Small-fibre neuropathies--advances in diagnosis, pathophysiology and management.
Small-fibre neuropathy (SFN), a disorder of thinly myelinated Aδ-fibres and unmyelinated C-fibres, is clinically characterized by neuropathic pain symptoms and autonomic complaints. Diagnosis of SFN is challenging as the clinical picture can be difficult to interpret and results from nerve conduction studies are often normal. In cases of suspected SFN, measurement of intraepidermal nerve fibre density and/or analysis of quantitative sensory testing can enable diagnosis. New diagnostic techniques (including measurement of nerve fibre density using corneal confocal microscopy, and nociceptive evoked potentials) may contribute to the diagnostic work-up. SFN can be associated with systemic diseases such as immune-mediated disorders, but remains idiopathic in a substantial proportion of patients. Gain-of-function variants in the Na(v)1.7 sodium channel have recently been found in nearly 30% of patients with idiopathic SFN, but the mechanisms of axonal degeneration in the disorder remain under investigation. Identification of the systemic diseases underlying SFN will enable development of drugs that target affected pathways to improve the management of neuropathic pain and autonomic dysfunction. In this Review, we discuss recent advances in the diagnosis and pathophysiology of SFN, highlighting how improved understanding of these aspects of the disorder will contribute to better patient management.
Department of Neurology, University Medical Center Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands.
Janneke G
JG
Hoeijmakers
Catharina G
CG
Faber
Giuseppe
G
Lauria
Ingemar S
IS
Merkies
Stephen G
SG
Waxman
D005073:Evoked Potentials, Somatosensory; D006801:Humans; D009154:Mutation / Q000235:genetics; D062556:NAV1.7 Voltage-Gated Sodium Channel / Q000235:genetics; D009413:Nerve Fibers, Myelinated / Q000473:pathology / Q000502:physiology*; D036421:Nerve Fibers, Unmyelinated / Q000473:pathology / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D010146:Pain / Q000209:etiology; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics / Q000628:therapy*; D012684:Sensory Thresholds / Q000502:physiology
D062556:NAV1.7 Voltage-Gated Sodium Channel; C486866:SCN9A protein, human