Radicular in this case is referring to radiating pain down his legs. When there is exiting spinal nerve root compression (or stenosis), then you can have pain that extends to whereever that nerve root supplies. If you take a look at a dermatome map, then you can see whether the corresponding nerve root is a possible causative for extremity pain.

One thing to note is that each radiologist reads an MRI and reports, often using similar langage for the same things...and other times, they miss things completely, and sometimes the body changes enough, that what was seen at one point is no longer as markedly present in the future. Another difference could be between the position of the MRIs...one was standing and the older was a supine MRI (laying down)? His stenosis could be related to load bearing.

Just based on what you've written, my best guess that the L4-L5 nerve roots are the cuplrit for his neuropathy, barring any other causes. Of course, I'm not a doc, so I could be full of hooey.

Best of luck to you.

Theresa