Journal of Pain Research (Feb 2022)
Implications of Nerve Fiber Density on the Diagnosis and Treatment of Juvenile Fibromyalgia
Abstract
Nabeel Ahmed,1 Marie Vigouroux,2,3 Pablo Ingelmo3– 5 1Faculty of Medicine, McGill University, Montreal, QC, Canada; 2Faculty of Dentistry, McGill University, Montreal, QC, Canada; 3Edwards Family Interdisciplinary Center for Complex Pain, Montreal Children’s Hospital, Montreal, QC, Canada; 4Research Institute, McGill University Health Centre, Montreal, QC, Canada; 5Alan Edwards Research Center for Pain, McGill University, Montreal, QC, CanadaCorrespondence: Marie Vigouroux, Family Interdisciplinary Center for Complex Pain, Montreal Children’s Hospital, 1001 boul. Décarie A02.3523, Montreal, QC, H4A 3J1, Canada, Tel +1 514 412 4448, Fax +1 514 412 4341, Email [email protected]: Juvenile fibromyalgia (JFM) is a condition that presents as chronic widespread musculoskeletal pain and affects children and adolescents. JFM remains a challenging diagnosis, as it is both based on subjective criteria and the pathogenesis is poorly understood. Small fiber neuropathy (SFN) is a distinct condition, which is characterized by pathology of small A-delta and C fibers, and can present similarly to JFM. Small fiber pathology is characterized by reduced intraepidermal nerve fiber density (IENFD) on skin biopsy. Recent studies have found that as many as half of patients with JFM can demonstrate decreased IENFD, in pattern similar to SFN. This phenomenon has been referred to as small fiber pathology. The meaning of these findings was disputed; however, the current consensus remains that fibromyalgia and SFN are distinct conditions. Additionally, among patients with fibromyalgia, there are two phenotypes: those with small fiber pathology and those without. The purpose of this review was to characterize the role assessment of IENFD plays in the clinical context. We conducted a narrative review of pertinent articles pertaining to JFM, SFN and small fiber pathology in fibromyalgia. We concluded that assessment of IENFD should be completed if SFN is suspected either when a patient first presents or in patients who were previously diagnosed with fibromyalgia and SFN is later suspected. Distinguishing between JFM and SFN is important because recommended therapies differ between the two conditions. However, there is no evidence to support the use of skin biopsy to distinguish between the two discussed fibromyalgia phenotypes. More studies are needed to elucidate whether IENFD varies with morbidity and if both fibromyalgia phenotypes vary in their response to different therapeutic regimens.Keywords: small fiber neuropathy, skin biopsy, chronic pain, pediatric
