultrasound Assessment for Skull Fractures August 15, 2019

Posted by Andy Jagoda, MD in : Feature Update , trackback

The use of ultrasound at the point of care by emergency clinicians, as well as by other specialists, has become increasingly common over the last 25 years. Emergency POCUS can be used as a diagnostic test and also to visualize anatomy for procedural guidance. It allows the emergency clinician to rapidly rule in or rule out disease processes and guide ongoing investigation and management of patients in the ED.

Pediatric emergency ultrasound has been slower to progress than adult emergency ultrasound. However, the use of emergency ultrasound for pediatric patients has recently begun to formalize.

The pediatric patient is arguably more suited for emergency ultrasound than the adult patient. Children generally have a smaller body habitus than adults and, therefore, less tissue for the ultrasound beams to penetrate. This often leads to clearer images of the different organ systems, which should yield better diagnostic accuracy.

Ultrasound can be used in the evaluation of children with blunt head trauma to assess for skull fractures. (See Figure Below) The presence of a skull fracture increases the risk of traumatic intracranial hemorrhage 4- to 6-fold.

While the absence of a skull fracture does not rule out the presence of intracranial injury, assessment for skull fracture has been used to risk stratify.

Skull Fracture on Ultrasound

Patients with blunt head trauma. In a meta-analysis published in 2000, skull x-rays had a sensitivity of 38% and a specificity of 95% when interpreted by radiologists. Given this poor sensitivity, skull x-rays have been falling out of favor for assessment of skull fracture. However, there has been a renewed interest in skull ultrasound as perhaps a better tool to assess for skull fracture and to risk stratify patients with blunt head trauma.

Technique
Skull ultrasound is performed with a high-frequency linear array probe. The probe should be placed on the area of the skull with maximal tenderness, hematoma, or other sign of possible fracture. It should be scanned in 2 planes, looking for disruptions in the cortex. Sutures can be differentiated from fractures by following the cortical break to a fontanelle and by scanning the contralateral side for comparison. Additionally, the cortical break in a fracture will appear ragged, with sharp margins, while a suture will have a smooth appearance.

Several prospective studies have evaluated bedside ultrasound for skull fractures in children. Rabiner et al pooled data from previous trials along with their own data. They reported a sensitivity of 94% and specificity of 96% for ultrasound detection of skull fractures. Parri et al performed another study not captured in the Rabiner et al study, and showed a sensitivity of 100% and a specificity of 95%, with 1 false-positive result. A limitation of these studies was that the ultrasounds were performed on patients for whom a CT scan was planned. Therefore, the study population was already determined to be at higher risk for injury as compared to the entire spectrum of head trauma patients presenting to the ED. Nonetheless, it can be concluded that the diagnostic accuracy of skull ultrasound is superior to that of skull x-ray.

Future Applications
The current trend in the evaluation and risk stratification of pediatric head trauma is the incorporation of clinical decision rules, with the PECARN pediatric head injury prediction rule being the most sensitive and most commonly used in the United States.56 An area of future research is the incorporation of skull ultrasound in conjunction with a clinical decision rule to better risk stratify patients and possibly further decrease the number of CT scans being performed.

To read more about the PECARN Pediatric Head Injury Prediction Rule, go to: www.ebmedicine.net/PECARN-head-rule

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Last Modified: 09-19-2019
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