CSF Flow Dynamics in Chiari I Malformation

We read with interest the article by Hofmann et al (1) in the January 2000 issue of the AJNR. In this study, authors used phase-contrast imaging in the axial plane to measure quantitatively the CSF and spinal cord motion at the C2 level in 18 patients with Chiari I malformation and in 18 healthy subjects. The authors concluded that in patients with Chiari I malformation, foramen magnum obstruction leads to increased systolic spinal cord motion and impaired diastolic spinal cord recoil and diastolic CSF motion. Although they found their results of spinal cord motion to be in keeping with one of our earlier studies (2), they concluded that their observations of CSF flow dynamics were different from our subsequent quantitative study (3) and the study of Armonda et al (4), both obtained with sagittal phase-contrast imaging.

In our 1995 publication (3), we used the analysis of CSF flow waveforms obtained by phase-contrast velocity measurements to compare the amplitude and temporal patterns of CSF flow in Chiari I patients and normal subjects at four different sites around the foramen magnum. It is apparent from the text and Figure 1 of the article by Hofmann et al (1) that their CSF flow measurements were not at our region 2 (immediately below the foramen magnum). It is at the region 2 that we found impaired systolic and unaltered diastolic CSF flow pulsations. It appears that Hofmann et al never measured CSF flow pulsations immediately below the level of foramen magnum and therefore may not be able to compare our results of region 2 with their own results. In fact, their results are similar to those we obtained at the region 3 (C2–C3 disk level) of our study. At region 3, we observed increased systolic and impaired diastolic flow pulsations that were more marked in patients with syringomyelia. Therefore, although the axial phase-contrast technique employed by Hofmann et al may be more sensitive for flow amplitude measurements than previous studies, their results are similar to previous studies obtained by sagittal imaging.