You are mixing spinal stenosis and epidural scar presence. It is exceedingly rare for scar to fill the entire canal so epidural scar is uncommon to cause central stenosis. Now, if there was previous surgery and an unappreciated preexisting narrowing of a section of the canal (lateral recess or foraminal stenosis), scar can make the nerve symptoms worse and redo surgery can be effective.
Dr. Corenman