Small Nerve Fiber Dysfunction May Help Better Classify hEDS, HSD

Assessing these abnormalities may pinpoint potentially more effective therapies

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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small nerve fibers | Ehlers-Danlos News | illustration of patient experiencing pain

Signs of dysfunction in small nerve fibers, the nerve cells mainly responsible for detecting sensations like pain, are found in people with hypermobile Ehlers-Danlos syndrome (hEDS) or hypermobility spectrum disorder (HSD), according to a large retrospective study.

Assessing these abnormalities could help better classify people with hEDS or HSD based on the severity of their disease and identify potential therapeutic options, researchers say.

The study, “Small fiber neuropathy in hypermobile Ehlers Danlos Syndrome/Hypermobility Spectrum Disorder,” was published in the Journal of Internal Medicine.

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Previous research has indicated that some people with hEDS or HSD — hypermobile joints in people for whom EDS has been excluded as a diagnosis — show signs of small nerve fiber dysfunction, but these studies have mostly been limited to fewer than 20 patients.

In the study, a team led by scientists at the University of Lausanne in Switzerland reported on structural and functional evaluations of small nerve fibers in 56 people with hEDS and 23 with HSD. Patients underwent a standardized assessment including a clinical examination, questionnaires, and specific testing of small fiber function called quantitative sensory testing (QST). Patients reported at least moderate pain that routinely caused problems in their day-to-day life.

Based on QST measures, 55 of 79 patients (70%) showed signs of small nerve fiber dysfunction. Signs of abnormal nerve fiber structure were found in skin biopsies of 54 of 69 (78%) patients who underwent biopsies.

In the 69 patients who underwent both assessments, 40 (58%) showed definite signs of small fiber neuropathy (i.e., clear evidence of both physical damage and electrical dysfunction), while 23 (33%) had possible neuropathy — abnormal function and structure, but not both — and six patients showed no signs of small nerve fiber neuropathy.

“The large proportion of patients in this study displaying small nerve fiber abnormalities underscores the possible contribution of the peripheral nervous system to hEDS/HSD symptoms,” the researchers wrote. The peripheral nervous system encompasses all the nerves that run through the body outside the brain and spinal cord.

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“The presence of small fiber pathology could help a better stratification of the heterogeneous hEDS/HSD population in terms of severity, disease extent and therapeutic options,” the team added.

A limitation of this study is its retrospective design, and the fact that most of the participants were referred to the researchers’ clinic because they were experiencing symptoms indicative of small fiber dysfunction.

“Hence, the described cohort is not reflecting a full population of hEDS/HSD patients,” the researchers wrote. “The assessment of an entire cohort would allow determining more precisely the [small nerve damage] prevalence in a general population of hEDS/HSD, including those who are asymptomatic.”