Many hypotheses concerning pathogenesis of syringomyelia were abandoned because 
of evidence found in more recent investigations. We should rank among them the 
"classical" theories of Gardner and Williams based on the assumption that 
syringomyelic cavities result from directing the fluid from the fourth ventricle 
to the central canal of the spine in the case of disturbances of circulation of 
the cerebrospinal fluid in the region of the cranio-spinal junction. The theory 
of intraspinal pulsation pressure of Greitz may explain the pathogenesis of 
syringomyelia in the case of obstacles to fluid flow from the cranial cavity to 
the spinal canal as in patients with Arnold-Chiari syndrome. The origin of 
Arnold-Chiari syndrome is connected with narrowness in the posterior fossa, 
particularly with narrowing of the arachnoid spaces. Improvement of clinical 
condition after surgical restoration of the fluid spaces within the posterior 
cranial cavity and improvement of cerebrospinal fluid flow in the region of the 
cranio-cervical junction are factors supporting this opinion.