I've been dxed with SFN but only have symptoms induced by my inhaler medications so am not sure quite how to characterize it. I get arm weakness too but only when I have taken enough med to have SFN symptoms so for me at least I would say the weakness is neuropathy.

I also have had an MRI that showed cervical radiculopathy, I get neck pain which is also exacerbated/intensified by meds (the gift that keeps on giving ) but the only other symptom I have known for sure to be from the radiculopathy is that when I first noticed something was amiss occasionally it felt like something slipped out of place and I could not raise my arms. There was no sensation of weakness, arms just didn't work.

You comment about an inflammatory source was interesting to me, I have wondered that for myself as well.