The Value of Including Sweat Gland Nerve Fiber Density (SGNFD) Analysis in the Neuropathy Work-up (P6.088)

Objective: Assessing the clinical value of adding Sweat Gland Nerve Fiber Density (SGNFD) analysis to Epidermal Nerve Fiber Density (ENFD) when working up patients with neuropathic complaints. Background: Patients with sensory neuropathy have autonomic complaints which are hard to document. It is even harder to diagnose autoimmune autonomic neuropathy (AAN). In the past few years it became possible to quantify SGNFD in the same skin sample used to determine ENFD. (Christopher et al. Neurology , 2009; 72: 1479 - 1486). These fibers originate from the sympathetic ganglia, whereas the regular sensory fibers originate from the dorsal root ganglia. Damage to one group of fibers and not the other may implicate ganglionic damage of immune origin. Methods: From October 2010, to October 2013, we performed 94 biopsies (analyzed at Therapath, LLC) studying both ENFD and SGNFD in 76 patients (32 females; age 19 - 66; mean 52.3). Sixteen patients had multiple biopsies in this period of time. Results: 66/94 (70.2%) of all biopsies showed low ENFD, SGFD, or both. Thirty showed both. 29/66 (44%) showed low SGNFD and normal ENFD. Seven (10.6%) showed normal SGFD and low ENFD. 36/94 (38.3%) of all biopsies showed discrepancies, in the same 3mm skin sample. Conclusion: Adding SGNFD to ENFD increased the yield of abnormal biopsies (test sensitivity) by 78.4% (from 37 to 66). The percentage of abnormals rose from 39.3% (37/94), to 70.2% (66/94). SGNFD should be routinely added to ENFD for diagnosing small fiber neuropathy. It is a reliable histopathological measure that can detect autonomic neuropathy prior to clinical symptomatology, or at the absence o other supporting evidence. A discrepancy between ENFD and SGFD is an indirect proof of autonomic (ganglionic) neuropathy, even in the lack of anti ganglional AChR (nicotinic) antibodies Disclosure: Dr. Katz has received personal compensation for activities with Forest Laboratories, Inc. as a speaker. Dr. Berkley has nothing to disclose.