Three midline magnetic resonance images (MRI) of the cervical spine in neutral, flexion and extension. 

With neck movement, the protective channel of the spinal canal can change shape in some patients.  And unknown to patients and clinicians, because the classic cervical MRI does not include flexion or extension images, the spinal cord can be compressed (arrows) leading to significant neuropathic pain.  First reported in 1998, by C Muhle and D Resnick as reviewed in the Practical Pain Management review (Dec. 2012)

This web site provides information for individuals interested in PC3.