Phase-contrast magnetic resonance imaging study on cord motion in patients with spinal dysraphism: comparison with healthy subjects.

Cord motion at the cervical cord (C-3) level was measured with phase-contrast magnetic resonance imaging (MRI) in 39 healthy young subjects and 34 age-matched patients with spinal dysraphism. Cord velocity curves (composed of waves I, II, and III) were made in both sagittal images and transverse images and classified into 3 types. The measurement in the sagittal images were more reproducible than that in the transverse images. In healthy subjects, the mean cord velocity of wave I was 0.49 +/- 0.11 cm/s in the sagittal image. In the subgroup of patients with spinal dysraphism showing stable clinical courses, cord velocity was comparable to that in the healthy subjects. Patients of the subgroup with symptomatic aggravation showed a significant decrease in cord velocity in wave I, and a characteristic pattern in the cord velocity curve: the velocity change (wave I) was small. This decrease in cord velocity was thought to be due mainly to cord tethering. The measurement of cord motion with phase-contrast MRI could give objective and quantitative information about cord motion and tethering associated with spinal dysraphism.