I Am Scheduled To Have A Cyst Removed From L-4.

i am scheduled to have a cyst removed from L-4. My dr says my pain is not typical of the nerve pain associated with lumbar stenosis. my problem is severe sciatica, starting in buttocks and travels to lateral side of leg to knee. I am concerned i may have injured piriformis muscle. none of my doctors will even address this. i do not have back pain, but sciatica has nearly stopped me from walking or being on myh feet. how can i determine if this is piriformis muscle?