22. Laser evoked potentials, skin biopsy, somatosensory evoked potentials and electroneurography to evaluate small nerve fiber dysfunction in small fibers neuropathy: A preliminary study

Abstract

Small fiber neuropathy (SFN) is characterized by a predominantly damage of small myelinated (A δ ) or unmyelinated C fibers. The specific fiber types involved in this process include both small somatic and autonomic fibers. The abnormalities of these fibers may differ in SFN and the diagnostic reliability of somatic vs autonomic functions has not been well established in patients with suspected SFN. We recruited 6 patients with suspected SFN including somatic and autonomic symptoms and normal large myelinated fibers function evaluated by means of electroneurography (ENG) and somatosensory evoked potentials (2 pz). We carried out leg skin biopsy and laser evoked potentials (LEPs) to verify a possible diagnostic reliability of these tests. In all patients skin biopsy showed somatic and autonomic SFN small fiber neuropathy, 5 of them (83%) showed altered foot LEPs with absent signal of N2-P2 cortical responses. Our data demonstrated a reasonable concordance between LEP and skin biopsy in evaluating small nerve fiber loss in SFN. However these data should be considered preliminary and a larger number of patients must be recruited before to draw any definite conclusion.