Autonomic evaluation is independent of somatic evaluation for small fiber neuropathy

• Relationship between somatic and autonomic evaluation in SFN is uncertain.
• We compared somatic and autonomic evaluation in SFN to evaluate the correlation.
• There was no correlation between autonomic function and sensory measures.
• Weak correlations were noted among some modalities of small fiber sensory measures.
• Autonomic and sensory outcomes are independent but complementary measures of SFN.

BackgroundThe relationship between the autonomic reflex screening test (ARS) and measures of sensory function and structure (quantitative sensory testing (QST) and intraepidermal nerve fiber density (IENFD)) remains uncertain in patients with distal small fiber neuropathy (SFN). The aim of this study was to evaluate the correlations among a range of autonomic (quantitative sudomotor axon reflex test (QSART), cardiovagal and cardio adrenergic tests and the composite autonomic severity score (CASS)) and somatic sensory measures (QST of vibration, cooling and heat-pain thresholds and IENFD).Method122 patients with clinically suspected sensory neuropathy without motor weakness and with normal nerve conduction studies underwent blinded autonomic reflex screening test (ARS), quantitative sensory testing (QST) and skin biopsy (IENFD) for diagnosis of SFN. The relationship between autonomic and somatic sensory measures was assessed.ResultsThere was no association between autonomic function measures (QSART volume, CASS_QSART, CASS_vagal, CASS_adrenergic or total CASS) and small fiber sensory measures (IENFD, cooling or heat-pain thresholds). Weak correlations were noted among some modalities of QST (vibration and cooling thresholds) and IENFD.DiscussionAutonomic and sensory outcomes are independent (complementary) measures of distal SFN, and should where feasible be used concurrently in the evaluation of SFN.