Atlanto-occipital dislocation with upper cervical spinal cord injury difficult to detect on postmortem computed tomography: a case report.

Atlanto-occipital dislocation (AOD) is a high-energy traumatic injury associated with poor prognosis. Here, we report a case of AOD that could not be detected on postmortem computed tomography (PMCT). A man in his 70s was driving on a public road when he collided with a guardrail and struck an oncoming vehicle. At the time of contact with the emergency team, he was already in cardiopulmonary arrest. PMCT revealed hemorrhage in the third and fourth ventricles and around the brainstem suggestive of the pseudo-CT myelogram sign, as well as marked cervical deformity and fusion suggestive of diffuse idiopathic skeletal hyperostosis (DISH); however, no definite cervical spine injury could be identified. At autopsy, no significant external injuries were found; however, hemorrhage within the posterior cervical musculature and subarachnoid hemorrhage over the cerebellum were present. Observation of the spinal canal demonstrated hemorrhage at the atlanto-occipital junction, and a corresponding hemorrhage was also noted on the transverse section of the cervical spinal cord. The cause of death was judged to be cervical spinal cord injury associated with AOD. In this case, the dislocation of the neck was presumed to have been caused by excessive flexion resulting from the impact from the vehicle collision, with DISH being a contributing factor. Even in the absence of external injuries or CT-detectable cervical spine abnormalities, when abnormal cervical motion is suspected in fatal cases-particularly when postmortem CT shows DISH or a pseudo-CT myelogram sign-AOD or related cervical spinal cord injury should be considered.