A pitfall in neck pain: occult odontoid fracture.

Type III odontoid fractures of the axis are the second most common injuries of the cervical spine. Most of these result from motor vehicle accidents and falls. Occult odontoid fractures without preceding trauma are rarely reported in the literature and may be difficult to diagnose. We report the case of a healthy patient who had no history of trauma, but sustained sudden pain in the neck and guarding during head movement after sleep. Initial radiographs of the cervical spine including open-mouth, anterior-posterior, and lateral views did not reveal any obvious fractures. Type III odontoid fracture was uneventfully diagnosed via high-quality three-dimensional reconstruction of computed tomography. The possible mechanism was hyperextension of the neck during the change from the supine to the sitting position. Type III odontoid fractures can occur in the absence of major trauma. The usefulness of computed tomography is emphasized and the literature is also reviewed.