Linear fractures occult on skull radiographs: a pitfall at radiological screening for mild head injury.

Background: Skull radiography is widely used to screen for fractures in patients with mild head injury. However, the clear depiction of a fracture requires a gap in the skull separated by the fracture that is wide enough to allow the passage of x-rays. We studied atypical linear fractures that were not visualized clearly, because a specific anatomical configuration hampered the passage of x-rays.

Methods: We retrospectively evaluated 278 patients with mild head injuries who had undergone routine skull radiography (anteroposterior and lateral views) and head computed tomography (CT). We found that some patients negative for linear fracture on skull radiographs were positive on bone window CT scans.

Results: Of the 278 patients aged between 2 months and 66 years, 8 (2.9%) manifested a linear fracture on CT scans that presented as a cross section of the fracture oblique to the direction of the x-rays. Four of the 8 developed acute epidural hematoma; 2 of these patients underwent craniotomy.

Conclusions: Radiographic study returned false-negative results, because x-rays were absorbed by the double-layered skull along fractures whose cross section was oblique to the direction of the x-rays. The evaluation of head injury by radiography only may miss these fractures and their undetected presence may result in sequelae such as intracranial hematoma.