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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 25:142-145, January 2004
© 2004 American Society of Neuroradiology

SPINE

Effect of Craniocervical Decompression on Peak CSF Velocities in Symptomatic Patients with Chiari I Malformation

Maria T. Dolar^a,*, Victor M. Haughton^a, Bermans J. Iskandar^b and Mark Quigley^c

^a Department of Radiology, University of Wisconsin, Madison, WI
^b Department of Neurosurgery, University of Wisconsin, Madison, WI
^c Department of Medical Physics, University of Wisconsin, Madison, WI

Address correspondence to Victor M. Haughton, MD, Department of Radiology, University of Wisconsin Hospitals and Clinics, 600 Highland Avenue, CSC E3/311, Madison, WI 53792-3252

BACKGROUND AND PURPOSE: Peak CSF velocities detected in individual voxels in the subarachnoid space in patients with Chiari I malformations exceed those in similar locations in the subarachnoid space in healthy subjects. The purpose of this study was to test the hypothesis that the peak voxel velocities are decreased by craniocervical decompression.

METHODS: A consecutive series of patients with symptomatic Chiari I malformations was studied before and after craniocervical decompression with cardiac-gated, phase contrast MR imaging. Velocities were calculated for each voxel within the foramen magnum at 14 time points throughout the cardiac cycle. The greatest velocities measured in a voxel during the cephalad and caudad phases of CSF flow through the foramen magnum were tabulated for each patient before and after surgery. The differences in these velocities between the preoperative and postoperative studies were tested for statistical significance by using a single-tailed Student’s t test of paired samples.

RESULTS: Eight patients with a Chiari I malformation, including four with a syrinx, were studied. Peak caudad velocity diminished after craniocervical decompression in six of the eight patients, and the average diminished significantly from 3.4 cm/s preoperatively to 2.4 cm/s postoperatively (P = .01). Peak cephalad velocity diminished in six of the eight cases. The average diminished from 6.9 cm/s preoperatively to 3.9 cm/s postoperatively, a change that nearly reached the significance level of .05 (P = .055).

CONCLUSION: Craniocervical decompression in patients with Chiari I malformations decreases peak CSF velocities in the foramen magnum. The study supports the hypothesis that successful treatment of the Chiari I malformation is associated with improvement in CSF flow patterns.