Syringomyelia is a cavitation of the spinal cord. It most commonly occurs in association with structural abnormalities of the foramen magnum. We plan to assist SNB in the acquisition of pressures in the ventricle, syrinx, and spinal subarachnoid space. The data will be evaluated in connection with anatomic information obtained by cerebrospinal MRI, ultrasonography, and Imatron CT. Correlation of the anatomic and physiologic measurements should help to elucidate the mode of progression of syringomyelia, and may have implications for its treatment.