Sural sensory nerve action potential, epidermal nerve fiber density, and quantitative sudomotor axon reflex in the healthy elderly.

INTRODUCTION

Polyneuropathy evaluation in older patients is often challenging due to conflicting data regarding normative values for peripheral nerve testing.

METHODS

We characterized the results of sural nerve conduction studies, intraepidermal nerve fiber density (IENFD), and quantitative sudomotor axon reflex testing (QSART) in a prospective study of 50 healthy subjects aged ≥60 years.

RESULTS

Of the 50 subjects, 48 (96%) had an obtainable sural sensory nerve action potential (SNAP). Using quantile regression, we estimated the lower limit of normal (LLN) for sural amplitudes to be 3 μV for patients 60-70 years, 1 μV for those 70-74 years, and <1 μV (absent) for those ≥75 years of age. IENFD and QSART volume were reduced with advancing age, although IENFD was lower in men and QSART volume was lower in women.

CONCLUSIONS

We propose that an absent sural SNAP in patients up to 75 years of age should be considered abnormal. Our findings also support age- and gender-stratified normative data for IENFD and QSART.