Disclosures: Francis P. Lagattuta, MD: No financial relationships or conflicts of interest

Objective: For patients with small fiber neuropathy (SFN), corneal confocal microscopy (CCM), epidermal nerve fiber density (ENFD) testing, Q-sweat tests and autonomic nerve system (ANS) testing all identify nerve fiber deficits. We compared CCM results to the other tests.

Design: A retrospective study. Pain patients positive for the screening test underwent all four tests. CCM and ENFD tests were conducted on 138 patients; 51 patients had the Q-sweat test; and 67 patients underwent ANS testing. Setting : Outpatient pain clinic Participants : Patients at an outpatient pain clinic

Interventions: Not applicable

Main Outcome Measures: What diagnostic test can diagnose SFN

Results: One-quarter of the patients had positive results for both CCM and ENFD. One-third had a positive CCM and a negative ENFD. Thirty-five percent had negative CCM and positive ENFD. Forty percent were negative for both for both CCM and ENFD. Thirty-four percent had a negative CCM and a positive Q-sweat. Forty-eight had a negative CCM and a positive ANS. Eighteen percent of patients had a negative ENFD and a positive Q-sweat, and 24 percent had a negative ENFD and a positive ANS. Four patients were negative for all four tests. Conclusions: In one-third of the cases, despite a negative CCM, the ENFD was positive. The CCM also was negative in 34 percent of positive Q-sweat tests, and 48 percent of ANS tests. The Q-sweat, ANS and CCM were positive 18 percent, 24 percent and 33 percent, respectively, with a normal ENFD, showing there can be SNF even with a normal ENFD. Therefore, all four tests need to be done.

Level of Evidence: Level IV

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/ccm-enfd-and-ans-results-in-patients-with-sfn/