Small Fiber Neuropathy-caused by Lumbar nerve damage?

[nodsirrah]

I have Idiopathic Small Fiber Neuropathy confirmed May 2012 by skin biopsy.
I had a Foraminotomy in 2007 because of Sciatica pain in my right leg, shortly thereafter I had numbness and needle pricks in my right thigh, the Neurological surgeon said it would go away in the near future, yeah right!
In March, this year, after severe Sciatica nerve pain I had L3, L4, L5 fused by a Orthopedic Surgeon. Shortly thereafter I had numbness and needle pricks in both legs and burning feet.
The Neurologist I am now seeing said he doubted the SFN could be caused by damage to the Lumbar nerve. He told me to buy Metanx and come back in 2 months, the Metanx has done nothing, nor did Gabapentin.
Since he has not found the cause of the SFN I can only guess it is most likely nerve damage or nerve compression in the Lumbar region.
Are there any tests that I can politely suggest to him that will confirm or reject my opinion?

[glenntaj]

--to have an isolated small-fiber syndrome just from lumbar compression/radiculopathy; in such cases one usually has evidence of larger, myelinated nerves having been damaged as well. Have you had a full lower extremity nerve conduction/EMG series done, including the paraspinal muscles of the lower back, to try and see if there is signal disruption there?

None of us are excused from being "co-morbid"--one can have lumbar or sacral compression and have other things going on as well. In fact, there is something called the "double crush hypothesis", which theorizes that nerves already damaged by some process can get mechanically compressed and produce symptoms greater than one would suspect from "the sum of the parts".

As far as testing, have you seen the LizaJane spreadsheets at lizajane.org? These were designed to be about as comprehensive a series of possible tests for neurological symptoms as some very wide-ranging minds could come up with; you might want to take a look and see what you've already had, and not had.