An accessory suture will usually not produce this appearance. When fractures extend into a major suture, there could be widening of the fracture line as it approaches the suture or there is associated diastasis of the adjacent synchodrosis or suture. In contrast, accessory sutures usually will show a zigzag pattern with interdigitations and sclerotic borders similar to major calvarial sutures (Fig. Simple non-depressed skull fractures are sharp lucencies with non-sclerotic edges. Radiographic differentiation of skull fracture and accessory suture CT scan with 3D reconstruction is vital in the further characterization of a questionable fracture. This pattern of development can therefore give rise to numerous accessory sutures that could be mistaken for fractures especially with plain film evaluation alone. On each side are the exoccipitals, ventrally located is the basoccipital and dorsally, the supraoccipital center contains the midline occipital fissure which can sometimes persist antenatally (Fig. The foramen magnum is surrounded by four ossification centers. The occipital bone has a more complex development. These are usually bilateral and fairly symmetrical but can at times be unilateral. They can be explained on the basis of incomplete union of the two separate ossification centers. An accessory intraparietal or subsagittal suture is rare but can be seen dividing the parietal bone (Fig. The parietal bone ossifies from two centers while the occipital bone ossifies from six centers. The parietal and occipital bones in particular are common regions for accessory sutures because of their multiple ossification centers. Therefore if cranial CT is deemed clinically necessary in trauma patients, questionable fractures can be confidently differentiated from unusual accessory sutures using these additional workstation capabilities. During the past decade, the increasing use of spiral and multidetector CT have lead to the ability of workstations to generate three-dimensional (3D) reconstructions of the skull.
Superimposition of normal suture lines like the metopic suture can mimic a fracture if one is not careful to obtain additional views. Minimal soft tissue swelling can be difficult to see even with oblique views. Plain film evaluation is especially challenging not only because of various artifacts that can degrade the study but also the inability to visualize intracranial processes, such as contusions and hemorrhage, that can substantiate a calvarial finding. However, in children this can be complicated due to the presence of numerous synchondroses and unusual accessory sutures. Plain film radiography remains the most cost effective method in evaluating skull fractures and can easily differentiate major sutures and common vascular grooves from fractures.
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