Mine SFN is non-length dependent. I had an unusual biopsy which showed increased fibres. My neuro thinks inflammatory and put me on a week of intravenous methylprednisolone. I didn't find it helped much. He has secured a trial of IVIG on NHS. I haven't tried it yet as symptoms have subsided quite a bit. My neuro seems to think that NLD SFN is an inflammatory neuropathy.