How Well do We Evaluate Small Fiber Neuropathy?: A Survey of American Academy of Neurology Members

Clinical evaluation of distal symmetric polyneuropathy (DSP), which can include small fiber neuropathy (SFN), differs among neurologists, neuromuscular specialists, and internists. The American Academy of Neurology (AAN) 2009 Practice Parameter guides evaluation of DSP, but there are no guidelines or AAN practice parameters for the evaluation of SFN.

Determine how neurologists evaluate and test for SFN in their clinical practice and compare responses between neuromuscular (NM) and non-neuromuscular specialists (non-NM).

Eight hundred randomly selected AAN members, which included 400 members who indicated NM medicine to be a primary or secondary specialty, were selected to answer a survey about SFN. Respondents answered a survey instrument with a list of 44 serum tests and procedures for different neuropathy clinical scenarios.

The survey response rate was 29.3% (234/798), with 48.8% (N = 114) indicating that their primary specialty was neuromuscular. For an initial evaluation of distal symmetric SFN, respondents ordered a mean of 12 tests (SD 5.8) with a range of 0-26 tests. There was no statistically significant difference between the mean number of tests ordered by neuromuscular versus non-neuromuscular specialists. The 5 most common overall responses were complete blood count (87%), vitamin B12 (86%), basic metabolic panel (84%), thyroid stimulating hormone (78%), and hemoglobin A1c (77%). For a secondary evaluation of etiologies of distal symmetric SFN, 52% of non-neuromuscular specialists (95% CI, 42%-61%) versus 35% of neuromuscular specialists (95% CI, 26%-45%) would order a paraneoplastic panel. There was significant disparity in ordering a skin biopsy for intraepidermal nerve fiber density, with 65% of neuromuscular specialists (95% CI, 55%-74%) indicating that they would order this test compared with 38% of non-neuromuscular specialists (95% CI, 29%-48%).

The recommended studies with the highest yield for finding a cause of DSP were not universally ordered. There is variability in approaches to diagnosing SFN and searching for a possible etiology. The development of an AAN practice parameter for SFN may help promote consistent practice among neurologists of all subspecialties.