The pathogenesis of syringomyelia is incompletely understood. Since the condition is known to occur in association with hindbrain malformations and a variety of other lesions that occur at the level of the foramen magnum, attempts have been made to explain its development hydrodynamically. According to Gardner (Gardner et al. 1957; Gardner and Goodall 1950; Gardner and McMurry 1976), syringomyelia is caused by mechanical obstruction of the outlets of the fourth ventricle which results in a redirection of the cerebrospinal fluid (CSF) pulse wave into the central canal. The caudal focusing of the pulse wave presumably distends the central canal and leads to a net accumulation of fluid that may be confined to the lumen of the canal (hydromyelia) or may dissect into the paracentral tissues if the ependymal lining ruptures (syringohydromyelia).
