Describing the typical appearance of skull fractures
In this video, from our Brain CT Essentials course, we'll teach you a powerful approach for finding subtle fractures on CT and the key clues you should watch for. You'll learn why the plane of the CT is important when searching for fractures, how the ear can help you locate a fracture, and how you should arrange the images for the best possible views.
A patient's history will often alert you to look for a skull fracture on a CT scan—but finding one isn't always as simple as it seems. In this video, from our Brain CT Essentials course, we'll teach you a powerful approach for finding subtle fractures on CT and the key clues you should watch for. You'll learn why the plane of the CT is important when searching for fractures, how the ear can help you locate a fracture, and how you should arrange the images for the best possible views.
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The patient's history will alert you when to look for skull fractures. And the best approach to finding fractures on CT images is to review the bone filtered images that are reconstructed thinner than five millimeters. These should be reviewed in at least two reconstruction planes for example axial and coronal.
While some fractures are quite evident, as they are in these two patients with depressed skull fractures, they are more often quite subtle. When you see a depressed skull fracture, look carefully at the underlying brain since there can be an associated contusion or subarachnoid hemorrhage, as you can see in the right image in a patient who was struck with a hammer.
And you should direct your search on the images where there is evidence of soft tissue swelling overlying the skull. In this case, this soft tissue swelling will lead your eye to the fracture. Then direct your gaze to the other side of the brain, since contusions and subdural hematomas, are almost always on the opposite side from the impact.
When the fracture line runs in the same plane as the reconstruction, it can be very difficult for the imager to perceive the fracture. For example, this fracture is at the limit of perception on axial views in this trauma patient, but it is quite evident on the sagittal reconstruction of the same data. Fractures can be differentiated from sutures in most cases, generally by there straight course and sharp margins.
For example, the blue arrows point to the sutures in this child but the yellow arrow indicates a skull fracture. In the setting of trauma, whenever you see fluid in the middle ear on CT, you should search for an associated skull base fracture on the same side. While the fracture in this case is faintly visible on the axial scan, it's much more evident on the thin reconstructions seen in the coronal plane.
As with all suspected fractures, it will be more evident if you arrange to have the images reconstructed in these thin sections. If you're looking at five millimeter thick sections and volume averaging can obscure these fine nondisplaced fractures. When reviewing CT images you should also look for air, where there should be soft tissue, or fat or soft tissue where there should be air.
This patient has a fracture of the medial orbital wall that can be seen after a bloated eye, frequently from a fist or a squash ball, and this is called a medial blowout fracture. As a result of this fracture involving paranasal sinus, some air from the sinus enter the patient's orbit. The presence of intracranial air, even a small amount is abnormal and in the setting of trauma should direct you to carefully search for a fracture involving the paranasal sinus or mastoid air cells.
In this case, there was a skull base fracture through the mastoid that was visible on thin reconstructions. Another common facial fracture is the inferior orbital blowout fracture from a similar mechanism of trauma. These fractures are difficult to recognize on the axial imaging alone and I find are always easier to see on coronal imaging.
Note the displacement of fat from the orbit into the maxillary sinus in this case, and you can predict that this particular fracture is chronic because there's no fluid or blood products in the maxillary sinus. This patient had an acute left sided orbital blowout fracture. Note the displaced fragment from the inferior orbit and that the fracture is easier to recognize on coronal reconstruction.
The soft tissue or blood around the displaced fragment of the orbital floor is typical with an acute fracture. You see evidence of a fracture on this image on your right? It's hard to see. The coronal reconstruction on your left reveals that this patient has a fracture of the right mandible. That resulted in dislocation of the same side mandibular condyle that is displaced out of the condylar fossa at the skull base.
That finding is frequently missed on the axial image. An unusual location of the mandibular condyle is this sign of a possible mandibular fracture, so look for this sign on CT scans in trauma patients. A fracture of the medial occipital condyle is another fracture that's commonly missed but important to look for since it implies an injury to the stabilizing ligaments, in this case the alar ligament that can lead to late instability.
Your chances of identifying a skull fracture will be improved by optimizing the way you review the CT scan images in trauma patients. Take the time to review bone filtered images and rather than use coronal imaging only when you have a question on the axial imaging, review them with the same attention you devoted to the axial views. That's because many traumatic scull and facial fractures can only be perceived when viewed in the coronal plane.