I am a radiologist, so most of my clinical (i.e. not anatomic) knowledge of PN is based off of what I learned in medical school plus additional reading based on my own battle with PN. If your symptoms are just in a foot or feet, it could be because of you disk disease. Your MRI info on your disk disease is not specific enough. They should be able to tell you if it narrows your central spinal canal, lateral recesses, or neuroforamen. If so, they should grade the severity of the narrowing and whether or not the disk is directly impinging a nerve root or not.

I typically do LPs at L2-L3 or L3-L4, so your degenerative changes based on your MRI should not make the LP any more complicated.

Hope this helps.