Radiologic spectrum of craniocervical distraction injuries.

Injuries to the atlanto-occipital region, which range from complete atlanto-occipital or atlantoaxial dislocation to nondisplaced occipital condyle avulsion fractures, are usually of critical clinical importance. At initial cross-table lateral radiography, measurement of the basion-dens and basion-posterior axial line intervals and comparison with normal measurements may help detect injury. Computed tomography (CT) with sagittal and coronal reformatted images permits optimal detection and evaluation of fracture and luxation. CT findings that may suggest atlanto-occipital injury include joint incongruity, focal hematomas, vertebral artery injury, capsular swelling, and, rarely, fractures through cranial nerve canals. Magnetic resonance (MR) imaging of the cervical spine with fat-suppressed gradient-echo T2-weighted or short-inversion-time inversion recovery sequences can demonstrate increased signal intensity in the atlantoaxial and atlanto-occipital joints, craniocervical ligaments, prevertebral soft tissues, and spinal cord. Axial gradient-echo MR images may be particularly useful in assessing the integrity of the transverse atlantal ligament. All imaging studies should be conducted with special attention to bone integrity and the possibility of soft-tissue injury. Atlanto-occipital injuries are now recognized as potentially survivable, although commonly with substantial morbidity. Swift diagnosis by the trauma radiologist is crucial for ensuring prompt, effective treatment and preventing delayed neurologic deficits in patients who survive such injuries.