Is hydrocephalls causes syringomeliea?

No, not quite. Obstruction of the cerebrospinal fluid flow can result in syringomyelia formation. A number of disorders can cause an obstruction of the normal cerebrospinal fluid flow, such as chiari malformation, spinal arachnoiditis, scoliosis, spinal vertebrae misalignment, spinal tumors, spina bifida, etc... It's possible for such disorders to cause both the hydrocephalus and the syringomelia.