The goal of this study is to establish the mechanism(s) of progression of communicating syringomyelia. This type of syringomyelia usually accompanies problems around the base of the skull. Our hypothesis is that cerebrospinal fluid flow is altered in such cases. Cerebrospinal fluid is directed into the spinal cord rather than through normal pathways and a syrinx results. Treatment depends on re-establishing normal cerebrospinal fluid flow patterns at the craniocervical junction. Preoperative and intraoperative radiographic and physiologic measurements will provide data which will test our hypothesis. The operation that we will perform will improve the flow of the spinal fluid through normal pathways and not into or through the syrinx. The best treatment for syringomyelia has not been established. Present surgical treatment results in disease stabilization in many, but not all patients, although objective improvement is less common [1]. Delayed deterioration is not uncommon. Measurement of the physiological parameters of intraventricular pressure, intrathecal pressure, and intrasyrinx pressure should provide data which elucidate the hydrodynamic mechanism(s) of progression of syringomyelia. Radiographic evaluation, including cerebrospinal MRI, ultrasonography, and Imatron CT will be used to evaluate the pathologic anatomy, including possible connections of the syrinx with the fourth ventricle. Correlation of the anatomic and physiologic measurements should provide data which indicate the mode of progression of syringomyelia and which may have implications for the optimal treatment of syringomyelia.