The objective of this study was to use a motion tracking magnetic resonance (MR) imaging technique in order to measure the in vivo quasi-static motion of the cervical spinal cord in human volunteers produced by varying degrees of flexion and extension. An initial preparation pulse consisting of a slice selective 180 degree pulse inverted the magnetization in a midsagittal section while the subject was in a neutral position. Before motion, tissue was tagged in multiple transverse planes using additional spatially selective radio frequency pulses. After the head-neck structure came to rest in its new position, a midsagittal MR image was obtained. This showed the movement of the tissue tag lines caused by the manoeuvre. A comparison of the tagged line pattern in MR images obtained with and without head movement revealed both the distortion of the cervical spinal cord and its displacement relative to surrounding structures. The results revealed the spinal cord moves and deforms considerably during the flexion and extension manoeuvre within the normal range of motion. These in vivo motion measurements form the foundation for more sophisticated studies to elucidate the biomechanical mechanisms responsible for traumatic spinal cord injury.
Abstract