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Fig 3. Cardiac-related A/P motion data from a typical subject exhibiting motion of this type. Spinal cord displacement is indicated as a function of cardiac phase and R/C cord position (ie, vertebral level). Positive displacement values indicate anterior motion, whereas negative values indicate posterior motion. Clearly, cord displacements are maximal midway through the cardiac cycle and only at the level of upper-thoracic vertebrae. Conversely, motion dies off and is minimal (at any cardiac phase) at the level of mid- to lower-thoracic vertebrae. This pattern of decreasing motion along the cord, and quiescence in caudal regions, was also evident in other test subjects.
