Acute steroid responsive small-fiber sensory neuropathy: a new entity?

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Acute steroid responsive small-fiber sensory neuropathy: a new entity?
Dabby R1, Gilad R, Sadeh M, Lampl Y, Watemberg N.

2006
Abstract
Small-fiber neuropathy is often idiopathic and commonly follows a chronic course. Treatment is often effective in treating the core symptom of pain, but it has no effect on the pathologic process. We describe four patients with acute small-fiber neuropathy who responded dramatically to steroid therapy. All patients had acute onset neuropathic pain, normal nerve conduction studies, and evidence of small-fiber dysfunction in quantitative sensory testing and skin biopsy. Symptoms were distal and symmetrical in three patients and generalized in one patient. In two cases, the neuropathy presented as an erythromelalgia-like syndrome. Marked clinical improvement occurred 1-2 weeks after oral prednisone therapy was initiated. Three patients remained symptom free, and one patient experienced recurrence of neuropathy after prednisone was tapered.

 

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DR ANNE LOUISE OAKLANDER 2020


Chapter 10 - Dysimmune small fiber neuropathies

https://doi.org/10.1016/B978-0-12-814572-2.00010-8Get rights and content

Abstract

Small-fiber polyneuropathy (SFN) consists of exclusive or preferential damage to very thin A-delta and thinner sensory and autonomic/trophic C-fibers, the most vulnerable axons.

Lack of myelination and a high axolemma/axoplasm ratio leave their distal neurites most likely to malfunction and degenerate in suboptimal conditions.

SFN’s cardinal symptoms—symmetric neuropathic pain and itch, postexertional fatigue, postural orthostasis, and postprandial gastrointestinal distress—are so nonspecific that confirmation with PGP9.5-immunolabeled skin biopsies is recommended for uncertain cases.

Sensory symptoms reflect excess axonal firing plus deafferentation of central inhibitory circuits.

Internal symptoms also reflect premature hypoxia and impaired cardiac return from malfunctioning sympathomotor blood-vessel regulation.

With half of fibromyalgia patients having evidence of SFN, it could be the most common peripheral neuropathy, but currently, SFN symptoms are often managed palliatively leaving the SFN undiagnosed and untreated, particularly in children.

Among the many patients without diabetes or evidence cause (initially idiopathic SFN/iiSFN), dysimmunity is increasingly implicated.

Almost all nonlength-dependent iiSFN (sensory and/or autonomic ganglionitis/neuronitis) is autoantibody-mediated, with Sjögren’s syndrome most common.
B-cells also appear involved in acute, Guillain-Barré-like and chronic length-dependent iiSFN, akin to chronic inflammatory demyelinating polyneuropathy.

A large series documents elevated prevalences of immune markers, and a passive-transfer experiment reproduced iiSFN behaviorally and pathologically in mice injected with patient sera.

A small case series documents the responsiveness of apparently dysimmune SFN to corticosteroids, with four larger series reporting efficacy of intravenous immunoglobulins (IVIg).

For immune-mediated SFN, pain management alone is only marginally effective, and it permits damage to continue, risking disability and medication dependence.

In contrast, immunomodulation not only can improve symptoms, but also reduce medication use and encourage small-fiber regrowth and recovery.

When SFN is arrested, the prognosis is good for restoring life quality and trajectory, particularly in young and otherwise healthy patients.

Hence, the need to improve the diagnosis and treatment of dysimmune SFN.