These are some noted from Dr Ravi Ramakantan’s talk on cervical spine and craniovertebral junction radiography.
1. Many of these x-rays (as also CTs) are taken in an emergency situation with the patient having suffered trauma. It is the responsibility of the radiologist to ensure that the patient is correctly shifted from the stretcher for the X-ray/ CT with a cervical collar in place to ensure that there is no harm to the patient during the study.
2. There is an important difference in the technique of taking a lateral skull film compared to a lateral cervical spine/CVJ film. In the former, the patient may lie supine and turn his/her head laterally and the film may be taken. However, the latter needs to be a true lateral of the spine. Hence, it is taken either in sitting/standing position in the routine setting with patient being erect and lateral to the cassette, or with the patient lying supine in an emergent situation with a cross table lateral performed.
3. A simple way to confirm that there is no significant angulation on the lateral film is to see that the angles of the mandible reasonably overlap. Mastoid overlap may also be checked.
4. In cases of acute trauma, first see the precervical soft tissue. An increase in the precervical soft tissue thickness indicates underlying fracture/dislocation. According to Dr Ravi Ramakantan, pure eyeballing should be a good way to rule out precervical soft tissue swelling in most cases (if an experienced radiologist needs to actually measure the thickness with a scale, it is usually going to be equivocal or borderline swelling). However, for exam purposes, the thickness of the soft tissue should be around 4 mm at C2-C4 level. As we go inferiorly, it becomes thicker due to the presence of the esophagus. The thickness should then not exceed approximately 3/4th of the sagittal diameter of the adjacent cervical vertebra.
5. In elective x-rays (particularly suspected spondylosis), have a look at the spinal canal diameter (sagittal diameter between posterior spinal line and spinolaminar line). It should not be less than 20 mm at the C1 and C2 levels, and 13 mm further inferiorly; else it indicates the presence of spinal canal stenosis.
6. Presence of atlantoaxial instability in an elective setting (say in a patient with Down’s syndrome) is best assessed with a flexion view study. Given that the transverse ligament is lax, the instability leads to increased subluxation on the flexion view (imagine the patient flexing his/her neck; the anterior arch of atlas will go away from the odontoid in the absence of the ligament to hold the two in place). Extension may not unmask this instability. Hence, it is best to evaluate atlantoaxial instability on flexion views.
7. If a radiologist detects atlantoaxial instability, it is his/her duty to immediately call up the referring doctor and inform, as the patient may need a cervical collar in place to prevent unexpected damage. Also inform the patient regarding the same. Document the communication in the report. Dr Ravi Ramakantan talked of a true incidence in KEM when this did not happen, and the radiologist instead simply wrote the report for the referring doctor to see on a routine basis. Unfortunately, the child rolled off his bed in the interim time and developed quadriplegia due to atlantoaxial dislocation.