Is it uncommon to have an arachnoid cyst in the spinal canal in c-spine region? It's behind the spinal cord pushing it up, have congenitally small canal

It's. NOT COMMON but is seen in the entire slinal canal from the neck to lower back. It can be drained by an INTERVENTIONAL Radiologist and may or may not resolve permanently. A neurosurgical consultation is probably your next step.... Hope this helps! Dr Z.