Syringomyelia is a poorly understood disease process, and widespread use of MR imaging has shown that it is more prevalent than previously suspected. The pathogenesis of syringomyelia in Chiari I patients remains an enigma, and although treatment methods are available, their effectiveness is not clearly understood. MR provides the only non-invasive, quantitative, spatially accurate method to study in vivo CSF dynamics in normal subjects and in syringomyelia. In this research project, we will use the most up- to-date quantitative MR methods to measure CSF flow and brain motion in Chiari I patients with syrinx, Chiari I patients without syrinx, and normal subjects. We will test the hypothesis that the pathogenesis of Chiari I syrinx is related to obstruction of CSF flow at the foramen magnum which leads to decreased intracranial capacitance, increased CSF and brain displacement, and eventual fluid pulsation in the syrinx when it becomes large enough to obstruct CSF flow in the spinal SAS. We will: (1) compare phase-contrast cine MR and cine spin-tagging sequences to each other and validate the measurements with physical measurements in a computer controlled pulsatile motion phantom; (2) obtain normative data for aqueductal oscillatory flow (ml/cardiac cycle), net aqueductal flow (ml/min of CSF production), brain and CSF volume displacement through the tentorial incisura (ml/cycle), pulsatile brainstem displacement (ml/cycle), and CSF flow above and below the foramen magnum (ml/cardiac cycle); (3) determine the distribution of volume expansion in the normal spinal canal; and (4) measure arterial in-flow and venous out-flow throughout the cardiac cycle to calculate arterio-venous difference (which is an indirect measure of intracranial capacitance). These measurements will not only characterize CSF flow in the normal person, but will be important parameters for comparison to the abnormal CSF flow seen in Chiari I syrinx patients. In syrinx patients, we will obtain additional CSF flow measurements at several levels of the syrinx and adjacent subarachnoid space (SAS). The quantitative techniques will provide an explanation of the beneficial effects of suboccipital craniectomy and yield quantitative MR criteria for evaluating the success of treatment and/or recurrence. The quantitative data may further provide a risk assessment for Chiari I patients who have not yet developed syrinx. Basic to these physiological and clinical studies are the technical MR tools for quantitative measurement. Existing MR pulse sequences and analysis prograins will be further refined for improved performance in the clinical environment. The quantitative techniques for studying CSF dynamics and the CSF data from this investigation will have wide application for studying CSF pathophysiology beyond that seen in syringomyelia, including hydrocephalus and other disorders for which CSF shunting is indicated.
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