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Small fiber neuropathy ( SFN) is a disorder typically dominated by neuropathic pain and autonomic dysfunction, in which the thinly myelinated Aδ-fibers and unmyelinated C-fibers are selectively injured. The diagnosis SFN is based on a reduced intraepidermal nerve fiber density and/or abnormal thermal thresholds in quantitative sensory testing. The etiologies of SFN are diverse, although no apparent cause is frequently seen. Recently, SCN9A-gene variants (single amino acid substitutions) have been found in ∼30% of a cohort of idiopathic SFN patients, producing gain-of-function changes in sodium channel NaV1.7, which is preferentially expressed in small diameter peripheral axons. Functional testing showed that these variants altered fast inactivation, slow inactivation or resurgent current and rendered dorsal root ganglion neurons hyperexcitable. In this review, we discuss the role of NaV1.7 in pain and highlight the molecular genetics and pathophysiology of SCN9A-gene variants in SFN. With increasing knowledge regarding the underlying pathophysiology in SFN, the development of specific treatment in these patients seems a logical target for future studies. [ABSTRACT FROM AUTHOR]

Objective: Fatigue is a major complaint in patients with immune mediated polyneuropathies. Despite apparently good physical recovery after Guillain-Barré syndrome (GBS), many patients remain restricted in daily and social activities, and have a decreased quality of life. In this trial, the effect of amantadine on severe fatigue related to GBS was studied.Methods: During the pre-treatment phase, all patients were monitored for 2 weeks. Only patients with severe fatigue, defined as a mean fatigue score of > or = 5.0 on the Fatigue Severity Scale (FSS), were randomised for this double blind, placebo controlled, crossover study. Primary outcome measure was improvement of at least 1 point on the FSS. Secondary outcome measures were impact of fatigue, anxiety and depression, handicap, and quality of life.Results: In total, 80 patients with GBS were randomised, of whom 74 were included for analysis. Fatigue appeared to be reduced already during the pre-treatment phase (p = 0.05), probably due to increased attention provided to the patients. No significant differences in any of the primary and secondary outcome measures were found.Conclusions: Amantadine was not superior to placebo. Because fatigue remains a serious complaint, other studies evaluating new treatment options are strongly recommended. [ABSTRACT FROM AUTHOR]