CSF flow through the upper cervical spinal canal in Chiari I malformation.

BACKGROUND AND PURPOSE Previous studies have quantified CSF flow in patients with Chiari I at the foramen magnum with single-axial or single-sagittal PCMR. The goal of this study was to measure CSF velocities at multiple cervical spinal levels in patients with Chiari I malformation. MATERIALS AND METHODS In a patient registry, consecutive patients without surgery who had PCMR flow images in 5-8 axial planes between the foramen magnum and C4 were identified. Four contiguous regions were defined from the foramen magnum to C4. In each region, the fastest positive flow (PSV) and fastest negative flow (PDV) were tabulated. Changes in peak velocity by cervical spinal level and age and sex were tested for significance with linear mixed-effects models. RESULTS In 17 patients studied, PSV increased progressively and significantly from the foramen magnum to C4. PDVs increased slightly from the foramen magnum to C3. The changes in velocity over the 4 regions tended to be smaller in the 13 patients with tonsilar ectopia than in the 4 patients without it. Age and sex had an effect on peak velocities. CONCLUSIONS Peak diastolic and systolic CSF velocities are significantly greater below than at the foramen magnum.