Hi....I am not a dr, but have a related condition called chiari malformation...do u know if u have this as well?
Ur condition is a syrinx that developed in ur central canal....if it had been outside it would be called syringomyelia...many times they r too small for a shunt or stent to drain the excess CSF that fills the cyst like cavity.
But being in the central canal..it can be even more diff to drain....I am sure ur drs will want to see if another related condition is responsible for the development of this syrinx.
Be sure to see a specialist that deals solely with this condition or related conditions like chiari or syringomyelia...do not rush for surgery get several opinions.
We do have a forum here that deals with syringomyelia and chiari
http://www.medhelp.org/forums/Chiari-Malformation/show/257?camp=msc
Good luck
"selma"