Background

Small fibre neuropathy (SFN) is characterized by neuropathic sensory abnormalities and autonomic dysfunction. Patients often experience burning pain, tingling, or other sensory disturbances, alongside autonomic symptoms such as postural dizziness, gastrointestinal dysfunction (e.g., nausea, bloating), and cardiovascular irregularities. This study evaluates the prevalence and patterns of sensory and autonomic symptoms in SFN and their associations with microneurography findings and autonomic function test abnormalities.

Methods

A retrospective study was conducted on 101 patients referred for microneurography and/or autonomic function testing at King’s College Hospital. Patients with neuropathic sensory abnormalities, including pain, and/or autonomic dysfunction were included, while those with confirmed large fibre neuropathy were excluded. Microneurography assessed nociceptor and sympathetic fibre dysfunction. Autonomic function testing evaluated splanchnic sympathetic function, blood vessel resistance during isometric grip, cardiac accelerator function during isometric exercise, and Mayer Waves. Associations between neuropathic symptoms, microneurography findings, and autonomic dysfunction were analyzed using Chi-Square and Fisher’s Exact tests, with Bonferroni correction (adjusted α = 0.003).

Results

The cohort was predominantly female (87 patients, 86%), with a median age of 41 years. Neuropathic sensory symptoms were present in 76 patients (75%), with 46 (46%) experiencing length-dependent and 55 (54%) non-length-dependent patterns. Autonomic symptoms were widespread, with 76 (75%) reporting more than two autonomic disturbances, including postural dizziness (92, 91%), gastrointestinal dysfunction (81, 80%), bladder dysfunction (65, 64%), respiratory abnormalities (48, 48%), and sweating disturbances (46, 46%). Fibromyalgia was reported in 48 (48%), fatigue in 56 (55%), and mast cell activation syndrome in 40 (40%).

Microneurography abnormalities were found in 99 cases (98%), with nociceptor dysfunction in 68 (67%) and sympathetic fibre abnormalities in 58 (57%). Neuropathic sensory symptoms significantly correlated with nociceptor abnormalities (73, 72%, p < 0.001, Phi & Cramer’s V = 0.376). Among patients with autonomic symptoms, 65 (64%) had sympathetic fibre abnormalities, but no direct correlation was found between sympathetic fibre abnormalities and autonomic symptoms. Autonomic function testing (performed in 67 patients, 66%) revealed abnormalities in 82 (81%), including splanchnic dysfunction (55, 54%), Mayer Waves (46, 46%), and impaired cardiac accelerator function (53, 52%).

Conclusion

Neuropathic sensory symptoms were strongly associated with nociceptor dysfunction, whereas autonomic symptoms were widespread but not directly linked to sympathetic fibre abnormalities. Further research is needed to refine diagnostic criteria, explore potential biomarkers, and better understand the pathophysiology of autonomic dysfunction in SFN.