Idiopathic distal sensory polyneuropathy

Abstract

Objective:To present standardized diagnostic criteria for idiopathic distal sensory polyneuropathy (iDSP) and its subtypes: idiopathic mixed fiber sensory neuropathy (iMFN), idiopathic small fiber sensory neuropathy (iSFN), and idiopathic large fiber sensory neuropathy (iLFN) for use in research.Methods:The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities and Networks (ACTTION) public-private partnership with the Food and Drug Administration convened a meeting to develop consensus diagnostic criteria for iMFN, iSFN, and iLFN. After background presentations, a collaborative, iterative approach was used to develop expert consensus for new criteria.Results:An iDSP diagnosis requires at least one small fiber (SF) or large fiber (LF) symptom, at least one SF or LF sign, abnormalities in sensory nerve conduction studies (NCS) or distal intra-epidermal nerve fiber density (IENFD), and exclusion of known etiologies. An iMFN diagnosis requires that at least one of the above clinical features is SF and one clinical feature is LF. Diagnostic criteria for iSFN require at least one SF symptom and at least one SF sign with abnormal IENFD, normal sensory NCS, and the absence of LF symptoms and signs. Diagnostic criteria for iLFN require at least one LF symptom and at least one LF sign with normal IENFD, abnormal NCS, and absence of SF symptoms and signs.Conclusions:Adoption of these standardized diagnostic criteria will advance research and clinical trials and spur development of novel therapies for iDSPs..

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“…21 The SFN diagnosis is confirmed by abnormally low densities of PGP9.5-immunolabeled epidermal neurites in lower-leg skin biopsies (#5% of predicted), which is recommended for research inclusion. 27 Given the personal disability and high medical and societal costs of ME/CFS, the identification of potential pathophysiological contributors is of major importance. 26 Studies of varying quality link ME/CFS to preceding infections, immune system disorders, adrenal insufficiency, and various causes of autonomic nervous system function.…”

“…47 However, tradeoffs include lower sensitivity (58%) 47 than more comprehensive testing such as autonomic function testing, which is not endorsed because of lower specificity, higher complexity of administration and interpretation, and limited availability. 27 Another reason for low sensitivity is that axonal degeneration is an end-stage change, whereas earlier small fiber malfunction also contributes but is harder to quantify. 48 Lower leg biopsies are less sensitive for patchy, proximal, or non-length-dependent SFN, and in fibromyalgia, wider areas used in biopsies identified proximal denervation as more prevalent (46% in upperthigh biopsy specimens vs 32% in distal-leg biopsies).…”

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“…Diagnostic criteria for idiopathic SFN has been proposed in 2020, based on expert consensus [29]. A diagnosis requires the presence of one characteristic painful or non-painful SFN (e.g., spontaneous or intermittent pain, paresthesias) present in a symmetrical, length-dependent distribution, at least one small fiber sign on the basis of a physical examination (e.g., allodynia, hyperalgesia, abnormal pinprick perception), absence of muscle weakness, absence of diseases with neurological impairment and abnormalities in IENFD skin biopsy or sensory nerve conduction studies and a disease duration of at least 3 months 4.…”