Clinical History
A 73-year-old female patient was admitted to the emergency department with a history of fall and subsequent trauma of the head. The patient complained of mild dizziness, headache and pain in the neck. The rest of the clinical examination was unremarkable.
Imaging Findings
The time interval between brain trauma and admission to the hospital was half an hour, whereas the CT examination was performed two hours after the admission. The patient initially underwent frontal and lateral cervical spine radiography which revealed a radiolucent line in the base of the odontoid process. There was also suspicion of posterior displacement of the dens because its posterior surface was not aligned with the posterior surface of the body of C2 and the rest of the vertebrae. Thus, there seemed to be discontinuity of the anterior and posterior cervical lines. (Fig. 1)
The patient then underwent multidetector CT of the cervical spine which confirmed the existence of a radiolucent line in the base of the odontoid process. There was also a 5 mm posterior and mild right-lateral displacement of the dens. The spinal canal was not compromised. (Fig. 2, 3, 4, 5)
Discussion
Injury of the cervical spine is usually caused by vehicle accidents, diving into shallow water and athletic activities and affects patients under 24 years and older than 55 years of age. [1]
Dens fractures (DF) constitute the commonest type of fracture of the cervical spine, representing 5-15% of all cervical spine fractures and are divided in three types. Type I refers to a fracture involving the superior part of the odontoid process while Type II involves its base and Type III affects the body of C2. [2]
Due to aging, the pain may be minimal in old patients where the neurologic deficit must be taken into account. [2] The Canadian C-spine rule can be used when examining patients suspected of cervical spine fracture to decide whether imaging is needed or not. [3]
The fracture line and the displacement of the distal fragment are the two direct signs of DF in radiography. [1] When evaluating a lateral radiography, the distance between the anterior surface of the dens and the anterior arch of atlas must not exceed 3mm in adults and 5mm in children and the posterior surface of the dens must form a continuous line with the posterior surface of the body of the C2. Swelling of the prevertebral soft-tissue (with thickness greater than 7mm) and disruption of the ring of C2 (Harris’s ring) are indirect signs of fracture on the lateral radiograph, with the latter raising suspicion of a type III fracture. [4, 5]
CT can be used as primary imaging modality in multiorgan trauma patients or when plain radiographies are inadequate. MPR images may reveal fractures not visible on axial images due to their plane. CT has been shown to be 98% sensitive in detecting spine injury in high-risk patients whereas radiography was 52% sensitive. Consequently, multidetector CT of the cervical spine is usually included in the total body screening of patients with severe trauma. However, in low-risk patients with suspected cervical injury, there is not enough evidence that CT should replace radiography. [3]
MRI can better demonstrate soft-tissue (ligaments and cartilage) and spinal cord injuries. [4]
Type I fractures can be treated with cervical arthrodesis for three months. [1] Type II and III fractures are considered unstable and are frequently complicated by nonunion due to the poor vascularity of the area. Thus, these fractures are treated with external immobilization with a halo vest or surgery. [2]
Differential Diagnosis List
Fracture of the odontoid process (type II)
Fracture of the odontoid process
Os odontoideum
Persistent ossiculum terminale
Mach effect
Final Diagnosis
Fracture of the odontoid process (type II)
