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Chiari I malformations: assessment with phase-contrast velocity MR
S M Wolpert1, R A Bhadelia, A R Bogdan
1Department of Radiology, New England Medical Center Hospitals, Boston 02111.
AJNR. American Journal of Neuroradiology
|August 1, 1994
Summary
Patients with Chiari I malformations exhibit abnormal tonsillar movement and posterior medulla displacement. Cerebrospinal fluid flow is normal except for absent vallecular flow, suggesting potential surgical targets.
Area of Science:
- Neurology
- Neurosurgery
- Medical Imaging
Background:
- Chiari I malformation involves cerebellar tonsil herniation through the foramen magnum.
- Understanding cerebrospinal fluid (CSF) dynamics is crucial for Chiari I malformation assessment.
Purpose of the Study:
- To evaluate the movement of the medulla, cerebellar tonsils, and upper cervical cord.
- To assess posterior fossa CSF pathways in normal subjects and those with Chiari I malformation.
Main Methods:
- Phase-contrast cine MRI was used to examine 9 healthy volunteers and 8 patients with Chiari I malformations.
- Region-of-interest cursors and intensity-versus-time graphs quantified brain and CSF movement.
Main Results:
- Chiari I patients showed normal CSF flow patterns, except for absent vallecular flow.
- Tonsillar velocities were 10 times higher in Chiari I patients.
- Medulla exhibited posterior movement in Chiari I patients, contrasting with anterior movement in controls.
Conclusions:
- Elevated tonsillar velocities may result from direct impact of the carotid systolic pulse within the foramen magnum.
- The Bernoulli effect in the confined space could also contribute to increased tonsillar velocities.
- Surgical intervention may lead to a reduction in peak tonsillar velocities.