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Silsby M, Feldman EL, Dortch RD, Roth A, Haroutounian S, Rajabally YA, Vucic S, Shy ME, Oaklander AL, Simon NG. Advances in diagnosis and management of distal sensory polyneuropathies. J Neurol Neurosurg Psychiatry 2023; 94:1025-1039. [PMID: 36997315 PMCID: PMC10544692 DOI: 10.1136/jnnp-2021-328489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 02/23/2023] [Indexed: 04/01/2023]
Abstract
Distal sensory polyneuropathy (DSP) is characterised by length-dependent, sensory-predominant symptoms and signs, including potentially disabling symmetric chronic pain, tingling and poor balance. Some patients also have or develop dysautonomia or motor involvement depending on whether large myelinated or small fibres are predominantly affected. Although highly prevalent, diagnosis and management can be challenging. While classic diabetes and toxic causes are well-recognised, there are increasingly diverse associations, including with dysimmune, rheumatological and neurodegenerative conditions. Approximately half of cases are initially considered idiopathic despite thorough evaluation, but often, the causes emerge later as new symptoms develop or testing advances, for instance with genetic approaches. Improving and standardising DSP metrics, as already accomplished for motor neuropathies, would permit in-clinic longitudinal tracking of natural history and treatment responses. Standardising phenotyping could advance research and facilitate trials of potential therapies, which lag so far. This review updates on recent advances and summarises current evidence for specific treatments.
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Affiliation(s)
- Matthew Silsby
- Neurology, Westmead Hospital, Westmead, New South Wales, Australia
- Brain and Nerve Research Centre, Sydney Medical School, The University of Sydney, New South Wales, Australia
| | - Eva L Feldman
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA
| | - Richard D Dortch
- Division of Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
| | - Alison Roth
- Division of Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA
| | - Simon Haroutounian
- Department of Anesthesiology, Washington University School of Medicine in Saint Louis, St Louis, Missouri, USA
| | - Yusuf A Rajabally
- Inflammatory Neuropathy Clinic, Department of Neurology, University Hospitals Birmingham, Aston Medical School, Aston University, Birmingham, UK
| | - Steve Vucic
- Brain and Nerve Research Centre, Sydney Medical School, The University of Sydney, New South Wales, Australia
| | - Michael E Shy
- Department of Neurology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Anne Louise Oaklander
- Nerve Unit, Departments of Neurology and Pathology (Neuropathology), Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Neil G Simon
- Northern Beaches Clinical School, Macquarie University, Frenchs Forest, New South Wales, Australia
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Chan ACY, Kumar S, Tan G, Wong HY, Ong JJY, Chandra B, Huang H, Sharma VK, Lai PS. Expanding the genetic causes of small-fiber neuropathy: SCN genes and beyond. Muscle Nerve 2023; 67:259-271. [PMID: 36448457 DOI: 10.1002/mus.27752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 10/31/2022] [Accepted: 11/06/2022] [Indexed: 12/05/2022]
Abstract
Small-fiber neuropathy (SFN) is a disorder that exclusively affects the small nerve fibers, sparing the large nerve fibers. Thinly myelinated Aδ-fibers and unmyelinated C-fibers are damaged, leading to development of neuropathic pain, thermal dysfunction, sensory symptoms, and autonomic disturbances. Although many SFNs are secondary and due to immunological causes or metabolic disturbances, the etiology is unknown in up to half of the patients. Over the years, this proportion of "idiopathic SFN" has decreased, as familial and genetic causes have been discovered, thus shifting a proportion of once "idiopathic" cases to the genetic category. After the discovery of SCN9A-gene variants in 2012, SCN10A and SCN11A variants have been found to be pathogenic in SFN. With improved accessibility of SFN diagnostic tools and genetic tests, many non-SCN variants and genetically inherited systemic diseases involving the small nerve fibers have also been described, but only scattered throughout the literature. There are 80 SCN variants described as causing SFN, 8 genes causing hereditary sensory autonomic neuropathies (HSAN) described with pure SFN, and at least 7 genes involved in genetically inherited systemic diseases associated with SFN. This systematic review aims to consolidate and provide an updated overview on the genetic variants of SFN to date---SCN genes and beyond. Awareness of these genetic causes of SFN is imperative for providing treatment directions, prognostication, and management of expectations for patients and their health-care providers.
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Affiliation(s)
- Amanda C Y Chan
- Division of Neurology, Department of Medicine, National University Hospital, Singapore, Singapore
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
| | - Shivaram Kumar
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
| | - Grace Tan
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
| | - Hiu Yi Wong
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China
- Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China
| | - Jonathan J Y Ong
- Division of Neurology, Department of Medicine, National University Hospital, Singapore, Singapore
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
| | - Bharatendu Chandra
- Division of Neurology, Department of Medicine, National University Hospital, Singapore, Singapore
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
- Division of Medical Genetics, University of Iowa, Iowa City, Iowa, USA
| | - Hua Huang
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
| | - Vijay Kumar Sharma
- Division of Neurology, Department of Medicine, National University Hospital, Singapore, Singapore
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
| | - Poh San Lai
- Yong Loo Ling School of Medicine, National University of Singapore, Singapore, Singapore
- Adjunct Faculty, Genome Institute of Singapore, Singapore, Singapore
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Dormer A, Narayanan M, Schentag J, Achinko D, Norman E, Kerrigan J, Jay G, Heydorn W. A Review of the Therapeutic Targeting of SCN9A and Nav1.7 for Pain Relief in Current Human Clinical Trials. J Pain Res 2023; 16:1487-1498. [PMID: 37168847 PMCID: PMC10166096 DOI: 10.2147/jpr.s388896] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 03/14/2023] [Indexed: 05/13/2023] Open
Abstract
Introduction There is a great need to find alternative treatments for chronic pain which have become a healthcare problem. We discuss current therapeutic targeting Nav1.7. Areas Covered Nav1.7 is a sodium ion channel protein that is associated with several human pain genetic syndromes. It has been found that mutations associated with Nav1.7 lead to the loss of the ability to perceive pain in individuals that are otherwise normal. Several therapeutic interventions are presently undergoing preclinical and research using the methodology of damping Nav1.7 expressions as a methodology to decrease the sensation of pain leading to analgesia. Expert Opinion It is our strong belief that there is a viable future in the targeting of protein of Nav1.7 for the relief of chronic pain in humans. The review will look at the genomics associated with SCN1A and proteomic of Nav1.7 as a foundation to explain the mechanism of the therapeutic interventions targeting Nav1.7, the human disease that are associated with Nav1.7, and the current development of treatment for chronic pain whether in preclinical or clinical trials targeting Nav1.7 expressions. The development of therapeutic antagonists targeting Nav1.7 could be a viable alternative to the current treatments which have led to the opioid crisis. Therefore, Nav1.7 targeted treatment has a major clinical significance that will have positive consequences as it relates to chronic pain interventions.
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Affiliation(s)
- Anton Dormer
- Research and Development, Pepvax, Inc, Silver Spring, MD, USA
- Correspondence: Anton Dormer, Research and Development, PepVax, Inc, 8720 Georgia Ave #1000, Silver Spring, MD, 20910, USA, Email
| | | | - Jerome Schentag
- Research and Development, Pepvax, Inc, Silver Spring, MD, USA
| | - Daniel Achinko
- Research and Development, Pepvax, Inc, Silver Spring, MD, USA
| | - Elton Norman
- Research and Development, Pepvax, Inc, Silver Spring, MD, USA
| | - James Kerrigan
- Research and Development, Navintus, Inc, Princeton, NJ, USA
| | - Gary Jay
- Research and Development, Navintus, Inc, Princeton, NJ, USA
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Finsterer J, Scorza FA. Small fiber neuropathy. Acta Neurol Scand 2022; 145:493-503. [PMID: 35130356 DOI: 10.1111/ane.13591] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 01/19/2022] [Accepted: 01/24/2022] [Indexed: 11/01/2022]
Abstract
Small fiber neuropathy (SFN) is a peripheral nervous system disease due to affection of A-delta or C-fibers in a proximal, distal, or diffuse distribution. Selective SFN (without large fiber affection) manifests with pain, sensory disturbances, or autonomic dysfunction. Though uniform diagnostic criteria are unavailable, most of them request typical clinical features and reduced intra-epidermal nerve fiber density on proximal or distal skin biopsy. Little consensus has been reached about the treatment of SFN, why this narrative review aims at summarizing and discussing treatment options for SFN. Treatment of SFN can be classified as symptomatic, pathophysiologic, or causal. Prerequisites for treating SFN are an established diagnosis, knowledge about the symptoms and signs, and the etiology. Pain usually responds to oral/intravenous pain killers, antidepressants, anti-seizure drugs, or topical, transdermal specifications. Some of the autonomic disturbances respond favorably to symptomatic treatment. SFN related to Fabry disease or hATTR are accessible to pathogenesis-related therapy. Immune-mediated SFN responds to immunosuppression or immune-modulation. Several of the secondary SFNs respond to causal treatment of the underlying disorder. In conclusion, treatment of SFN relies on a multimodal concept and includes causative, pathophysiologic, and symptomatic measures. It strongly depends on the clinical presentation, diagnosis, and etiology, why it is crucial before initiation of treatment to fix the diagnosis and etiology. Due to the heterogeneous clinical presentation and multi-causality, treatment of SFN should be individualized with the goal of controlling the underlying cause, alleviating pain, and optimizing functionality.
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Affiliation(s)
- Josef Finsterer
- Neurology & Neurophysiology Center Vienna Austria
- Disciplina de Neurociência Escola Paulista de Medicina/Universidade Federal de São Paulo/. (EPM/UNIFESP) São Paulo Brasil
| | - Fulvio A. Scorza
- Disciplina de Neurociência Escola Paulista de Medicina/Universidade Federal de São Paulo/. (EPM/UNIFESP) São Paulo Brasil
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Bailly F. The challenge of differentiating fibromyalgia from small-fiber neuropathy in clinical practice. Joint Bone Spine 2021; 88:105232. [PMID: 34082128 DOI: 10.1016/j.jbspin.2021.105232] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 05/10/2021] [Indexed: 11/18/2022]
Abstract
Fibromyalgia and small fibre neuropathy are two diseases leading to chronic widespread pain, and it is difficult to differentiate them in order to provide appropriate care. In this review, we will describe the pathophysiological and clinical differences between fibromyalgia and small fibre neuropathy. In fibromyalgia, pain is increased by dysregulation of central pain processing while small fibre neuropathy pain is related to loss or dysfunction of intraepidermal small nerve fibres. Higher pain intensity; stabbing pain and paraesthesia; allodynia; dry eyes/mouth; changed pattern or sweating on body; skin colour alterations/modifications; reduced hair/nail growth on lower extremities; warm or cold hypoesthesia could be more common in small fibre neuropathy whereas headache or temporo-mandibular disorder point toward fibromyalgia. Length-dependent distribution of pain is common in small fibre neuropathy but can also affect the whole body. Anxiety or depression are common in these two diseases, but post-traumatic stress disorder and physical or sexual abuse in childhood or adulthood suggest fibromyalgia. Inflammatory disease or musculoskeletal disease is frequently reported with fibromyalgia whereas metabolic disorders (especially diabetes mellitus), neurotoxic exposure, Sjogren's syndrome, sarcoidosis, HIV are the main diseases associated with small fibre neuropathy. Skin biopsy, quantitative sensory testing, laser evoked potentials, confocal corneal microscopy or electrochemical skin conductance can help to discriminate between fibromyalgia and small fibre neuropathy.
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Affiliation(s)
- Florian Bailly
- Hôpital Pitié Salpêtrière - Assistance Publique Hôpitaux de Paris, Rheumatology department, Pain unit, 47-83, boulevard de l'hôpital, 75013 Paris, France.
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Acute monophasic erythromelalgia pain in five children diagnosed as small-fiber neuropathy. Eur J Paediatr Neurol 2020; 28:198-204. [PMID: 32723684 PMCID: PMC10021072 DOI: 10.1016/j.ejpn.2020.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 05/01/2020] [Accepted: 06/08/2020] [Indexed: 02/01/2023]
Abstract
The small-fiber polyneuropathies (SFN) are a class of diseases in which the small thin myelinated (Aδ) and/or unmyelinated (C) fibers within peripheral nerves malfunction and can degenerate. SFN usually begins in the farthest, most-vulnerable axons, so distal neuropathic pain and symptoms from microvascular dysregulation are common. It is well known in adults, e.g. from diabetes, human immunodeficiency virus, or neurotoxins, but considered extremely rare in children, linked mostly with pathogenic genetic variants in voltage-gated sodium channels. However, increasing evidence suggests that pediatric SFN is not rare, and that dysimmunity is the most common cause. Because most pediatric neurologists are unfamiliar with SFN, we report the diagnosis and management of 5 Swiss children, aged 6-11y, who presented with severe paroxysmal burning pain in the hands and feet temporarily relieved by cooling-the erythromelalgia presentation. Medical evaluations revealed autoimmune diseases in 3 families and 3/5 had preceding or concomitant infections. The standard diagnostic test (PGP9.5-immunolabeled lower-leg skin biopsy) confirmed SFN diagnoses in 3/4, and autonomic function testing (AFT) was abnormal in 2/3. Blood testing for etiology was unrevealing, including genetic testing in 3. Paracetamol and ibuprofen were ineffective. Two children responded to gabapentin plus mexiletine, one to carbamazepine, two to mexiletine plus immunotherapy (methylprednisolone/IVIg). All recovered within 6 months, remaining well for years. These monophasic tempos and therapeutic responses are most consistent with acute post-infectious immune-mediated causality akin to Guillain-Barré large-fiber polyneuropathy. Skin biopsy and AFT for SFN, neuropathic-pain medications and immunotherapy should be considered for acute sporadic pediatric erythromelalgia.
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