ABSTRACT
The clinical spectrum of small fiber neuropathy (SFN) encompasses manifestations related to the involvement of thinly myelinated A-delta and unmyelinated C fibers, including not only the classical distal phenotype, but also a non-length-dependent (NLD) presentation that can be patchy, asymmetrical, upper limb-predominant, or diffuse. This narrative review is focused on NLD-SFN. The diagnosis of NLD-SFN can be problematic, due to its varied and often atypical presentation, and diagnostic criteria developed for distal SFN are not suitable for NLD-SFN. The topographic pattern of NLD-SFN is likely related to ganglionopathy restricted to the small neurons of dorsal root ganglia. It is often associated with systemic diseases, but about half the time is idiopathic. In comparison with distal SFN, immune-mediated diseases are more common than dysmetabolic conditions. Treatment is usually based on the management of neuropathic pain. Disease-modifying therapy, including immunotherapy, may be effective in patients with identified causes. Future research on NLD-SFN is expected to further clarify the interconnected aspects of phenotypic characterization, diagnostic criteria, and pathophysiology.
Subject(s)
Neuralgia , Small Fiber Neuropathy , Ganglia, Spinal , Humans , Nerve Fibers, Unmyelinated , Neuralgia/diagnosis , Neuralgia/etiology , Neuralgia/therapy , Small Fiber Neuropathy/diagnosis , Small Fiber Neuropathy/etiology , Small Fiber Neuropathy/therapyABSTRACT
We report the features of non-length dependent small fiber neuropathy (SFN) and compare them to those with distal length-dependent SFN. In a series of 224 consecutive neuropathy patients, we evaluated 44 patients with SFN diagnosed in the presence of both symptoms and signs. Eleven were classified as non-length dependent SFN. Disease associations were Sjögren's syndrome (two patients), impaired glucose tolerance, rheumatoid arthritis, hepatitis C virus, Crohn's disease, and idiopathic (five patients). In the 33 patients with distal SFN, the age of onset was significantly older and more had impaired glucose metabolism (16/33). In both groups, pain was mainly characterized as burning, but patients with non-length dependent SFN more often reported an "itchy" quality and allodynia to light touch.