Skull Fracture

Diagnosis Definition

• Skull fractures can be linear/non-displaced (most common), sutural diastasis (affecting newborns and infants), depressed (inward or outward), comminuted (multiple fragments), burst (variant of comminuted, typically associated with vertebral trauma), or open/compound (communicates with air)
• Fractures involving paranasal sinuses or temporal bone air cells are potential sites of intracranial communication and a route of infection, cerebrospinal fluid leak (rhinorrhea, otorrhea), or pneumocephalus
• Skull fractures in infants can represent nonaccidental trauma, classically seen in an infant about 6 months old with retinal hemorrhages, subdural hematoma, and absent/minimal signs of external trauma

Imaging Findings

• CT better defines bone fractures than MRI and can also screen for intracranial traumatic injury (e.g., hemorrhage, herniation, hydrocephalus)
• CT window level/width should be adjusted to assess for different types of injury: 1) wide soft tissue window for scalp injury/site of impact, pneumocephalus, and extra-axial hematoma, 2) bone algorithm/window for skull fracture, and 3) brain window to evaluate for brain contusion/shearing injuries, ventricular/cisternal blood, and cistern effacement and herniation
• MRI can be used to evaluate associated non-bony injury and is particularly useful in cases of new or deteriorating cognitive or neurologic deficits, delayed recovery, or persistent unexplained deficits; it is more sensitive than CT for skull base hematomas and shearing injuries

KEY IMAGES

Pearls

• Presence of a scalp injury should prompt a search for an associated skull fracture
• Fractures with fragment depression greater than the adjacent inner table may require surgical elevation
• Vascular grooves/channels are differentiated from fractures by having a branching pattern, appearing wavy rather than sharp and straight, tapering, and showing symmetry with the opposite side
• In the setting of trauma and opacified mastoid air cells, a temporal bone fracture should be assumed until proven otherwise

References

1. Shetty VS, Reis MN, Aulino JM, Berger KL, Broder J, et al.  ACR Appropriateness Criteria Head Trauma.  J Am Coll Radiol 2016; 13(6):668-679
2. Zayas JO, Feliciano YZ, Hadley CR, Gomez AA, Vidal JA.  Temporal Bone Trauma and the Role of Multidetector CT in the Emergency Department.  RadioGraphics 2011; 31:1741–1755