title: Small fiber neuropathy in women with fibromyalgia. An in vivo assessment using corneal confocal bio-microscopy.
abstract: OBJECTIVE
  A consistent line of investigation suggests that fibromyalgia is a neuropathic pain syndrome. This outlook has been recently reinforced by several controlled studies that describe decreased small nerve fiber density in skin biopsies of patients with fibromyalgia. The cornea receives the densest small fiber innervation of the body. Corneal confocal bio-microscopy is a new noninvasive method to evaluate small nerve fiber morphology. Our objective was to assess corneal small nerve fiber morphology in patients with fibromyalgia, and to associate corneal nerve microscopic features with neuropathic pain descriptors and other fibromyalgia symptoms.
  
  
  METHODS
  We studied 17 female patients with fibromyalgia and 17 age-matched healthy control subjects. All the participants completed different questionnaires regarding the symptoms of fibromyalgia, including a neuropathic pain survey. A central corneal thickness scan was obtained with a confocal microscope. Nerve measurements were made by a single ophthalmologist without knowledge of the clinical diagnosis. Stromal nerve thickness was defined as the mean value between the widest and the narrowest portion of each analyzed stromal nerve. Corneal sub-basal plexus nerve density was also assessed.
  
  
  RESULTS
  Patients with fibromyalgia had stromal nerve thickness of 5.0 ± 1.0 µm (mean ± standard deviation) significantly different from that of control's values (6.1 ± 1.3) p = 0.01. Patients also had decreased sub-basal plexus nerve density per square millimeter (85 ± 29) vs. 107 ± 26 of controls p = 0.02. When controls and patients were grouped together, there was an association between stromal nerve slenderness and neuropathic pain descriptors (Fisher's exact test p = 0.007).
  
  
  CONCLUSIONS
  Women suffering from fibromyalgia have thinner corneal stromal nerves and diminished sub-basal plexus nerve density when compared to healthy controls. Nerve scarcity is associated with neuropathic pain descriptors. Small fiber neuropathy may play a role in the pathogenesis of fibromyalgia pain. Corneal confocal microscopy could become a useful test in the study of patients with fibromyalgia.
authors.affiliation: Asociación para Evitar la Ceguera, Mexico, México.
authors.forename: Manuel
authors.initials: M
authors.lastname: Ramírez
authors.affiliation: Instituto Nacional de Cardiología Ignacio Chávez, Periferico Sur y Viaducto Tlalpan, Mexico, México.
authors.forename: Laura-Aline
authors.initials: LA
authors.lastname: Martínez-Martínez
authors.affiliation: Asociación para Evitar la Ceguera, Mexico, México.
authors.forename: Everardo
authors.initials: E
authors.lastname: Hernández-Quintela
authors.affiliation: Asociación para Evitar la Ceguera, Mexico, México.
authors.forename: Jorge
authors.initials: J
authors.lastname: Velazco-Casapía
authors.affiliation: Instituto Nacional de Cardiología Ignacio Chávez, Periferico Sur y Viaducto Tlalpan, Mexico, México.
authors.forename: Angélica
authors.initials: A
authors.lastname: Vargas
authors.affiliation: Instituto Nacional de Cardiología Ignacio Chávez, Periferico Sur y Viaducto Tlalpan, Mexico, México. Electronic address: drmartinezlavin@gmail.com.
authors.forename: Manuel
authors.initials: M
authors.lastname: Martínez-Lavín
mesh_terms: D000328:Adult; D003315:Cornea / Q000294:innervation* / Q000473:pathology; D004916:Erythromelalgia / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D005356:Fibromyalgia / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D018613:Microscopy, Confocal; D008875:Middle Aged; D010147:Pain Measurement; D012720:Severity of Illness Index
keywords: Corneal confocal microscopy; Dorsal root ganglia; Fibromyalgia; Neuropathic pain; Small fiber neuropathy; Sympathetic pain