Si & sciatica pain, possible saddle numbness & what goes w/it. mri lower back shows nothing. cervical mri shows c5-6, c6-7 mod-severe bulging disc oseophyte complex, mild stenosis, mild neural foraminal narrowing +. could any of this be related?

The change in your cervical spines is not the cause of your presumed SI & sciatica pain. Because the lumbosacral spines are relatively normal, you may suffer from pyriformis syndrome rather than SI and sciatica. You should be examined by an experienced orthopedist or rheumatologist. Good luck.

The neck issues have no relationship to the lower back symptoms. An EMG study may help further understanding of your sciatica, which could be due to peripheral mechanisms. See a physiatrist and obtain a thorough evaluation.